CW16 Pneumatic Compactor Machine Electronic Control System Caterpillar

Sensor Signal (PWM) - Test

Usage:

Machine ECM

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

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Table 1
Machine ECM (MID 39)
SPN-FMI	Code Description	System Response
521-2	Brake Pedal Position : Erratic, Intermittent, or Incorrect	Propel System Disabled Fault Level 2+
521-3	Brake Pedal Position : Voltage Above Normal	Propel System Disabled Fault Level 2+
521-4	Brake Pedal Position : Voltage Below Normal	Propel System Disabled Fault Level 2+
521-13	Brake Pedal Position : Out of Calibration	Limit To first Gear Fault Level 1

Pulse Width Modulation (PWM) is a technique for controlling analog circuits with digital outputs. 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.

Possible causes for an FMI 2 diagnostic code are:

A poor connection in the ground circuit.
A poor connection in the voltage supply circuit.
The sensor has failed.
The ECM has failed. A failure of the ECM is unlikely.

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 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 ECM has failed. A failure of the ECM is unlikely.

Possible causes for an FMI 13 diagnostic code are:

The sensor is out of calibration.
The ECM has failed. A failure of the ECM is unlikely.

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Illustration 1	g03867144
Machine ECM PWM Sensors

Note: The diagram above is a simplified schematic of the Machine ECM connections. The schematic is electrically correct. However, not all the possible harness connectors are shown.

For the full Electrical Schematic of the Pneumatic Compactors in this manual, refer to the appropriate media.

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Table 2
Brake Pedal Position Sensor
Low Idle Position	Mid-Point	High Idle Position
20% ±5%	50%	80% ±5%

The table above is a reference that can be used when checking the signal of the PWM sensors.

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. 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 2 diagnostic code, proceed to Table 3.
FMI 3 diagnostic code, proceed to Table 4.
FMI 4 diagnostic code, proceed to Table 5.
FMI 13 diagnostic code, proceed to Table 6.

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Table 3
FMI 2 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Check System Voltage At The ECM A. Turn the disconnect switch and the key start switch OFF. B. At the J1 harness connector for the ECM, insert a 7X-1710 Multimeter Probe along the power supply. Use the other multimeter probe to make contact to frame ground. C. Turn the disconnect switch ON. Start the engine and run at half throttle. D. Measure the voltage between the power supply contact and frame ground. E. Measure the voltage between the power supply contact and the (-) battery contact at the ECM harness connector.	Both voltages are approximately the same and are within range of the system voltage.	OK - Each voltage is approximately the same and is within range of the system voltage. Proceed to Test Step 6. NOT OK - The voltages are approximately the same, however the voltages are unstable. There is a large variation in the voltages. Proceed to Test Step 4. NOT OK - The positive battery contact to frame ground measurement is stable and within range of the system voltage. However, the measurement between the ECM positive battery contact and the ECM negative battery contact is not stable in the correct range always. Proceed to Test Step 2.
2. Check The Ground Circuits A. Turn the key start switch and the disconnect switch OFF. B. Disconnect the J1 harness connector from the ECM. C. At the J1 harness connector for the ECM, measure the resistance between each of the negative battery contacts and frame ground. The contacts for the negative battery connections are illustrated in the diagram at the beginning of this procedure.	Each resistance is less than 5.0 Ω.	OK - Each resistance is less than 5.0 Ω. Proceed to Test Step 3. NOT OK - A resistance is greater than 5k Ω. There is an open circuit or a poor connection in the ground circuit. Repair: Check all the connectors and splice points that are in the ground circuit. Ensure that all connections are clean, secure, and in good condition. Repair or replace the machine harness. Proceed to Test Step 4.
3. Check The Supply Circuits A. The key start switch and disconnect switch remain OFF. The ECM harness connector remains disconnected. B. At the J1 harness connector for the ECM, using a length of wire, measure the resistance between the alternator "B" terminal and each of the positive battery contacts that are connected to the J1 harness connector. The contacts for the five positive battery connections are illustrated in the diagram at the beginning of this procedure.	Each resistance is less than 5.0 Ω.	OK - Each resistance is less than 5.0 Ω. Proceed to Test Step 6. NOT OK - A resistance is greater than 5k Ω. There is an open circuit or a poor connection in the supply circuit. Repair: The open or poor connection is in the ground circuit. Check all the connectors and splice points that are in the ground circuit. Ensure that all connections are clean, secure, and in good condition. Repair or replace the machine harness. 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 currently. 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 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 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 currently. 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 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 currently. 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 6
FMI 13 Troubleshooting
Troubleshooting Test Steps	Values	Results
1. Check the Calibration A. Perform the calibration procedure for the sensor. Refer to the "Calibration" procedure in this manual. B. Observe the status of the diagnostic code.	The code is no longer active.	OK - The FMI 13 is no longer active. The calibration corrected the condition that caused the diagnostic code Proceed to Test Step 2. NOT OK -The FMI 13 Code is active. The diagnostic code has not been corrected. Verify that the correct software has been flashed into the ECM, or that the correct ECM is installed on the machine. Then repeat the calibration Proceed to Test Step 2.
2. 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 the machine and engage the safety lock lever. E. Check if the diagnostic code is active.	The diagnostic code is no longer present.	OK - The diagnostic code does not exist currently. 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.