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| Illustration 1 | g01447474 |
Connections of the parking brake switch | |
The parking brake switch has two inputs to the ECM. The two inputs are normally open and normally closed. 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 and a closed circuit will measure approximately 0 DCV to ground.
The diagnostic code is recorded when the status of both of the inputs are open.
The possible causes of this diagnostic code are listed below:
- The return circuit (wire C216-BK) is open.
- The "Normally Open" contact (wire 419-YL) is permanently open.
- The "Normally Open" contact (wire G764-PK) is permanently open.
- The switch has failed.
- The ECM has failed. This 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 of 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.
| Status of the Switch | |||
|---|---|---|---|
| MODE | Switch Position | J2-53 wire 419-YL |
J2-52 wire G764-PK |
| Brake OFF | Up | Open | Closed |
| Brake ON | Down | Closed | Open |
System Response:
A level 2 warning will be generated. The ECM retains the last known good state until the parking brake switch is required. The machine is locked out until the diagnostic code is cleared.
Test Step 1. CHECK THE GROUND CIRCUIT FOR AN OPEN
- Turn the disconnect switch and the keyswitch to the OFF position.
- Disconnect the switch from the machine harness.
- Measure the resistance between frame ground and contact"Common" (wire C216-BK) at the connector for the switch.
Expected Result:
The resistance should be less than 5 ohms.
Results:
- OK - The resistance is less than 5 ohms. Proceed to Test Step 2.
- NOT OK - The resistance is greater than 5 ohms.
Repair: The return circuit (wire C216-BK) is open in the machine harness. Repair the machine harness or replace the machine harness.
STOP
Test Step 2. CHECK THE SWITCH
- Check for continuity between contact"Normally Closed" and contact "Common" of the switch.
- Press the switch. Release the switch and check for continuity.
- Check for continuity between contact "Common" and contact "Normally Open" of the switch.
- Press the switch. Release the switch and check for continuity.
Expected Result:
The continuity check agrees with Table 1.
Results:
- OK - The continuity check agrees. Proceed to Test Step 3.
- NOT OK - The continuity check does not agree. The switch has failed.
Repair: Replace the switch. Verify that the new switch corrects the diagnostic code.
STOP
Test Step 3. CHECK THE SIGNAL CIRCUITS FOR AN OPEN
- Reconnect the switch to the machine harness.
- Disconnect the J1 and J2 machine harness connectors from the ECM.
- At the machine harness connector for the ECM, check for continuity between contact J2-52 (wire G764-PK) and contact J1-70 (wire C216-BK).
- Press the switch. Release the switch and check for continuity.
- At the machine harness connector for the ECM, check for continuity between contact J2-53 (wire 419-YL) and contact J1-70 (wire C216-BK).
- Press the switch. Release the switch and check for continuity.
Expected Result:
The continuity check agrees with Table 1.
Results:
- OK - The continuity check agrees.
Repair: Reconnect the machine harness connectors. Verify that the diagnostic code has been corrected. If the cause of the problem is not found, contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Troubleshooting, "Electronic Control Module (ECM) - Replace".
STOP
- NOT OK - The continuity check does not agree. There is an open in the signal circuits of the machine harness.
Repair: There is an open in the machine harness. Repair the machine harness or replace the machine harness.
STOP