Sensor Signal (PWM) - Test
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 ECM. 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.
The following is a list of diagnostic codes that are associated with the PWM sensors for the Transmission ECM.
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| Transmission ECM (MID 81) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 96-3 | Fuel Level Sensor: Voltage Above Normal | The Transmission ECM compares the machine supply voltage, 5 VDC component voltage, and the supply voltage for the specific sensor before issuing a fault.
If the voltage for the sensor circuit is above normal, the fault code is displayed. The fuel level will not be displayed accurately. |
| 96-4 | Fuel Level Sensor: Voltage Below Normal | The Transmission ECM compares the machine supply voltage, 5 VDC component voltage, and the supply voltage for the specific sensor before issuing a fault.
If the voltage for the sensor circuit is below normal, the fault code is displayed. The fuel level will not be displayed accurately. |
| 96-8 | Fuel Level Sensor: Abnormal Frequency, Pulse Width, or Period | |
| 427-3 | Front Axle Oil Temperature Sensor: Voltage Above Normal | The Transmission ECM compares the machine supply voltage, 5 VDC component voltage, and the supply voltage for the specific sensor before issuing a fault.
If the voltage for the sensor circuit is above normal, the fault code is displayed. The temperature for the oil is inaccurate. |
| 427-4 | Front Axle Oil Temperature Sensor: Voltage Below Normal | The Transmission ECM compares the machine supply voltage, 5 VDC component voltage, and the supply voltage for the specific sensor before issuing a fault.
If the voltage for the sensor circuit is below normal, the fault code is displayed. The temperature for the oil is inaccurate. |
| 427-8 | Front Axle Oil Temperature Sensor: Abnormal Frequency, Pulse Width, or Period | The sensor is a PWM sensor that operates at a frequency of approximately 500 ± 200 Hz. The sensor sends a PWM input signal to the ECM.
If the PWM frequency is outside the 500Hz ± 200 Hz operating range, the diagnostic code will be activated. This code results from a failure of the sensor or an intermittent circuit connection. The temperature for the oil is inaccurate. |
| 428-3 | Rear Axle Oil Temperature Sensor: Voltage Above Normal | The Transmission ECM compares the machine supply voltage, 5 VDC component voltage, and the supply voltage for the specific sensor before issuing a fault.
If the voltage for the sensor circuit is above normal, the fault code is displayed. The temperature for the oil is inaccurate. |
| 428-4 | Rear Axle Oil Temperature Sensor: Voltage Below Normal | The Transmission ECM compares the machine supply voltage, 5 VDC component voltage, and the supply voltage for the specific sensor before issuing a fault.
If the voltage for the sensor circuit is below normal, the fault code is displayed. The temperature for the oil is inaccurate. |
| 428-8 | Rear Axle Oil Temperature Sensor: Abnormal Frequency, Pulse Width, or Period | The sensor is a PWM sensor that operates at a frequency of approximately 500 ± 200 Hz. The sensor sends a PWM input signal to the ECM.
If the PWM frequency is outside the 500 ± 200Hz operating range, the diagnostic code will be activated. This code results from a failure of the sensor or an intermittent circuit connection. The temperature for the oil is inaccurate. |
| 1712-3 | Torque Converter Pedal Position Sensor: Voltage Above Normal | The torque converter pedal sensor is shorted to a +battery source or the sensor has failed internally. The output from the sensor will be constant, showing no output change as the angle of the pedal changes. |
| 1712-4 | Torque Converter Pedal Position Sensor: Voltage Below Normal | The torque converter pedal sensor is shorted to a ground source or the sensor has failed internally. The output from the sensor will be constant, showing no output change as the angle of the pedal changes. |
| 1712-8 | Torque Converter Pedal Position Sensor: Abnormal Frequency, Pulse Width, or Period | The sensor is a PWM sensor that operates at a frequency of approximately 500 ± 200 Hz. The sensor sends a PWM input signal to the ECM.
If the PWM frequency is outside the 500 ± 200 Hz operating range, the diagnostic code will be activated. This code results from a failure of the sensor or an intermittent circuit connection. The sensor is intermittently connected to the circuit or the sensor is damaged. Frequency output under these conditions will be erratic as the angle of the pedal is changed. |
| 1712-13 | Torque Converter Pedal Position Sensor: Out of Calibration | If the sensor is replaced, a calibration of the new sensor is required before the machine is operational. |
| 2974-3 | Brake Charge Pressure Sensor: Voltage Above Normal | The ECM monitors the ratio of the sensor output voltage and 5 VDC supply voltage. When output is greater than 97% for 0.5 seconds, a voltage high diagnostic code is issued. When the diagnostic code is active, the indicator for low brake pressure will be active. |
| 2974-4 | Brake Charge Pressure Sensor: Voltage Below Normal | When the ratio is less than 3% for 500 ms, the voltage low diagnostic is active. When the diagnostic code is active, the indicator for low brake pressure will be active. |
| 2874-8 | Brake Charge Pressure Sensor: Abnormal Frequency, Pulse Width, or Period | The sensor is a PWM sensor that operates at a frequency of approximately 500 ± 200 Hz. The sensor sends a PWM input signal to the ECM.
If the PWM frequency is outside the 500 ± 200 Hz operating range, the diagnostic code will be activated. This code results from a failure of the sensor or an intermittent circuit connection. When the diagnostic code is active, the indicator for low brake pressure will be active. |
| 2976-3 | Parking Brake Oil Pressure Sensor: Voltage Above Normal | If this Diagnostic Code is active, the system will use the solenoid state to determine whether the Parking Brake is engaged or disengaged. If machine speed is 0 and the transmission is in Neutral, the machine will apply the Parking Brake. |
| 2976-4 | Parking Brake Oil Pressure Sensor: Voltage Below Normal | If this Diagnostic Code is active, the system will use the solenoid state to determine whether the Parking Brake is engaged or disengaged. If machine speed is 0 and the transmission is in Neutral, the machine will apply the Parking Brake. |
| 2976-8 | Parking Brake Oil Pressure Sensor: Abnormal Frequency, Pulse Width, or Period | The sensor is a PWM sensor that operates at a frequency of approximately 500 ± 200 Hz. The sensor sends a PWM input signal to the ECM.
If the PWM frequency is outside the 500 ± 200 Hz operating range, the diagnostic code will be activated. This code results from a failure of the sensor or an intermittent circuit connection. The sensor is intermittently connected to the circuit or the sensor is damaged. If machine speed is 0 and the transmission is in Neutral, the machine will apply the Parking Brake. |
| 3440-3 | Front Service Brake Pressure Sensor: Voltage Above Normal (AKA - Park Brake Oil Pressure Sensor) | This diagnostic code is active when the signal wire is sending a voltage to the ECM that is above the expected range. The output is generally the result of the signal circuit being shorted to a sensor supply circuit. When this fault occurs, the park brake cannot be disengaged. |
| 3440-4 | Front Service Brake Pressure Sensor: Voltage Below Normal (AKA - Park Brake Oil Pressure Sensor) | This diagnostic code is active when the signal wire is sending a voltage to the ECM that is below the expected range. The output is generally the result of the signal circuit being shorted to a ground circuit. When this fault occurs, the park brake cannot be disengaged. |
| 3440-8 | Front Service Brake Pressure Sensor: Abnormal Frequency, Pulse Width, or Period (AKA - Park Brake Oil Pressure Sensor) | This diagnostic code is active when the signal wire is sending an abnormal frequency to the ECM.
If the PWM frequency is outside the 500 ± 200 Hz operating range, the diagnostic code will be activated. This code results from a failure of the sensor or an intermittent circuit connection. |
| 3442-3 | Rear Service Brake Oil Pressure Sensor: Voltage Above Normal | The ECM monitors the ratio of the sensor output voltage and 5 VDC supply voltage. When the output is greater than 97% for 0.5 seconds, a voltage high diagnostic is activated. |
| 3442-4 | Rear Service Brake Oil Pressure Sensor: Voltage Below Normal | When the ratio is less than 3% for 500 ms, the voltage low diagnostic is active. |
| 3442-8 | Rear Service Brake Oil Pressure Sensor: Abnormal Frequency, Pulse Width, or Period | The sensor is a PWM sensor that operates at a frequency of approximately 500 ± 200 Hz. The sensor sends a PWM input signal to the ECM.
If the PWM frequency is outside the 500 ± 200 Hz operating range, the diagnostic code will be activated. This code results from a failure of the sensor or an intermittent circuit connection. |
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.
Possible causes for an FMI 13 diagnostic code are:
- New software has been flashed to the ECM.
- The ECM has been replaced.
Note: Prior to beginning this procedure, use Cat® Electronic Technician (Cat ET) to check the status of the ECM power supply. If a diagnostic code is present, refer to the Sensor Supply - Test information to correct this problem before continuing.
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| Illustration 1 | g03651599 |
|
Schematic of the PWM sensor connections for the Transmission ECM | |
Note: The diagrams above are simplified schematics of the Transmission ECM connections. The schematics are electrically correct. However, not all of the possible harness connectors are shown. Refer to:
Electrical Schematic , UENR4996, "844K Wheel Dozer (T4F) Electrical System Schematic" for the complete machine schematic.
Electrical Schematic , UENR1697, "844K Wheel Dozer (LRC) Electrical System Schematic" for the complete machine schematic.
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| Implement ECM (MID 82) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 75-3 | Steering Oil Temperature Sensor: Voltage Above Normal | The sensor sends a PWM input signal to the ECM. The duty cycle of the signal varies from 5% to 95%. When the signal is above the expected range, the ECM issues the diagnostic code. This problem is generally the result of the signal wire in contact with another circuit. |
| 75-4 | Steering Oil Temperature Sensor: Voltage Below Normal | The sensor sends a PWM input signal to the ECM. The duty cycle of the signal varies from 5% to 95%. When the signal is below the expected range, the ECM issues the diagnostic code. This problem is generally the result of the signal wire in contact with another circuit. |
| 75-8 | Steering Oil Temperature Sensor: Abnormal Frequency, Pulse Width, or Period | This PWM sensor operates at a range of 500 ± 200 Hz. The sensor sends a PWM input signal to the ECM. The duty cycle of the signal varies from 5% to 95%.
If the PWM frequency is outside the 500 ± 200 Hz operating range, the diagnostic code will be activated. This code results from a failure of the sensor or an intermittent circuit connection. This type of fault is associated with a faulty sensor or a connection that is intermittent. |
| 290-3 | Engine Cooling Fan Pump Pressure Sensor: Voltage Above Normal | |
| 290-4 | Engine Cooling Fan Pump Pressure Sensor: Voltage Below Normal | |
| 290-8 | Engine Cooling Fan Pump Pressure Sensor: Abnormal Frequency, Pulse Width, or Period | |
| 434-3 | Hydraulic Pilot Oil Pressure Sensor: Voltage Above Normal | All functions dependent on pilot pressure are disabled. |
| 434-4 | Hydraulic Pilot Oil Pressure Sensor: Voltage Below Normal | All functions dependent on pilot pressure are disabled. |
| 434-8 | Hydraulic Pilot Oil Pressure Sensor: Abnormal Frequency, Pulse Width, or Period | All functions dependent on pilot pressure are disabled. |
| 767-3 | Fixed Implement Pump Oil Pressure Sensor: Voltage Above Normal | Valve calibrations will not work properly . |
| 767-4 | Fixed Implement Pump Oil Pressure Sensor: Voltage Below Normal | Valve calibrations will not work properly |
| 767-8 | Fixed Implement Pump Oil Pressure Sensor: Abnormal Frequency, Pulse Width, or Period | Valve calibrations will not work properly |
| 2475-3 | Right Joystick Forward/Reverse Position Sensor: Voltage Above Normal | All lift functions will stop working.
The joystick must be re-centered after the fault is cleared before the lift functions will start working again. |
| 2475-4 | Right Joystick Forward/Reverse Position Sensor: Voltage Below Normal | All lift functions will stop working.
The joystick must be re-centered after the fault is cleared before the lift functions will start working again. |
| 2475-8 | Right Joystick Forward/Reverse Position Sensor: Abnormal Frequency, Pulse Width, or Period | All lift functions will stop working.
The joystick must be recentered after the fault is cleared before the lift functions will start working again. |
| 2475-13 | Right Joystick Forward/Reverse Position Sensor: Out of Calibration | Poor modulation of the lift functions.
Float will not work properly. |
| 2477-3 | Right Joystick Left/Right Position Sensor: Voltage Above Normal | All tilt functions will stop working. .
The joystick must be re-centered after the fault is cleared before the tilt functions will start working again |
| 2477-4 | Right Joystick Left/Right Position Sensor: Voltage Below Normal | All tilt functions will stop working.
The joystick must be re-centered after the fault is cleared before the tilt functions will start working again. |
| 2477-8 | Right Joystick Left/Right Position Sensor: Abnormal Frequency, Pulse Width, or Period | All tilt functions will stop working.
The joystick must be re-centered after the fault is cleared before the tilt functions will start working again. |
| 2477-13 | Right Joystick Left/Right Position Sensor: Out of Calibration | Poor modulation of the tilt functions. |
| 3998-3 | Right Joystick Thumb Rocker Position Sensor: Voltage Above Normal | All tip functions will stop working.
The joystick must be re-centered after the fault is cleared before the tip functions will start working again. |
| 3998-4 | Right Joystick Thumb Rocker Position Sensor: Voltage Below Normal | All tip functions will stop working.
The joystick must be re-centered after the fault is cleared before the tip functions will start working again. |
| 3998-8 | Right Joystick Thumb Rocker Position Sensor: Abnormal Frequency, Pulse Width, or Period | All tip functions will stop working.
The joystick must be re-centered after the fault is cleared before the tip functions will start working again. |
| 3998-13 | Right Joystick Thumb Rocker Position Sensor: Out of Calibration | Poor modulation of the tip functions. |
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 Implement 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 Implement 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.
Possible causes for an FMI 13 diagnostic code are:
- New software has been flashed to the ECM.
- The ECM has been replaced.
Note: Prior to beginning this procedure, use Cat® Electronic Technician (Cat ET) to check the status of the ECM power supply. If a diagnostic code is present, refer to the Sensor Supply - Test information to correct this problem before continuing.
Note: Some test procedures may create additional diagnostic codes. Ignore these created diagnostic codes and clear the codes when the original diagnostic code has been corrected.
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| Illustration 2 | g03651614 |
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Schematic of the PWM sensor connections for the Implement ECM connections. | |
Note: The diagrams above are simplified schematics of the Implement ECM connections. The schematics are electrically correct. However, not all of the possible harness connectors are shown. Refer to:
Electrical Schematic , UENR4996, "844K Wheel Dozer (T4F) Electrical System Schematic" for the complete machine schematic.
Electrical Schematic , UENR1697, "844K Wheel Dozer (LRC) Electrical System Schematic" for the complete machine 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. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a troubleshooting procedure.
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| Troubleshooting Test Steps | Values | Results |
|---|---|---|
| 1. Identify The Active FMI Code Associated With The Sensor Circuit | Code present. |
FMI 3 diagnostic code, proceed to Test Step 2. FMI 4 diagnostic code, proceed to Test Step 6. FMI 8 diagnostic code, proceed to Test Step 9. FMI 13 diagnostic code, proceed to Test Step 17. |
| Begin Process For FMI 3 Troubleshooting HERE | ||
| 2. Check The Control And The Harness A. Turn key start switch and disconnect switch ON. B. Disconnect the machine harness from sensor. C. Refer to the schematic to determine the voltage source for the suspected faulty sensor. D. Measure voltage between signal and ground contacts at the machine harness connector for the sensor. |
Voltage is 8.0 ± 0.4 VDC, 10.0 VDC ± 0.95 VDC or 24 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: There may be an open or short in the machine harness. The open or short will be on the power or ground circuit wires. Repair or replace the machine harness. Check continuity of fuses when indicated on the schematic, as well. STOP |
| 3. Check For An Open In The Sensor Circuit A. The sensor remains disconnected from the machine harness. B. Turn the key start switch and the disconnect switch OFF. C. At the harness connector for the sensor, place a jumper wire between the ground contact and the signal contact. D. Disconnect J1 and J2 harness connectors from the ECM. E. At machine harness connector for sensor, measure the resistance from the signal contact to return contact. F. At the ECM Connector, gently pull on the wires and move the wires in a circular motion. Observe the resistance readings. Repeat the process for the sensor connector. |
The resistance is less than 5 Ω at all times during the manipulation of the harness. |
OK - The resistance is less than 5 Ω. The signal circuit and the ground circuits of the sensor are not open in the machine harness. Proceed to Test Step 4. NOT OK - Resistance reading for the signal circuit or the return circuit is greater than 5 Ω. Repair: Check the signal circuit or the ground circuit for opens or bad connections. Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. STOP |
| 4. Check Signal Circuit For A Short To +Battery A. The sensor and the ECM are disconnected from the harness. B. Turn the disconnect switch and the key start switch OFF. C. Measure the resistance between the signal and +battery contacts of the harness connector for the sensor. D. At machine harness connector J1 and J2 measure the resistance from signal contact to all possible sources of +battery. |
Resistance greater than 5K Ω for all readings. |
OK - The resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 5. NOT OK - The resistance less than 5 Ω for one or more of the readings. Repair: A short exists in the harness between the +battery and signal circuit. Repair or replace the machine harness. Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. STOP |
| 5. Check The Harness For A Short A. The disconnect switch and key start switch are OFF. B. The sensor and ECM are disconnected from harness. C. Measure the resistance from the signal wire to all other J1 and J2 contacts. |
Resistance is greater than 5K Ω for all readings. |
OK - The resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 16. NOT OK - The resistance less than 5 Ω. Repair: A short exists in the harness between the signal circuit and the circuit with the lower resistance measurement. Repair or replace the machine harness. Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a 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 4 Troubleshooting HERE | ||
| 6. Check The Control And The Harness A. Turn key start switch and disconnect switch ON. B. Disconnect the machine harness from the sensor. C. Refer to the schematic to determine the voltage source for the suspected faulty sensor. D. Measure voltage between signal and ground contacts at the machine harness connector for the sensor. |
Voltage is 8.0 ± 0.4 VDC, 10.0 ± 0.95 VDC, or 24 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: There may be an open or short in the machine harness. The open or short will be on the power or ground circuit wires. Repair or replace the machine harness. |
| 7. Check The Sensor A. With FMI 4 active, disconnect the sensor from the machine harness. B. Observe Cat ET or the Information Display for a code change as the sensor is disconnected and connected to harness. |
Code changes from FMI 4 to FMI 3. |
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 not the cause of the problem. Proceed to Test Step 8. |
| 8. Check The Signal Circuit For A Short To Ground A. Turn the key start switch and the disconnect switch OFF. B. Disconnect the J2 harness connector from the ECM. C. Measure the resistance between the signal contact for sensor and frame ground. |
The resistance is greater than 5K Ω. |
OK - The resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 16. NOT OK - The resistance is less than 5 Ω. A short circuit exists between frame ground and the signal circuit. Repair: Repair or replace the machine harness. Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a 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 | ||
| 9. Check The Control And The Harness A. Turn key start switch and disconnect switch ON. B. Disconnect the machine harness from sensor. C. Refer to the schematic to determine the voltage source for the suspected faulty sensor. D. Measure voltage between signal and ground contacts at the machine harness connector for the sensor. |
Voltage is 8.0 ± 0.4 VDC, 10.0 ± 0.95 VDC, or 24 VDC. |
OK - The voltage reading is correct for the suspected faulty sensor. Proceed to Test Step 10. NOT OK - The voltage is NOT correct for the circuit. Repair: There may be an open or short in the machine harness. The open or short will be on the power or ground circuit wires. Repair or replace the machine harness. |
| 10. Check Harness For An Open A. Turn the disconnect switch and the key start switch OFF. B. The sensor and ECM are disconnected from the harness. C. Connect a jumper wire from the end of the signal wire at the ECM to a known ground. D. Measure the resistance of the signal wire at ECM. |
The reading is less than 5 Ω. |
OK - The measurement is less than 5 Ω. Proceed to Test Step 11. NOT OK - The measurement is greater than 5K Ω. The signal circuit in the harness is open. Repair: Repair or replace the machine harness. Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. STOP |
| 11. Check The Signal Circuit For A Short To Ground A. Turn key start switch and disconnect switch OFF. B. Disconnect the J2 harness connector from the ECM. C. Measure resistance between signal contact for sensor and frame ground. |
Reading is greater than 5K Ω. |
OK - Measurement is greater than 5K Ω. Proceed to Test Step 12. NOT OK - Measurement is less than 5 Ω. The signal circuit in the harness is shorted to ground. Repair: Repair or replace the machine harness. Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. STOP |
| 12. Check The Sensor For A Short To Case A. Turn the key start switch and the disconnect switch OFF. B. At the machine harness connector for the sensor, measure the resistance between each pin and an unpainted location on the case of the sensor. |
The reading is greater than 5K Ω. |
OK - All measurements are greater than 5K Ω. Proceed to Test Step 13. NOT OK - A measurement is less than 5 Ω. The sensor has failed. Repair: Replace the sensor. Confirm that the new sensor corrects the problem. Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. STOP |
| 13. Check The Sensor For A Short To +Battery A. Disconnect the machine harness at the sensor. B. Turn the key start switch and the disconnect switch ON. C. At machine harness connector for J2 connector, measure the voltage between the signal pin of sensor and frame ground. |
The voltage is 0 VDC. |
OK - Voltage is 0 VDC. Proceed to Test Step 14. NOT OK - Significant voltage is present in circuit. Repair: Repair or replace the machine harness. STOP |
| 14. Check The Harness For A Short To +Battery A. Turn the key start switch and the disconnect switch ON. B. At machine harness connector for sensor, measure the voltage between each pin of sensor and frame ground (contacts 1, 2, and 3). |
The voltage is 0 VDC. |
OK - Voltage is 0 VDC. Proceed to Test Step 15. NOT OK - Significant voltage is present in circuit. Circuit shorted to +battery. Repair: Replace the sensor. Verify that the new sensor corrected the diagnostic code. STOP |
| 15. Check The Sensor A. Turn the key start switch and the disconnect switch ON. B. Use Cat ET or the Information Display to confirm the existence of the diagnostic code. C. Disconnect the sensor from machine harness. |
The diagnostic code is no longer present. |
OK - Diagnostic code is NO longer active. The sensor has failed. Repair - Replace the sensor. Verify new sensor corrected the diagnostic code. STOP NOT OK - The diagnostic code remains active. Proceed to Test Step 16. |
| 16. Check If The Diagnostic Code Remains. A. Turn the key start switch and the disconnect switch ON. B. Clear all diagnostic codes. C. Operate the machine. D. Stop machine and engage the safety lock lever. E. Check if the diagnostic code for the sensor is active. |
The code for the sensor is NO longer present. |
OK - The diagnostic code does not exist at this time. The initial diagnostic code may have been caused by a poor electrical connection or a short at one of the harness connections. Resume machine operation. STOP NOT OK - The diagnostic trouble code has not been corrected. Repair: Recheck the circuit and perform this procedure again. If the diagnostic code is still active, replace the sensor. If replacing the sensor does not correct the problem, the ECM may require replacement. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. Follow the procedure in Troubleshooting , "ECM - Replace" to replace the ECM. STOP |
| Begin Process For FMI 13 Troubleshooting HERE | ||
| 17. Check If The Diagnostic Code Remains. A. Perform the calibration procedure for the sensor. Refer to System Operation Testing and Adjusting, UENR4599, "844K Wheel Dozer (T4F & LRC) Calibrations" , for the correct calibration procedure. |
The calibration procedure was performed successfully. |
OK - The calibration procedure was performed successfully. Resume normal machine operation. STOP NOT OK - The calibration was not successful. Repair: Repeat the calibration procedure for the sensor. STOP |
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