LIGHTING GP- 3157252 - Caterpillar

Illustration 1 g06003439
Connections of the Parking Brake Switch
The Parking Brake Switch has two inputs to the ECM. During normal operation, one of the inputs is open. The other input is grounded. When a circuit is measured with a voltmeter, an open circuit will measure approximately 8 DCV to ground. When a circuit is measured with a voltmeter, a closed circuit will measure approximately 0 DCV to ground.The diagnostic code is recorded when the status of both inputs are open.The possible causes of this diagnostic code are listed below:
The return circuit (wire A273-BK(Black)) is open.
The "Normally Open" contact (wire U734-GN(Green)) is permanently open.
The "Normally Closed" contact (wire U735-GY(Grey)) is permanently open.
The switch has failed.
The ECM has failed. This situation is unlikely.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 the connections in the circuit are clean and secure. 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 create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 0070 FMI 03 is active before performing this procedure.
Table 1
Status of the Switch
MODE Switch Position J2-55
wire U734-GN(Green) J2-54
wire U735-GY(Grey)
Brake OFF Up Open Closed
Brake ON Down Closed Open Test Step 1. CHECK THE GROUND CIRCUIT OF THE SWITCH IN THE HARNESS
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness connectors from the ECM.
Measure the resistance between contact J1-70 (wire A273-BK(Black)) of the machine harness for the ECM and the contact 2 (wire A273-BK(Black)) at the switch harness connector.Expected Result:The resistance is less than 5 ohms.Results:
OK - The resistance is less than 5 ohms. The circuit is correct. Proceed to Test Step 2.
NOT OK - The resistance is greater than 5 ohms. The circuit is open. The machine harness has failed.Repair: Repair the machine harness or replace the machine harness.STOPTest Step 2. CHECK THE SWITCH CIRCUITS FOR A SHORT TO THE +BATTERY CIRCUIT
The machine harness connectors remain disconnected from the ECM.
The disconnect switch and the key start switch remain in the OFF position.
Disconnect contact N/O (wire U734-GN(Green)) and contact N/C (wire U735-GY(Grey)) from the connector of the switch.
At the machine harness ECM connector, measure the resistance from contact J2-54 (wire U735-GY(Grey)) to all contacts used in the ECM machine harness connectors.
At the machine harness ECM connector, measure the resistance from contact J2-55 (wire U734-GN(Green)) to all contacts used in the ECM machine harness connectors.Expected Result:Each resistance measurement is greater than 5000 ohms.Results:
OK - Each resistance measurement is greater than 5000 ohms. The harness is correct. Proceed to Test Step 3.
NOT OK - One or more of the measurements were less than 5000 ohms. There is a short in the machine harness.Repair: The short is between wire U735-GY(Grey)and the circuit