CB64B, CB66B and CB68B Asphalt Compactors Machine Electronic Control System Caterpillar

Sensor Signal (Analog, Active) - Test

Usage:

Machine ECM

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

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Table 1
Machine ECM (MID 39)
SPN-FMI	Code Description	System Response
96-3	Fuel Level : Voltage Above Normal	Set Fuel Level to Zero, Do Not Indicate Low Fuel Fault Level - 1
96-4	Fuel Level : Voltage Below Normal	Set Fuel Level to Zero, Do Not Indicate Low Fuel Fault Level -1

Possible causes for an FMI 3 diagnostic code are:

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

Possible causes for an FMI 4 diagnostic code are:

The signal circuit for the sensor is shorted to ground.
The sensor has failed.
The ECM has failed. A failure of the ECM is unlikely.

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Illustration 1	g03831935
Machine ECM active analog connections

Note: The diagram above is a simplified schematic of the Machine ECM and the active analog connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of the Electrical Schematic, UENR6464 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. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a 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 2.
FMI 4 diagnostic code, proceed to Table 3.

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Table 2
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 sensor supply and sensor return. D. At the sensor harness connector, measure voltage between the sensor supply and sensor return.	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 circuit. Proceed to Test Step 2.
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 sensor harness connector, install 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. A short exists in the harness between the signal circuit and the circuit with the low resistance measurement. 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 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 3
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. C. At the ECM harness connector, measure the resistance between the sensor signal contact and all other contacts used in the ECM harness connectors.	The resistance is greater than 5K Ω.	OK - The resistance is greater than 5K Ω. The harness circuit is correct. Proceed to Test Step 3. NOT OK - The resistance is less than 5 Ω. A short circuit exists between the signal circuit and the circuit with the low resistance measurement. 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 a 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.