12M Series 3, 140M Series 3 and 160M Series 3 Motor Graders Caterpillar


Sensor Signal (PWM) - Test

Usage:

12M 3 AWD N9B

Joystick PWM Sensor Codes

Transmission ECM

The following is a list of diagnostic codes that are associated with the (Joystick) PWM Sensors of the machine.

Table 1
Transmission ECM (MID 27)    
DTC     Code Description     System Response    
1471-2     Steering Control Position Sensor #1: Data Erratic, Intermittent, or Incorrect     A Warning Level 3 Will Be Generated.    
1471-3     Steering Control Position Sensor #1: Voltage above normal     A Warning Level 3 Will Be Generated.    
1471-4     Steering Control Position Sensor #1: Voltage Below Normal     A Warning Level 3 Will Be Generated.    
1471-8     Steering Control Position Sensor #1: Abnormal Frequency, Pulse Width, or Period     A Warning Level 3 Will Be Generated.    
1471-14     Steering Control Position Sensor #1: Special Instruction     A Warning Level 3 Will Be Generated.    
1472-2     Steering Control Position Sensor #2: Data Erratic, Intermittent, or Incorrect     A Warning Level 3 Will Be Generated.    
1472-3     Steering Control Position Sensor #2: Voltage above normal     A Warning Level 3 Will Be Generated.    
1472-4     Steering Control Position Sensor #2: Voltage Below Normal     A Warning Level 3 Will Be Generated.    
1472-8     Steering Control Position Sensor #2: Abnormal Frequency, Pulse Width, or Period     A Warning Level 3 Will Be Generated.    
1472-14     Steering Control Position Sensor #2: Special Instruction     A Warning Level 3 Will Be Generated.    
1473-2     Steering Control Position Sensor #3: Data Erratic, Intermittent, or Incorrect     A Warning Level 3 Will Be Generated.    
1473-3     Steering Control Position Sensor #3: Voltage above normal     A Warning Level 3 Will Be Generated.    
1473-4     Steering Control Position Sensor #3: Voltage Below Normal     A Warning Level 3 Will Be Generated.    
1473-8     Steering Control Position Sensor #3: Abnormal Frequency, Pulse Width, or Period     A Warning Level 3 Will Be Generated.    
1473-14     Steering Control Position Sensor #3: Special Instruction     A Warning Level 3 Will Be Generated.    

Pulse Width Modulation (PWM) is a technique for controlling analog circuits with digital outputs. PWM is employed in various applications ranging from measurement to communication with the Electronic Control Module (ECM). The duty cycle of a square wave is modulated to encode a specific analog signal level. The duty cycle is the ratio of the on-time to the period. The modulating frequency is the inverse of the period. The duty cycle is programmed into the software of the ECU. The engineer (or programmer) sets the period in the on-chip timer counter that provides the modulating square wave. The engineer sets the direction of the PWM output along with the on-time in the PWM control register.

One of the advantages of the PWM sensor is that the signal remains digital all the way from the ECM to the controlled system. No digital to analog conversion is necessary. By using a digital signal, noise effects are minimized. Noise affects a digital signal if the noise can change a logic 1 to a logic 0 or a logic 0 to a logic 1.

Operation of the Left Joystick




Illustration 1g01487634

Power supply and ground assignments for internal components of the left joystick

Note: The illustration above shows the various power and ground assignments for the left joystick. If a component in the joystick has failed, replace the Left Hand Joystick faceplate. For Joystick faceplate replacement, refer to Special Instruction, REHS7448, "Procedure to remove and replace the Left-Hand Joystick Push-Button Faceplate on M Series, M Series 2, and M Series 3 Motor Graders".The illustration is displayed to aid in the troubleshooting of the component and circuit. For a complete connection diagram for all of the joystick to ECM connections, refer to the System Schematics in the back of this manual.

All of the internal components and the harness circuits have assigned diagnostic codes. The Implement ECM will activate the diagnostic code for a component when an abnormal condition is detected in the involved circuit.

Two ground sources are connected to all of the internal components of the joystick. Both ground circuits must fail, either internally or externally, for the component not to function due to a loss of the ground connections.

Possible Causes for an FMI 2 Diagnostic code are:

  • The sensor has failed.

  • An Intermittent connection exists in the sensor circuit.

  • The signal circuit is shorted to another circuit in the machine harness.

  • The sensor has failed.

  • The ECM has failed. ECM failure is unlikely.

Consider the following points when this code is active:

  • Use Cat ET to determine if an MID 145 CID 41 diagnostic code is active. If the diagnostic code for the 8 VDC power supply is active, fix the problem before proceeding.

  • The Transmission/Chassis ECM (MID 27) and the Implement ECM 2 (MID 145) receive an input signal from the "Steering Sensor 1". Both ECM modules can activate an FMI 2 diagnostic code when the signal is erratic or intermittent.

  • When only one of the ECM modules has an active FMI 2 diagnostic code, the probability is that the sensor is operating correctly. When this condition occurs, a poor connection in the machine harness would be suspected.

  • When both ECM modules have activated the diagnostic code, either the sensor or a harness problem may be the cause.

  • If both ECM modules have activated the diagnostic code, either ECM is probably not the cause the problem.

  • For either condition, proceed with this procedure to verify the cause of the problem.


Possible Causes for an FMI 3 Diagnostic code are:

  • The sensor supply or the ground circuit in the machine harness is open.

  • The signal circuit in the machine harness is shorted to the +battery.

  • The signal circuit in the machine harness is open or the sensor is disconnected.

  • The sensor has failed.

  • The Transmission ECM has failed. A failure of the ECM is unlikely.

Possible Causes for an FMI 4 Diagnostic code are:

  • The sensor has failed.

  • The signal circuit in the machine harness is shorted to ground.

  • The Transmission ECM has failed. A failure of the ECM is unlikely

Possible Causes for an FMI 8 Diagnostic code are:

  • The sensor has failed

  • Intermittent connections or poor connections

  • The spacing of the sensor is incorrect

  • Mechanical devices are loose

  • Incorrect software is loaded to the ECM

  • The ECM has failed. ECM failure is unlikely

Possible Causes for an FMI 14 Diagnostic code are:

  • The sensor has failed.

  • The ECM has failed. A failure of the Transmission/Chassis ECM is unlikely.

Three steering position sensors are required for correct operation of the steering control. The steering position sensors are located in the left joystick assembly. Each sensor provides an input signal to the Implement ECM 2 and to the "Transmission/Chassis ECM". The ECM expects the input signals from all three steering position sensors to match closely. The FMI 14 diagnostic indicates that the sensor input signal does not match the other two sensors. The Transmission/Chassis ECM determines the status of the input signals from the three steering sensors. The code is active when "Steering Sensors" do not match another sensor but still matches the third sensor.

The "Steering Position Sensors 1 and 2" receive power from the 8 VDC power supply of the Implement ECM 2. The "Steering Position Sensor 3" receives power from the 8 VDC power supply of the Transmission/Chassis ECM. The "Steering Position Sensors" are internally connected to the ground at both ECM modules. The steering sensor must lose both grounds in order to lose a ground connection. The illustration above indicates the power and ground connections for the "Steer Sensors".

The position sensor is a PWM sensor that operates at a frequency of approximately 500 ± 80 Hz. The position sensor sends a PWM input signal to the Implement ECM 2 and to the "Transmission/Chassis ECM". The duty cycle will vary from 10% at the lever full left position to 90% at the lever full right position. When the lever is in the center position, the duty cycle will be approximately 50%.

Note: If an MID 082 CID 41 diagnostic code is active, fix the problem before proceeding with this procedure.

Note: The correct operating temperature range for the steering sensors is −40 °C (−40.0 °F) to 75 °C (167.0 °F). Return the temperature in the cab to normal when the cab temperature is extreme resulting in an FMI 03 or FMI 08 diagnostic code. An FMI 14 diagnostic code is also possible in these circumstances. Returning the temperature in the cab to a normal temperature will keep the steering position sensors operating in the acceptable temperature range. After stabilization of the temperature, verify that the FMI 14 diagnostic code is active before performing this procedure.

Note: The "Transmission/Chassis ECM" (MID 27) and the Implement ECM 2 (MID 82) receive an input signal from the "Steering Sensors". Both ECM modules can activate an FMI 14 diagnostic code. The code is activated when the signal from one steering sensor does not closely match the signal from one of the other steering sensors.
If one ECM has activated an FMI 14 diagnostic code and the other ECM has not, the sensor is probably operating correctly. When this condition occurs, a poor connection in the machine harness would be suspected.
When both ECM modules have activated the diagnostic code, either the sensor or a harness problem could be the cause.
If both ECM modules have activated the diagnostic code, either ECM is unlikely to be the cause of the problem.
For either condition, proceed with this procedure in order to verify the cause of the problem.

Note: When checking the diagnostic information using Cat ET, confirm that the latest version of the ET software is installed on the laptop.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the problem has been corrected.

Note: The next three test steps will measure the duty cycle of each steering sensor. The measurement of the duty cycle will determine if one signal is not closely matching with both of the other sensor signals. Record the duty cycle of the sensor signal for each of the three sensors for comparison.




Illustration 2g03610438

ECM (Joystick) PWM Sensors

Note: The diagram above is simplified schematic of the Transmission ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR3921 for the complete schematic.

Implement 2 (Steering) ECM

The following is a list of diagnostic codes that are associated with the PWM Sensors of the machine.

Table 2
Implement ECM 2 (Steering) (MID 145)    
DTC     Code Description     System Response    
1471-2     Steering Control Position Sensor #1: Data Erratic, Intermittent, or Incorrect     A Warning Level 3 Will Be Generated.    
1471-3     Steering Control Position Sensor #1: Voltage Above Normal     A Warning Level 3 Will Be Generated.    
1471-4     Steering Control Position Sensor #1: Voltage Below Normal     A Warning Level 3 Will Be Generated.    
1471-8     Steering Control Position Sensor #1: Abnormal Frequency, Pulse Width, or Period     A Warning Level 3 Will Be Generated.    
1471-14     Steering Control Position Sensor #1: Special Instruction     A Warning Level 3 Will Be Generated.    
1472-2     Steering Control Position Sensor #2: Data Erratic, Intermittent, or Incorrect     A Warning Level 3 Will Be Generated.    
1472-3     Steering Control Position Sensor #2: Voltage Above Normal     A Warning Level 3 Will Be Generated.    
1472-4     Steering Control Position Sensor #2: Voltage Below Normal     A Warning Level 3 Will Be Generated.    
1472-8     Steering Control Position Sensor #2: Abnormal Frequency, Pulse Width, or Period     A Warning Level 3 Will Be Generated.    
1472-14     Steering Control Position Sensor #2: Special Instruction     A Warning Level 3 Will Be Generated.    
1473-2     Steering Control Position Sensor #3: Data Erratic, Intermittent, or Incorrect     A Warning Level 3 Will Be Generated.    
1473-3     Steering Control Position Sensor #3: Voltage Above Normal     A Warning Level 3 Will Be Generated.    
1473-4     Steering Control Position Sensor #3: Voltage Below Normal     A Warning Level 3 Will Be Generated.    
1473-8     Steering Control Position Sensor #3: Abnormal Frequency, Pulse Width, or Period     A Warning Level 3 Will Be Generated.    
1473-14     Steering Control Position Sensor #3: Special Instruction     A Warning Level 3 Will Be Generated.    

Pulse Width Modulation (PWM) is a technique for controlling analog circuits with digital outputs. PWM is employed in various applications ranging from measurement to communication with the Electronic Control Module (ECM). The duty cycle of a square wave is modulated to encode a specific analog signal level. The duty cycle is the ratio of the on-time to the period. The modulating frequency is the inverse of the period. The duty cycle is programmed into the software of the ECU. The engineer (or programmer) sets the period in the on-chip timer counter that provides the modulating square wave. The engineer sets the direction of the PWM output along with the on-time in the PWM control register.

One of the advantages of the PWM sensor is that the signal remains digital all the way from the ECM to the controlled system. No digital to analog conversion is necessary. By using a digital signal, noise effects are minimized. Noise affects a digital signal if the noise can change a logic 1 to a logic 0 or a logic 0 to a logic 1.

Possible Causes for an FMI 2 Diagnostic code are:

  • The sensor has failed.

  • An Intermittent connection exists in the sensor circuit.

  • The signal circuit is shorted to another circuit in the machine harness.

  • The sensor has failed.

  • The ECM has failed. ECM failure is unlikely.

Consider the following points when this code is active:

  • Use Cat ET to determine if an MID 145 CID 41 diagnostic code is active. If the diagnostic code for the 8 VDC power supply is active, fix the problem before proceeding.

  • The Transmission/Chassis ECM (MID 27) and the Implement ECM 2 (MID 145) receive an input signal from the "Steering Sensor 1". Both ECM modules can activate an FMI 2 diagnostic code when the signal is erratic or intermittent.

  • When only one of the ECM modules has an active FMI 2 diagnostic code, the probability is that the sensor is operating correctly. When this condition occurs, a poor connection in the machine harness would be suspected.

  • When both ECM modules have activated the diagnostic code, either the sensor or a harness problem may be the cause.

  • If both ECM modules have activated the diagnostic code, either ECM is probably not the cause the problem.

  • For either condition, proceed with this procedure to verify the cause of the problem.


Possible Causes for an FMI 3 Diagnostic code are:

  • The sensor supply or the ground circuit in the machine harness is open.

  • The signal circuit in the machine harness is shorted to the +battery.

  • The signal circuit in the machine harness is open or the sensor is disconnected.

  • The sensor has failed.

  • The Transmission ECM has failed. A failure of the ECM is unlikely.

Possible Causes for an FMI 4 Diagnostic code are:

  • The sensor has failed.

  • The signal circuit in the machine harness is shorted to ground.

  • The Transmission ECM has failed. A failure of the ECM is unlikely

Possible Causes for an FMI 8 Diagnostic code are:

  • The sensor has failed

  • Intermittent connections or poor connections

  • The spacing of the sensor is incorrect

  • Mechanical devices are loose

  • Incorrect software is loaded to the ECM

  • The ECM has failed. ECM failure is unlikely

Possible Causes for an FMI 14 Diagnostic code are:

  • The sensor has failed.

  • The ECM has failed. A failure of the Transmission/Chassis ECM is unlikely.

Three steering position sensors are required for correct operation of the steering control. The steering position sensors are located in the left joystick assembly. Each sensor provides an input signal to the Implement ECM 2 and to the "Transmission/Chassis ECM". The ECM expects the input signals from all three steering position sensors to match closely. The FMI 14 diagnostic indicates that the sensor input signal does not match the other two sensors. The Transmission/Chassis ECM determines the status of the input signals from the three steering sensors. The code is active when "Steering Sensors" do not match another sensor but still matches the third sensor.

The "Steering Position Sensors" receive power from the 8 VDC power supply of the Implement ECM 2. The "Steering Position Sensors" are internally connected to the ground at both ECM modules. The steering sensor must lose both grounds in order to lose a ground connection. The illustration above indicates the power and ground connections for the "Steer Sensors".

The position sensor is a PWM sensor that operates at a frequency of approximately 500 ± 80 Hz. The position sensor sends a PWM input signal to the Implement ECM 2 and to the "Transmission/Chassis ECM". The duty cycle will vary from 10% at the lever full left position to 90% at the lever full right position. When the lever is in the center position, the duty cycle will be approximately 50%.

Note: If an MID 082 CID 41 diagnostic code is active, fix the problem before proceeding with this procedure.

Note: The correct operating temperature range for the steering sensors is −40 °C (−40.0 °F) to 75 °C (167.0 °F). Return the temperature in the cab to normal when the cab temperature is extreme resulting in an FMI 03 or FMI 08 diagnostic code. An FMI 14 diagnostic code is also possible in these circumstances. Returning the temperature in the cab to a normal temperature will keep the steering position sensors operating in the acceptable temperature range. After stabilization of the temperature, verify that the FMI 14 diagnostic code is active before performing this procedure.

Note: The "Transmission/Chassis ECM" (MID 027) and the Implement ECM 2 (MID 082) receive an input signal from the "Steering Sensors". Both ECM modules can activate an FMI 14 diagnostic code. The code is activated when the signal from one steering sensor does not closely match the signal from one of the other steering sensors.
If one ECM has activated an FMI 14 diagnostic code and the other ECM has not, the sensor is probably operating correctly. When this condition occurs, a poor connection in the machine harness would be suspected.
When both ECM modules have activated the diagnostic code, either the sensor or a harness problem could be the cause.
If both ECM modules have activated the diagnostic code, either ECM is unlikely to be the cause of the problem.
For either condition, proceed with this procedure in order to verify the cause of the problem.

Note: When checking the diagnostic information using Cat ET, confirm that the latest version of the ET software is installed on the laptop.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the problem has been corrected.

Note: The next three test steps will measure the duty cycle of each steering sensor. The measurement of the duty cycle will determine if one signal is not closely matching with both of the other sensor signals. Record the duty cycle of the sensor signal for each of the three sensors for comparison.




Illustration 3g03610438

ECM (Joystick) PWM Sensors

Note: The diagram above is simplified schematic of the ECM connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR3921 for the complete schematic.

Diagnostic Trouble Code Procedure

Note: Prior to beginning this procedure, inspect the harness connectors that are involved in this circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. Check the wiring for pinch points or abrasions. Look for and repair areas that indicate wires are exposed. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing a troubleshooting procedure.

Table 3
Troubleshooting Test Steps     Values     Results    
1. Identify Active FMI Code Associated With Sensor Circuit    
Code present    
FMI 2 diagnostic code, proceed to Test Step 2.

FMI 3 diagnostic code, proceed to Test Step 5.

FMI 4 diagnostic code, proceed to Test Step 11.

FMI 8 diagnostic code, proceed to Test Step 13.

FMI 14 diagnostic code, proceed to Test Step 16.    
Begin Process For FMI 2 Troubleshooting HERE    
2. CHECK THE POWER SUPPLY CIRCUIT OF THE SENSOR

A. Turn key start switch and disconnect switch ON.

B. Do not disconnect the sensor from the machine harness J1 connector.

D. At the J1 harness connector for the left joystick, insert multimeter probes along the contact of the power supply wire and along ground 3 contact wire.

E. Measure the DC voltage.

F. At the harness connectors for the left joystick, perform the following:
a. Remove the multimeter probe that is inserted along the ground 3 contact J1-8 and insert the probe along ground 2 contact J1-4 (wire X800-OR).
b. The other probe remains inserted along the contact of the power supply J1-1 (wire R800-OR).

Measure the DC voltage.    

The voltage measurement is approximately 8.0 VDC    
OK - The voltage reading is correct for the suspected faulty sensor.

Proceed to Test Step 3.

NOT OK- The voltage is NOT correct for the circuit.

Repair - If Both voltage measurements are not correct, the problem is most likely in the power circuit of the wire. This condition will cause multiple diagnostic codes to activate.
Refer to the Electrical Schematic of the machine. Examine all of the connectors that are in the power and ground circuits. Inspect the connections for the following:
a. Connections are clean.
b. Connections are secure.
c. Connections are in good condition.

For troubleshooting the ECM power supply that is providing power to the sensor, refer to the CID 41 diagnostic code procedures in the Troubleshooting Section of the manual.

STOP

NOT OK- The voltage is NOT correct for the circuit.

Repair - If one of the voltage measurements is correct and the other is not, there is a problem in the ground circuit which registered the bad measurement. This condition will not cause this diagnostic code to activate. There is another problem that causes this diagnostic code to activate. However, the ground circuit must be repaired before proceeding with this procedure
Do not operate the machine with only one ground connection for the left joystick.
Repair the faulty ground circuit before proceeding with this procedure.

Proceed to Test Step 3.    
3. Check The Signal At The Sensor

A. The key start switch and the disconnect switch remain in the OFF position.

B. The machine harness connector J1 remains connected to the connector of the left joystick.

C. At the machine harness connector J1 for the left joystick, use a 151-6320 Removal Tool to remove the following from the harness connector:
The signal wire U739-BR and socket at contact J1-2

D. At the back of the joystick of the connector J1, insert multimeter probes along the sensor signal contact J1-2 and the ground contact at J1-4.

E. Turn the disconnect switch to the ON position

F. Turn the key start switch to the ON position

Measure the duty cycle of the sensor at the contacts of the joystick of the connector J1-2 and J1-4.

H. Move the joystick through the full range of the sensor that is described at the beginning of this procedure.    

The duty cycle of the number one sensor is correct according to the description at the beginning of this procedure.    
OK - The duty cycle of the sensor is correct. The sensor is not the cause of the problem.
Reinstall the signal wire and the socket back to the original location at contact J1-2 in the machine harness connector for the joystick. Verify that all the wires of the joystick are in the correct locations. Also, ensure the wires that are secured in the connector before proceeding to the next step.

Proceed to test step 4

NOT OK - The duty cycle of the number one sensor is not correct according to the description at the beginning of this procedure. The sensor has failed.

Repair - Perform this test step again to verify that the sensor signal is not correct.
If the signal of the number one sensor is not correct, see the description at the beginning of this procedure. Replace the joystick faceplate. Refer to Special Instruction REHS7448Procedure To Remove And Replace The Left-Hand Joystick Push-Button Faceplate on M Series, M Series 2, and M Series 3 Motor Graders After replacement of the assembly of the joystick, verify that the operation of the new assembly of the joystick is correct before operating the machine.

STOP    
4. Check The Signal At Both Electronic Control Modules

A. Turn the disconnect switch to the OFF position.

B. Turn the key start switch to the OFF position.

C. The machine harness connectors remain connected to the ECM.

D. At the machine harness connector J1 for the Transmission/Chassis ECM, insert a multimeter probe along return contact J1-45 (wire X800-OR).

E. At the machine harness connector J2 for the Transmission/Chassis ECM, insert a multimeter probe along signal contact J2-18 (wire U739-BR).

F. Turn the disconnect switch to the ON position.

G. Turn the key start switch to the ON position.

H. Measure the duty cycle of the sensor at the contacts of the ECM connector J1-45 and J2-18.

I. Move the joystick through the full range of the sensor that is described at the beginning of this procedure.

J. The machine harness connectors remain connected to the ECM.

K. At the machine harness connector J1 for the Implement ECM 2, insert a multimeter probe along return contact J1-45 (wire P967-PU).

L. At the machine harness connector J2 for the Implement ECM 2, insert a multimeter probe along signal contact J2-32 (wire U739-BR).

M. Measure the duty cycle of the sensor at the contacts of the ECM connector J1-45 and J2-32.

N. Move the joystick through the full range of the sensor that is described at the beginning of this procedure.    

The duty cycle of the # 1 sensor is correct according to the description at the beginning of this procedure at both of the ECMs.    
OK - The duty cycle of the sensor is correct at both of the electronic control modules. The machine harness does not appear to be the cause of the problem. An intermittent open or a short could still be causing the problem.

Proceed to Test Step 5

NOT OK - The duty cycle of the sensor is not correct at one of the ECMs according to the description at the beginning of this procedure. There is a problem in the machine harness.

Repair - If the sensor signal at one ECM is correct the other ECM is not, a poor connection in the circuit is suspected.
The signal for the number one sensor at one of the electronic control modules is not correct.
Refer to the Electrical Schematic of the machine. Examine all connectors in the section of the sensor signal circuit that connects to the ECM not receiving a good signal. Inspect the connections for the following:
a. Connections are clean.
b. Connections are secure.
c. Connections are in good condition.
Repair or replace the machine harness.
STOP

NOT OK - The duty cycle of the sensor is not correct at either of the ECMs according to the description at the beginning of this procedure. There is a problem in the machine harness.

Proceed to test step 5.    
5. Check The Signal Circuit For A Short

A. Turn the disconnect switch to the OFF position.

B. Turn the key start switch to the OFF position.
C. Disconnect the harness connector J1 and J2 from the Implement ECM 2.

D. At the J2 machine harness connector for the Implement ECM 2, measure the resistance from the sensor signal contact J2-32 (wire U739-BR) to all of the other J1 and J2 contacts that are used for the Implement ECM 2.

E. If any of the resistance measurements in the last test step are less than 5k Ω, skip the next test step and proceed to the step of "Expected Result". If all of the resistance measurements in the last test step are above 5k Ω, perform the next test step.

F. Disconnect the harness connector J1 and J2 from the Transmission/Chassis ECM.

G. At the J2 machine harness connector for the Transmission/Chassis ECM, measure the resistance from the sensor signal contact J2-18 (wire U739-BR) to all of the other J1 and J2 contacts that are used for the Transmission/Chassis ECM.
   

Resistance greater than 5k Ω for all readings.    
OK - Each resistance is greater than 5k Ω. The signal circuit of the resistance is not indicating a short in the machine harness.

Proceed to Test Step 17.

NOT OK- A resistance is less than 5k Ω.

Repair - There is a short in the machine harness. The short is between the signal circuit and the circuit with the low resistance measurement.

Refer to the Electrical Schematic of the machine. Check all of the connectors that are in the sensor circuit. Inspect the connections for the following:
Connections are clean.
Connections are secure.
Connections are in good condition.

For information on testing for short circuits and finding short circuits, refer to the Troubleshooting, "Wiring Harness (Short Circuit) - Test" Story in this manual. Repair the machine harness or replace the machine harness.

STOP    
Begin Process For FMI 3 Troubleshooting HERE    
6. Check The Supply Voltage At The Sensor

Use a calibrated digital multimeter for the measurements in this procedure

A. Turn key start switch and disconnect switch ON.

B. At the J1 harness connector for the left joystick, insert 7X-1710 Multimeter Probes along the contact of the power supply J1-1 (wire R800-OR) and along the ground 1 contact J1-8 (wire P967-PU). Do not disconnect the machine harness from the J1 connector.

C. Measure the DC voltage.

D. At the harness connectors for the left joystick, remove the multimeter probe that is inserted along contact J1-8 and insert the probe along ground 2 contact J1-4 (wire X800-OR). The other probe remains inserted along the contact of the power supply J1-1 (wire R800-OR).

E. Measure the DC voltage.    

The voltage measurement is approximately 8.0 VDC    
OK - The voltage reading is correct for the suspected faulty sensor.

Proceed to Test Step 7.

NOT OK- The voltage is NOT correct for the circuit.

Repair - If both of the voltage measurements are not correct, the problem is most likely in the power circuit. Multiple diagnostic codes will be activated along with this diagnostic code. Refer to the complete Electrical System Schematic of the machine. Examine all of the connectors that are in the power and ground circuits. Ensure that the connections are clean, that all connections are secure and that all connections are in good condition. Repair or replace the machine harness.
To troubleshoot the ECM power supply, refer to the CID 41 diagnostic code procedure. The troubleshooting procedure is located in the manual for the "Implement ECM 2".

STOP

NOT OK - One of the voltage measurements is not correct.
Repair - If only one of the voltage measurements is correct, there is a problem in the ground circuit that registered the bad measurement. This condition will not cause this diagnostic code to activate. There is another problem that is caused by this active diagnostic code, however, the ground circuit must be repaired before proceeding with this procedure.
Do not operate the machine with only one ground connection for the left joystick.
Repair the faulty ground circuit or the circuit for the power supply before proceeding with this procedure.

Proceed to test step 7.    
7. Check The Operation Of The Sensor For The Joystick

The key start switch and the disconnect switch remain in the OFF position.

A. Reconnect the machine harness connectors J1 and J2 to both ECM modules.

B.Reconnect the machine harness connectors that are disconnected to the left joystick.

C. At the machine harness connector J1 for the left joystick, use a 151-6320 Removal Tool to remove the signal wire U739-BR and the socket at contact J1-2 from the harness connector. The machine harness connector J1 remains connected to the connector of the left joystick.

D. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along contact J1-2 and contact J1-4.

E. Turn the disconnect switch and the key start switch to the ON position.

F. Measure the duty cycle of the sensor at the connector of the joystick, contacts J1-2, and J1-4. Move the joystick through the full range of the sensor that is described at the beginning of this procedure.    

The duty cycle of the Steering Sensor is correct according to the description at the beginning of this procedure.    
OK - The duty cycle of the sensor is correct. The sensor is not the cause of the problem.

Reinstall the signal wire U739-BR and the socket back to the original location at contact J1-2 in the machine harness connector for the joystick. Verify that all of the wires of the joystick are in the correct locations. Confirm that all wires are secure in the connector before proceeding to the next step.

Proceed to Test Step 8.

NOT OK - The duty cycle of the affected "Steering Sensor" is not correct according to the description at the beginning of this procedure. The sensor has failed.

Repair:Perform this test step again in order to verify that the sensor signal is not correct.
If the signal of the sensor is not correct (see the description at the beginning of this procedure), replace the joystick faceplate. Refer to Special Instruction REHS7448Procedure To Remove And Replace The Left-Hand Joystick Push-Button Faceplate on M Series, M Series 2, and M Series 3 Motor Graders After replacement of the assembly of the joystick, verify that the operation of the new assembly of the joystick is correct before operating the machine.

STOP    
8. Check The Signal At Both ECM Modules

A. Turn the key start switch and the disconnect switch to the OFF position.

B. At the machine harness connector J1 for the "Transmission/Chassis ECM", insert a multimeter probe along return contact J1-45 (wire X800-OR). At the machine harness connector J2 for the "Transmission/Chassis ECM", insert a multimeter probe along signal contact J2-18 (wire U739-BR). The machine harness connectors remain connected to the ECM.

C. Turn the key start switch and the disconnect switch to the ON position.

D. Measure the duty cycle of the sensor at the contacts of the ECM J1-45 and J2-18. Move the joystick through the full range of the sensor that is described at the beginning of this procedure.

E. At the machine harness connector J1 for the Implement ECM 2, insert a multimeter probe along return contact J1-45 (wire P967-PU). At the machine harness connector J2 for the Implement ECM 2, insert a multimeter probe along signal contact J2-18 (wire U739-BR). The machine harness connectors remain connected to the ECM.

F. Measure the duty cycle of the sensor at the connector contacts of the ECM J1-45 and J2-18. Move the joystick through the full range of the sensor that is described at the beginning of this procedure.    

The duty cycle of the sensor is correct according to the description at the beginning of this procedure.    
OK- The duty cycle of the sensor is correct at both of the ECM modules. The machine harness does not appear to be the cause of the problem. An intermittent open or a short could still be the cause of the problem.

Proceed to Test Step 9.

NOT OK- The duty cycle of the sensor is NOT correct at one of the ECMs according to the description at the beginning of this procedure. There is a problem in the machine harness.

Repair: If the sensor signal at only one ECM is correct, a poor connection in the circuit would be suspected.
The affected "steering sensor" signal at one of the ECM modules is not correct.
Refer to the complete Electrical System Schematic of the machine. Examine all of the connectors that are in the signal circuit that connects to the ECM. Verify that the connections are clean, that the connections are secure and that the connections are in good condition. Repair the machine harness or replace the machine harness.

STOP    
9. Check For an Open In The Sensor Circuits Of Both ECM Modules

A. Turn the key start switch and the disconnect switch to the OFF position.

B. Disconnect the machine harness connector J1 from the left joystick. At harness connector J1 for the joystick, place a jumper wire between the ground 2 contact J1-4 (wire X800-OR) and the signal contact J1-2 (wire U739-BR).

C. Disconnect machine harness connectors J1 and J2 from the "Transmission/Chassis ECM".
D. At the harness connector for the "Transmission/Chassis ECM", measure the resistance from ground at contact J1-45 (wire X800-OR) to the signal contact J2-18 (wire U739-BR).

E. Observe the resistance measurement and wiggle the ECM connector and the sensor connector. Gently pull on the wires and wiggle the wires for both connectors.

F. At harness connector J1 for the joystick, move the jumper wire to the ground 1 contact J1-8 (wire P967-PU) and the signal contact J1-2 (wire U739-BR) .

G. Disconnect machine harness connectors J1 and J2 from the Implement ECM 2.

H. At the harness connectors for the Implement ECM 2, measure the resistance from ground 1 return contact J1-45 (wire P967-PU) to signal contact J2-18 (wire U739-BR).

I. Observe the resistance measurement and wiggle the ECM connector and the sensor connector. Gently pull on the wires and wiggle the wires for both connectors.    

Resistance less 5k Ω at all times during the manipulation of the wiring harness and connectors.    
OK- Both of the resistance measurements are less than 5k Ω. The sensor circuit is not open in either of the input circuits of the ECM modules.

Proceed to Test Step 10.

NOT OK- The resistance greater than 5k Ω. There is an open or a bad connection in one or both of the signal circuits.

Repair: If both of the resistance measurements are not correct, there is a bad connection on the sensor side of the splice at the signal wire U739-BR.
In either case, refer to the complete Electrical System Schematic of the machine. Check all of the connectors that are in the suspected section of the sensor signal circuit. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition. Repair the machine harness or replace the machine harness.

STOP    
10. Check The Signal Circuit For A Short

The key start switch and the disconnect switch remain in the OFF position. The machine harness connectors remain disconnected from the Implement ECM 2 and the "Transmission/Chassis ECM".

A. Remove the jumper wire that was installed in the last step at the connector of the joystick.

B. At the J2 machine harness connector for the Implement ECM 2, measure the resistance from the sensor signal contact J2-18 (wire U739-BR) to all of the other J1 and J2 contacts that are used for the Implement ECM 2.

C. If any of the resistance measurements in the last test step are less than 5k Ω, skip the next test step and proceed to the "Expected Result" step. If all of the resistance measurements in the last test step are above 5k Ω, perform the next test step.

D. At the J2 machine harness connector for the "Transmission/Chassis ECM", measure the resistance from the sensor signal contact J2-18 (wire U739-BR) to all of the other J1 and J2 contacts that are used for the Transmission/Chassis ECM.    

Resistance greater than 5k Ω for all readings.    
OK - Each resistance measurement is greater than 5k Ω. The resistance checks of the signal circuit do not indicate a short in the machine harness.

Proceed to test step 11.

NOT OK - A resistance is less than 5k Ω.

Repair - There is a short in the machine harness. The short is between the signal circuit and the circuit with the low resistance measurement.
Refer to the complete Electrical System Schematic of the machine. Check all of the connectors that are in the sensor circuit. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition.
For information on testing for short circuits and finding short circuits, refer to Troubleshooting, "Wiring Harness (Short Circuit) - Test". Repair the machine harness or replace the machine harness.

STOP    
11. Check The Operation Of The ECM

The disconnect switch and the key start switch remain in the OFF position.

A. Reconnect the J1and J2 machine harness connectors to the Implement ECM 2 and to the "Transmission/Chassis ECM".

B. At the machine harness connector J2 for the "Transmission/Chassis ECM", use a 151-6320 Removal Tool to remove the request signal wire U740-BU and the socket at contact J2-48 from the harness connector. The machine harness connector J2 remains connected to the ECM.

C. Turn the disconnect switch and the key start switch to the ON position.

D. Use a 7X-1710 Multimeter Probe not connected to a multimeter to contact the pin of the "Transmission/Chassis ECM" at J2-48 through the empty space in the J2 connector.

E. Observe the status of the active FMI 03 diagnostic code and ground the other end of the 7X-1710 Multimeter Probe to frame ground.    

The FMI 03 diagnostic code is no longer active. An FMI 04 diagnostic code becomes active when the ECM pin at J2-48 is grounded.    
OK - The FMI 03 diagnostic code is no longer active. An FMI 04 diagnostic code has been activated after the ECM pin is grounded. The ECM has responded correctly to the grounded circuit condition. The ECM is an unlikely cause of the problem.

Reconnect the wire into the correct spot of the ECM connector before proceeding to the next step.

Proceed to test step 15.

NOT OK - The 03 diagnostic code remains active. The status of the active diagnostic code does not change when the ECM pin is grounded.

Repair -
Prior to replacing an ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM must be replaced, refer to Troubleshooting, "(ECM) - Replace".

STOP    
Begin Process For FMI 4 Troubleshooting HERE    
12. Check The Sensor

A. Turn the disconnect switch and the key start switch to the ON position.

B. Disconnect the machine harness connector J1 from the left joystick. Observe the status of the active FMI 4 diagnostic code.    

The status of the FMI 4 diagnostic code did not change when the connector of the joystick was disconnected. An FMI 3 diagnostic code has NOT been activated by either the "Implement ECM 2" or the "Transmission/Chassis ECM". The FMI 4 diagnostic code remains active when the connector of the joystick is disconnected.    
OK - The diagnostic changed to FMI 3 when the sensor was disconnected.

Repair: Replace the sensor.

STOP

NOT OK - The FMI 4 diagnostic code remains active when sensor is disconnected. The sensor is not the cause of the problem.

Proceed to Test Step 13.    
13. Check The Signal Circuit For A Short To Ground

A. Turn the key start switch and the disconnect switch OFF.

B. The sensor remains disconnected from the harness
C. Disconnect the J1 and J2 machine harness connectors from the Implement ECM 2.

D. Disconnect the J1 connector and the J2 connector from the "Transmission/Chassis ECM".

E. At machine harness connector J2 for the Implement ECM 2, measure the resistance from contact J2-18 (wire U739-BR) to frame ground. Measure the resistance from contact J2-18 (wire U739-BR) to all of the other J1 and J2 contacts that are used for the Implement ECM 2.

F. At the J2 machine harness connector for the "Transmission/Chassis ECM", measure the resistance from the sensor signal contact J2-18 (wire U739-BR) to all of the other J1 and J2 contacts that are used for the "Transmission/Chassis ECM".    

The resistance is greater than 5k Ω.    
OK - The resistance is greater than 5k Ω. The harness circuit is correct.

Proceed to Test Step 17.

NOT OK - The resistance is less than 5 Ω. A short circuit exists between frame ground and the signal circuit.

Repair: There is a short in the machine harness. The short is between the circuit for the signal and the frame ground or the circuit with the low resistance measurement.
Refer to the complete Electrical System Schematic of the machine. Check all of the connectors that are in the sensor circuit. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition.
For information on testing for short circuits and finding short circuits, refer to Troubleshooting, "Wiring Harness (Short Circuit) - Test". Repair the machine harness or replace the machine harness.

Note: A resistance greater than 5 Ω but less than 5k Ω would indicate a loose or corroded connection in the circuit. A resistance measurement that is greater than 5k Ω would indicate an open in the circuit.

STOP    
Begin Process For FMI 8 Troubleshooting HERE    
14. Check The Duty Cycle And The Signal Frequency At The Sensor

Turn the key start switch and the disconnect switch to the OFF position.

A. At the machine harness connector J1 for the left joystick, use a 151-6320 Removal Tool to remove the signal wire (wire U739-BR) and the socket at contact J1-2. The machine harness connector J1 remains connected to the left connector of the joystick.

B. At the back of the connector of the joystick J1, insert 7X-1710 Multimeter Probes along contact J1-2 and contact J1-4.

C. Turn the disconnect switch and the key start switch to the ON position.

D. With the joystick in a stationary position, measure the frequency of the signal from the sensor.

E. Observe the measurement of the resistance and wiggle the connector of the joystick. Gently pull on the wires and wiggle the wires.
F. Observe the measurement and wiggle the sensor connector. Gently pull on the wires and wiggle the wires
G. Observe the measurement of the resistance and wiggle the connector of the joystick. Gently pull on the wires and wiggle the wires.    

The frequency and duty cycle of the signal is correct according to the description at the beginning of this procedure. The frequency and the duty cycle are stable during the manipulation of the harness connector and the wiring    
OK - The frequency of the sensor and the duty cycle of the sensor are correct and did not change as the harness was manipulated. The sensor is not the cause of the problem.
Reconnect the signal wire and the socket in the machine harness connector for the joystick. Verify that all wires of the joystick are secure in the connector before proceeding to the next step.

Proceed to Test Step 15.

NOT OK- The signal frequency or the duty cycle of the sensor is not correct according to the description at the beginning of this procedure. The sensor has failed

Repair - Perform this test step again in order to verify that the sensor signal is not correct.
If the signal of sensor is not correct according to the description at the beginning of this procedure, replace the joystick faceplate. Refer to Special Instruction REHS7448Procedure To Remove And Replace The Left-Hand Joystick Push-Button Faceplate on M Series, M Series 2, and M Series 3 Motor Graders After replacement of the assembly of the joystick, verify that the operation of the new assembly of the joystick is correct before operating the machine.

STOP    
15. Check For An Open In The Sensor Circuit At Both Of The ECM Modules

A. Turn the key start switch and the disconnect switch to the OFF position.

B. Disconnect the machine harness connector J1 from the left joystick. At harness connector J1 for the joystick, place a jumper wire between the ground 2 contact J1-4 (wire X800-OR) and the signal contact J1-2 (wire U739-BR) .

C. Disconnect machine harness connectors J1 and J2 from the "Transmission/Chassis ECM".

Note: Ensure that the frame ground contact point is clean and free of paint, oil, dirt, and any other debris

D. At the harness connector for the "Transmission/Chassis ECM", measure the resistance from ground 2 return contact J1-45 (wire X800-OR) to signal contact J2-18 (wire U739-BR).

E. Observe the resistance measurement and wiggle the ECM connector and the sensor connector. Gently pull on the wires and wiggle the wires for both connectors.

F. At harness connector J1 for the joystick, move the jumper wire to the ground 1 contact J1-8 (wire P967-PU) and the signal contact J1-2 (wire U739-BR).

G. Disconnect machine harness connectors J1 and J2 from the "Implement ECM 2".

H. At the harness connectors for the "Implement ECM 2", measure the resistance from contact J1-45 (wire P967-PU) to contact J2-18 (wire U739-BR).

I. Observe the resistance measurement and wiggle the ECM connector and the sensor connector. Gently pull on the wires and wiggle the wires for both connectors.    

Both resistance measurements are less than 5k Ω at all times during the manipulation of the wiring harness and connectors.    
OK - Both of the resistance measurements are less than 5k Ω. The sensor circuit is not open in the input circuit of either of the ECM modules.

Proceed to Test Step 17.

NOT OK -The resistance measurement at one or both of the ECM modules is greater than 5 Ω. There is an open or a bad connection in one or both of the signal circuits.

Repair - If both of the resistance measurements are not correct, a bad connection on the sensor side of the splice for the signal wire U739-BR.
If only one of the measurements is correct, there is an open or a bad connection on the ECM side of the splice for wire U739-BR.
In either case, refer to the complete Electrical System Schematic of the machine. Check all of the connectors that are in the suspected section of the signal circuit of the sensor. Ensure that all connections are clean, that all connections are secure and that all connections are in good condition. Repair the machine harness or replace the machine harness.

STOP    
Begin Process For FMI 14 Troubleshooting HERE    
16. Check The Signal At The Affected "Steer Sensor"

A. Turn the key start switch and the disconnect switch to the OFF position.

B. Do not disconnect the harness connector from the sensor.

C. At the back of the joystick connector J1, insert 7X-1710 Multimeter Probes along the sensor signal contact J1-2 and the return contact at J1-4

D. Turn the disconnect switch and the key start switch to the ON position.

E. Monitor the signal of the sensor with a digital multimeter.

F. Move the joystick through the full range of operation. Record the duty cycle of the sensor at specific positions of the joystick.

G. Repeat the process for the other two steer position sensors.    

The duty cycle of the three steering sensors is within 5% of each other.    
OK - The duty cycle has been recorded for comparison with the other two steering sensors. With the joystick at the same position for all three readings, the duty cycle readings are within 5% of each other. Reconnect the signal wire in the machine harness connector for the joystick before proceeding to the next test step.

Go to test step 17.

NOT OK - The joystick was maintained in the same position for reading the duty cycle of the three sensors. One or more of the readings varies by more than 5% from the other duty cycle readings. One or more of the steering sensors are not working properly.

Repair: Replace the joystick faceplate. Refer to Special Instruction REHS7448Procedure To Remove And Replace The Left-Hand Joystick Push-Button Faceplate on M Series, M Series 2, and M Series 3 Motor Graders After replacement of the assembly of the joystick, verify that the operation of the new assembly of the joystick is correct before operating the machine.
Clear all logged codes prior to confirming the function of the new assembly.

STOP    
17. Check The Status Of The Diagnostic Code

A. Inspect the harness connectors. Clean the contacts of the harness connectors. Check the wires for damage to the insulation that is caused by excessive heat, battery acid, or chafing.

B. Perform a
45 N (10 lb) pull test on each of the wires that are associated with the sensor circuit.

C. Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are fastened securely.

D. Turn the disconnect switch and the key start switch to the ON position.

E. Operate the machine.

F. Determine if the diagnostic code is active.    

The diagnostic code is not active.    
OK - The diagnostic code is not active. The diagnostic code does not exist at this time. The initial diagnostic code was probably caused by a poor connection or a short at one of the connectors that was disconnected and reconnected. Resume normal operation.

STOP

NOT OK - The diagnostic code is active. The diagnostic code has not been corrected.

Repair - Check the circuit again. Use the Caterpillar Electronic Technician (ET) service tool, if available, in order to perform a wiggle test on the machine wiring harness. The wiggle test can detect momentary or intermittent shorts or opens in the machine wiring harness.
If the cause of the active diagnostic code is not found, the ECM that has activated this diagnostic code may have failed.
If both the "Transmission/Chassis ECM" and the Implement ECM 2 have activated this diagnostic code, either ECM as the cause of the problem is unlikely.
Exit this procedure and perform this procedure again. If the cause of the failure is not found, contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time.
If the ECM must be replaced, refer to Troubleshooting, "(ECM) - Replace".

STOP    

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