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| Illustration 1 | g01275678 |
Auto retarder control (ARC) ON/OFF switch circuit | |
This switch has two inputs to the brake ECM. During normal operation, one of the inputs is open and the other is grounded.
Note: When the circuit is measured with a voltmeter, an open circuit will measure approximately 13V and a closed circuit will measure approximately 0V.
A CID 0713 FMI 03 diagnostic code is recorded when both inputs are open.
The possible causes of this diagnostic code are listed below:
- The return circuit (wire A294-BK) is open.
- The "N/O" signal circuit (wire K986-PK) is open.
- The "N/C" signal circuit (wire K985-BR) is open.
- The "N/O" signal circuit (wire K986-PK) is shorted to the + battery.
- The "N/C" signal circuit (wire K985-BR) is shorted to the + battery.
- The ARC ON/OFF switch has failed.
- The ECM has failed.ECM failure is unlikely.
Test Step 1. CHECK THE GROUND CIRCUIT AT THE SWITCH
- Turn the keyswitch to the OFF position.
- Measure the resistance between contact 2 (wire A294-BK) at the switch and frame ground.
Expected Result:
The resistance should be less than 5 ohms.
Results:
- OK - The resistance is less than 5 ohms. Proceed to Test Step 3.
- NOT OK - The resistance is greater than 5 ohms. Proceed to Test Step 2.
Test Step 2. CHECK THE GROUND CIRCUIT FOR AN OPEN
- Disconnect the harness connector J1 from the brake ECM.
- Measure the resistance between contact J2-63 (wire A294-BK) and contact 2 (wire A294-BK) at the switch.
Expected Result:
The resistance should be less than 5 ohms.
Results:
- OK - The resistance is less than 5 ohms. The ECM may have failed, however, ECM failure is unlikely.
Repair: Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, contact your Cat® dealer. If ECM replacement is required, refer to the Testing and Adjusting, "Electronic Control Module (ECM) - Replace" section of this manual.
STOP
- NOT OK - The resistance is greater than 5 ohms.
Repair: The return circuit (wire A294-BK) is open. Repair or replace the harness.
STOP
Test Step 3. CHECK THE SWITCH IN THE OFF POSITION
- Place the switch in the OFF position.
- Measure the resistance between contact 2 and contact 1 of the switch.
- Measure the resistance between contact 2 and contact 3 of the switch.
Expected Result:
The resistance should be less than 5 ohms between contacts 1 and 2. The resistance should be greater than 5000 ohms between contacts 2 and 3.
Results:
- OK - The resistance is less than 5 ohms between contacts 1 and 2. The resistance is greater than 5000 ohms between contacts 2 and 3. Proceed to Test Step 4.
- NOT OK - The resistance is not within an acceptable range. The switch has failed.
Repair: Replace the switch. Verify that the new switch corrects the diagnostic code.
STOP
Test Step 4. CHECK THE SWITCH IN THE ON POSITION
- Place the switch in the ON position.
- Measure the resistance between contacts 2 and 1 of the switch.
- Measure the resistance between contacts 2 and 3 of the switch.
Expected Result:
The resistance should be greater than 5000 ohms between contacts 1 and 2. The resistance should be less than 5 ohms between contacts 2 and 3.
Results:
- OK - The resistance is greater than 5000 ohms between contacts 1 and 2. The resistance is less than 5 ohms between contacts 2 and 3. Proceed to Test Step 6.
- NOT OK - The resistance is not within an acceptable range. The switch has failed.
Repair: Replace the switch. Verify that the new switch corrects the diagnostic code.
STOP
Test Step 5. CHECK THE SIGNAL CIRCUITS FOR AN OPEN
- Disconnect the harness connector J1 from the brake ECM.
- Measure the resistance between contact J1-40 (wire K985-BR) and contact 1 (wire K985-BR) at the switch.
- Measure the resistance between contact J1-33 (wire K986-PK) and contact 3 (wire K986-PK) at 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 6.
- NOT OK - The resistance is greater than 5 ohms on one of the readings.
Repair: The circuit with the high resistance is open. Repair or replace the harness.
STOP
Test Step 6. CHECK THE SIGNAL CIRCUITS FOR A SHORT TO THE + BATTERY
- Measure the resistance between contact J1-40 (wire K985-BR) and contact J1-31 (wire 176-RD).
- Measure the resistance between contact J1-33 (wire K986-PK) and contact J1-31 (wire 176-RD).
Expected Result:
The resistance is greater than 5000 ohms.
Results:
- OK - The resistance is greater than 5000 ohms. The ECM may have failed, however, ECM failure is unlikely.
Repair: Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, contact your Cat dealer. If the ECM must be replaced, refer to the Testing and Adjusting, "Electronic Control Module (ECM) - Replace" section of this manual.
STOP
- NOT OK - The resistance is less than 5000 ohms on at least one of the readings.
Repair: The circuit with the low resistance is shorted. Repair or replace the harness.
STOP