349F and 352F Excavator Machine System Caterpillar

Sensor Signal (PWM) - Test

Usage:

Machine ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the PWM sensors of the machine.

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Table 1
Machine ECM (MID 299)
DTC	Code Description	System Response
586-12	Engine Speed Dial Switch : Bad Device or Component	This component communicates with the Machine ECM via a data link connection. If another code is active indicating a data link failure, troubleshoot the failure. If no data link code is active, replace the "Speed Dial" switch.
1657-3	Left Joystick Thumbwheel: Voltage Above Normal	The thumbwheel functions may be inoperable.
1657-4	Left Joystick Thumbwheel: Voltage Below Normal	The thumbwheel functions may be inoperable.
1657-8	Left Joystick Thumbwheel: Abnormal Frequency, Pulse Width, or Period	The thumbwheel functions may be inoperable.
1658-3	Right Joystick Thumbwheel: Voltage Above Normal	The thumbwheel functions may be inoperable.
1658-4	Right Joystick Thumbwheel: Voltage Below Normal	The thumbwheel functions may be inoperable.
1658-8	Right Joystick Thumbwheel: Abnormal Frequency, Pulse Width, or Period	The thumbwheel functions may be inoperable.
1956-3	Bucket Cylinder Position Sensor: Voltage Above Normal	The bucket functions may be inoperable.
1956-4	Bucket Cylinder Position Sensor: Voltage Below Normal	The bucket functions may be inoperable.
1956-8	Bucket Cylinder Position Sensor: Abnormal Frequency, Pulse Width, or Period	The bucket functions may be inoperable.
1968-3	Boom Cylinder Rod End Pressure Sensor: Voltage Above Normal	The boom cylinder cannot be lowered when requested.
1968-4	Boom Cylinder Rod End Pressure Sensor: Voltage Below Normal	The boom cylinder cannot be lowered when requested.
1968-8	Boom Cylinder Rod End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The boom cylinder cannot be lowered when requested.
1969-3	Boom Cylinder Head End Pressure Sensor: Voltage Above Normal	The boom cylinder cannot be raised when requested.
1969-4	Boom Cylinder Head End Pressure Sensor: Voltage Below Normal	The boom cylinder cannot be raised when requested.
1969-8	Boom Cylinder Head End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The boom cylinder cannot be raised when requested.
1971-3	Bucket Cylinder Head End Pressure Sensor: Voltage Above Normal	The bucket cylinder cannot be raised when requested.
1971-4	Bucket Cylinder Head End Pressure Sensor: Voltage Below Normal	The bucket cylinder cannot be raised when requested.
1971-8	Bucket Cylinder Head End Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	The bucket cylinder cannot be raised when requested.
2425-3	Boom Angle Sensor: Voltage Above Normal	Cat Grade Control (CGS) function may be unavailable.
2425-4	Boom Angle Sensor: Voltage Below Normal	Cat Grade Control (CGS) function may be unavailable.
2425-8	Boom Angle Sensor: Abnormal Frequency, Pulse Width, or Period	Cat Grade Control (CGS) function may be unavailable.
2425-20	Boom Angle Sensor: Data Drifted High	Cat Grade Control (CGS) function may be unavailable.
2425-21	Boom Angle Sensor: Data Drifted Low	Cat Grade Control (CGS) function may be unavailable.
2426-3	Stick Angle Sensor: Voltage Above Normal	Cat Grade Control (CGS) function may be unavailable.
2426-4	Stick Angle Sensor: Voltage Below Normal	Cat Grade Control (CGS) function may be unavailable.
2426-8	Stick Angle Sensor: Abnormal Frequency, Pulse Width, or Period	Cat Grade Control (CGS) function may be unavailable.
2426-20	Stick Angle Sensor: Data Drifted High	Cat Grade Control (CGS) function may be unavailable.
2426-21	Stick Angle Sensor: Data Drifted Low	Cat Grade Control (CGS) function may be unavailable.
2899-3	Main Hydraulic Pump #1 Displacement Sensor: Voltage Above Normal	Machine will not operate as requested.
2899-4	Main Hydraulic Pump #1 Displacement Sensor: Voltage Below Normal	Machine will not operate as requested.
2899-8	Main Hydraulic Pump #1 Displacement Sensor: Abnormal Frequency, Pulse Width, or Period	Machine will not operate as requested.
2900-3	Main Hydraulic Pump #2 Displacement Sensor: Voltage Above Normal	Machine will not operate as requested.
2900-4	Main Hydraulic Pump #2 Displacement Sensor: Voltage Below Normal	Machine will not operate as requested.
2900-8	Main Hydraulic Pump #2 Displacement Sensor: Abnormal Frequency, Pulse Width, or Period	Machine will not operate as requested.
3573-3	Pump #1 Negative Flow Control Pressure Reducer Pressure Sensor Voltage Above Normal	Engine speed of the machine will be lower than expected.
3573-4	Pump #1 Negative Flow Control Pressure Reducer Pressure Sensor Voltage Below Normal	Engine speed of the machine will be lower than expected.
3573-8	Pump #1 Negative Flow Control Pressure Reducer Pressure Sensor Abnormal Frequency, Pulse Width, or Period	Engine speed of the machine will be lower than expected.
3574-3	Pump #1 Negative Flow Control Pressure Reducer Pressure Sensor Voltage Above Normal	Engine speed of the machine will be lower than expected.
3574-4	Pump #1 Negative Flow Control Pressure Reducer Pressure Sensor Voltage Below Normal	Engine speed of the machine will be lower than expected.
3574-8	Pump #1 Negative Flow Control Pressure Reducer Pressure Sensor Abnormal Frequency, Pulse Width, or Period	Engine speed of the machine will be lower than expected.
4576-3	Bucket Angle Sensor: Voltage Above Normal	The bucket functions may be inoperable.
4576-4	Bucket Angle Sensor: Voltage Below Normal	The bucket functions may be inoperable.
4576-8	Bucket Angle Sensor: Abnormal Frequency, Pulse Width, or Period	The bucket functions may be inoperable.

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 is digital 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 3 Diagnostic code are:

The sensor has failed.
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 Machine 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 Machine 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 20 Diagnostic code are:

The sensor is not installed properly.
The power supply circuit for the sensor is open.
The return circuit is open.
The signal circuit is open or the sensor is disconnected.
The signal circuit is shorted to the sensor power supply.
The sensor has failed.
The Machine ECM has failed. A failure of the Machine ECM is unlikely.

Note: Make sure the sensor is installed properly. If the sensor is installed properly and the diagnostic code persists, proceed to the troubleshooting procedure for FMI 3.

Possible Causes for an FMI 21 Diagnostic code are:

The sensor is not installed properly.
The signal circuit for the sensor is shorted to ground.
The sensor has failed.
The Machine ECM has failed. A failure of the Machine ECM is unlikely.

Note: Make sure the sensor is installed properly. If the sensor is installed properly and the diagnostic code persists, proceed to the troubleshooting procedure for FMI 4.

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Illustration 1	g06118505
Machine ECM PWM sensors

The preceding diagram is a simplified schematic of the machine ECM connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic to view the entire circuitry of the machine.

Implement Control ECM

The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the PWM sensors of the machine.

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Table 2
Implement Control ECM (MID 272)
DTC	Code Description	System Response
1129-3	Right Side Attachment Pedal Sensor: Voltage Above Normal	The pedal will be inoperable.
1129-4	Right Side Attachment Pedal Sensor: Voltage Below Normal	The pedal will be inoperable.
1129-8	Right Side Attachment Pedal Sensor: Abnormal Frequency, Pulse Width, or Period	The pedal will be inoperable.
1130-3	Left Side Attachment Pedal Sensor: Voltage Above Normal	The pedal will be inoperable.
1130-4	Left Side Attachment Pedal Sensor: Voltage Below Normal	The pedal will be inoperable.
1130-8	Left Side Attachment Pedal Sensor: Abnormal Frequency, Pulse Width, or Period	The pedal will be inoperable.
1609-3	F2 Type Valve Load Sense Pressure Sensor: Voltage Above Normal	Squeeze function limiting will not operate.
1609-4	F2 Type Valve Load Sense Pressure Sensor: Voltage Below Normal	Squeeze function limiting will not operate.
1609-8	F2 Type Valve Load Sense Pressure Sensor: Abnormal Frequency, Pulse Width, or Period	Squeeze function limiting will not operate.

Possible Causes for an FMI 3 Diagnostic code are:

The sensor has failed.
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 Machine 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 Machine 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.

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Illustration 2	g06113120
Implement control ECM PWM sensors

The preceding diagram is a simplified schematic of the implement control ECM connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic to view the entire circuitry of the machine.

Diagnostic Trouble Code Procedure

Prior to beginning this procedure, use Cat^® Electronic Technician (Cat ET) Service Tool or the machine monitors to check for an active DTC 41 code. The DTC 41 indicates a failure of the 8 VDC power supply on the ECM. If the code is present, refer to the Sensor Supply - Test chapter to correct this problem before continuing. For transducers powered via the fuse panel, check the condition of the appropriate fuse before beginning the troubleshooting 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. For sensors powered via the fuse panel, check the condition of the appropriate fuse before beginning the troubleshooting procedure.

Identify the active FMI code associated with the components.
Determine which code is present and use the list below to determine which procedure to follow.

FMI 3 diagnostic code, proceed to Table 3.
FMI 4 diagnostic code, proceed to Table 4.
FMI 8 diagnostic code, proceed to Table 5.

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Table 3
FMI 3 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Check The Voltage At The Sensor A. Turn key start switch and disconnect switch ON. B. Refer to the schematic to determine the voltage source for the sensor. C. At the machine harness connector for the sensor, insert 7X-1710 multimeter probes along the contact of the sensor supply and along frame ground. D. At the sensor harness connector, measure voltage between the sensor supply and frame ground.	Voltage reading is correct for the sensor.	OK – The voltage reading is correct for the sensor. Proceed to Test Step 2. NOT OK – The voltage is NOT correct for the sensor. Repair: Examine all of the connectors that are in the circuit. Ensure that the connections are clean, secure, and are in good condition. Repair or replace the machine harness. Proceed to Test Step 4.
2. Check The Harness For An Open A. The key start switch and the disconnect switch remain in the OFF position. B. Disconnect the machine harness connector from the sensor. C. At the machine harness connector for the sensor, connect a jumper wire between the sensor return contact and signal contact. D. Turn the key switch and disconnect switch ON. E. Observe the status of the diagnostic code.	The diagnostic code changes from an FMI 3 to an FMI 4.	OK – The diagnostic code changes from an FMI 3 to an FMI 4. The sensor has failed. Repair: Replace the sensor. Proceed to Test Step 4. NOT OK – The diagnostic code does not change from an FMI 3 to an FMI 4. Proceed to Test Step 3.
3. Check Signal Circuit For A Short to +Battery A. Turn the key start switch and the disconnect switch to the OFF position. B. Disconnect the ECM harness connectors. The sensor harness connector remains disconnected. C. Remove the jumper wire that was installed in the previous test step. D. At the ECM harness connector, measure the resistance between the signal contact and all other +battery circuits used in the ECM harness connectors.	Each resistance is greater than 5K Ω.	OK - Each resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 4. NOT OK - The resistance is less than 5 Ω. Repair: A short exists in the harness between the signal circuit and the circuit with the low 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. Proceed to Test Step 4.
4. Check If The Diagnostic Code Remains A. Reconnect all harness connectors. Return machine to normal operating condition. B. Turn the key start switch and the disconnect switch ON. C. Clear all diagnostic codes. D. Operate the machine. E. Stop the machine and engage the safety lock. F. Check if the diagnostic code is active.	The diagnostic code is no longer present.	OK - The diagnostic code does not exist at this time. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. NOT OK - The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, 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 effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.

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Table 4
FMI 4 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Check The Sensor A. Turn the disconnect switch and the key start switch ON. B. Disconnect the sensor from the machine harness. C. Observe the status of the diagnostic code as the sensor is disconnected from the harness.	The code changes from an FMI 4 to an FMI 3 when the sensor is disconnected.	OK - The code changes from an FMI 4 to an FMI 3 when the sensor is disconnected. The sensor has failed. Repair: Replace the sensor. Proceed to Test Step 3. 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 2.
2. Check The Signal Circuit For A Short To Ground A. Turn the key start switch and the disconnect switch OFF. B. Disconnect the harness connectors from the ECM. The sensor remains disconnected from the machine harness. C. At the ECM harness connector, measure the resistance between the sensor signal contact and all possible sources of ground.	All resistance values are greater than 5K Ω.	OK - All resistance values are greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 3. NOT OK - One or more readings are less than 5 Ω. A short circuit exists between 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. Proceed to Test Step 3.
3. Check If The Diagnostic Code Remains A. Reconnect all harness connectors. Return machine to normal operating condition. B. Turn the key start switch and the disconnect switch ON. C. Clear all diagnostic codes. D. Operate the machine. E. Stop the machine and engage the safety lock . F. Check if the diagnostic code is active.	The diagnostic code is no longer present.	OK - The diagnostic code does not exist at this time. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. NOT OK - The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, 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 effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.

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Table 5
FMI 8 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Check The Signal Of The Sensor A. Turn the key start switch and disconnect switch to the OFF position. B. At the back of the harness connector for the sensor, insert multimeter probes along the signal contact and return contact. Note: Use Cat^® Electronic Technician (Cat ET) Service Tool if access to the sensor while operating the machine, is not safe. C. Turn the disconnect switch and the key start switch to the ON position. D. Monitor the signal of the sensor with a digital multimeter. E. Without disconnecting the sensor or the hardware that is associated with the sensor from the machine, take the sensor through the full operating range. Note: Refer to the table above for the proper signal.	The signal from the sensor responds in the manner that is described in the table above.	OK - The signal from the sensor responds correctly. The sensor is operating correctly. Proceed to Test Step 2. NOT OK - The signal from the sensor does not respond correctly. The sensor is not operating correctly. Repair: Replace the sensor. Proceed to Test Step 3.
2. Check For An Open In The Signal Circuit The key start switch and the disconnect switch remain in the OFF position. B. Disconnect the machine harness connector from the sensor. C. At the machine harness connector for the sensor, connect a jumper wire between the return contact and signal contact . D. Disconnect the machine harness connectors J1 and J2 from the ECM. E. At the ECM harness connector, measure the resistance between the signal contact and return contact.	The reading is less than 5 Ω.	OK - The measurement is less than 5 Ω. The signal and return circuit are correct. Proceed to Test Step 3. NOT OK - The measurement is greater than 5K Ω. The signal circuit in the harness is open. Repair: Repair or replace the machine harness. Proceed to Test Step 3.
3. Check If The Diagnostic Code Remains A. Reconnect all harness connectors. Return machine to normal operating condition. B. Turn the key start switch and the disconnect switch ON. C. Clear all diagnostic codes. D. Operate the machine. E. Stop the machine and engage the safety lock lever. F. Check if the diagnostic code is active.	The diagnostic code is no longer present.	OK - The diagnostic code does not exist at this time. The initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. STOP. NOT OK - The diagnostic trouble code has not been corrected. If the diagnostic code has not been corrected after performing the procedure a second time, 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 effect repair time. Follow the steps in Troubleshooting, "ECM - Replace" if the ECM needs to be replaced. STOP.