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| Illustration 1 | g02747904 |
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Connections of the 8 VDC sensor supply | |
The sensor supply is a power supply that is internal to the ECM. The sensor supply provides 8 VDC to operate the sensors.
This diagnostic code will be recorded when the Brake ECM reads the voltage for the circuit of the sensor supply as being above normal.
The results of this diagnostic code are listed below:
- All of the associated sensors will also log faults.
The possible causes of the diagnostic code are listed below:
- The output of sensor supply has shorted to the +battery circuit.
- The Brake ECM has failed. This situation is unlikely.
Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean and secure. Verify that all connections in the circuit are in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure. The following test procedure may cause other diagnostic codes to be activated. Ignore these created diagnostic codes and clear the diagnostic codes when the problem has been corrected.
Test Step 1. CHECK THE VOLTAGE AT A COMPONENT
- Turn the disconnect switch and the key start switch to the ON position.
- Disconnect the machine harness connector from one of the sensors in Illustration 1.
- At the harness connector for one of sensors, measure the voltage from contact A (wire A700-OR(Orange)) to contact B (wire C243-BK(Black)).
Expected Result:
The voltage measurement is 8.0 ± 0.5 VDC.
Results:
- OK - The voltage measurement is 8.0 ± 0.5 VDC. The voltage is correct. Proceed to Test Step 4.
- NOT OK - The voltage measurement is greater than 8.0 ± 0.5 VDC. The measurement is not correct. Proceed to Test Step 2.
Test Step 2. CHECK FOR A SHORT CIRCUIT IN THE MACHINE HARNESS
- Turn the disconnect switch and the key start switch to the OFF position.
- Disconnect the machine harness connectors from the sensors in the illustration.
- Disconnect the machine harness connectors J1 and J2 from the ECM.
- At the harness connector J1 for the ECM, check the resistance from contact J1-44 (wire A700-OR(Orange)) to all other connections in the J1 and J2 harness connectors.
Expected Result:
Each resistance measurement is greater than 5000 ohms.
Results:
- OK - Each resistance measurement is greater than 5000 ohms. The supply circuit is not shorted to another circuit in the machine harness. Proceed to Test Step 3.
- NOT OK - One or more of the resistance measurements is less than 5000 ohms. There is a short in the machine harness.
Repair: The power supply circuit is shorted to another circuit in the machine harness. Refer to the Electrical System Schematic for the machine. Examine the supply circuit to determine the location of the problem.
For information on testing for short circuits and finding short circuits, refer to Testing and Adjusting, "Wiring Harness (Short Circuit) - Test". Repair the machine harness or replace the machine harness.
STOP
Test Step 3. CHECK THE POWER SUPPLY AT THE ECM
- Turn the disconnect switch and the key start switch to the OFF position.
- At the J1 connector for the ECM, use a wire removal tool to remove contact J1-44 (wire A700-OR(Orange)) and contact J1-45 (wire C243-BK(Black)) from the J1 connector. The machine harness connector J1 remains connected to the ECM.
- Turn the disconnect switch and the key start switch to the ON position.
- Use the multimeter probes to make contact on the connector pins. Measure the voltage at the ECM pins between the contact J1-44 and contact J1-45.
Expected Result:
The voltage measurement is 8.0 ± 0.5 VDC.
Results:
- OK - The voltage measurement is 8.0 ± 0.5 VDC. The voltage is correct. The ECM power supply is correct. Install the wires and sockets that were removed from the J1 connector back into the original locations. Proceed to Test Step 4.
- NOT OK - The voltage measurement is greater than 8.0 ± 0.5 VDC. The ECM power supply is not correct. The ECM has failed.
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 requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
Test Step 4. CHECK IF THE DIAGNOSTIC CODE REMAINS.
- Inspect the harness connectors. Clean the contacts of the harness connectors and check the wires for damage to the insulation that is caused by excessive heat, corrosion, or chafing.
- Perform a
45 N (10 lb) pull test on each of the wires that are associated with the circuit. - Reconnect all harness connectors to make sure that the connectors are fully seated. Also, make sure that the clips for each connector are fastened securely.
- Turn the disconnect switch and the key start switch to the ON position.
- Operate the machine.
- Check the status of the diagnostic code.
Expected Result:
The diagnostic code is active.
Results:
- YES - The diagnostic code is active. The diagnostic code has not been corrected.
Repair: A failure of the ECM is unlikely. Exit this procedure and perform this procedure again. Prior to replacing an ECM, contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NO - The diagnostic code is not active. The initial diagnostic code was probably caused by a poor electrical connection at one of the harness connectors. Resume normal machine operation.
STOP