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| Illustration 1 | g01449967 |
Schematic of the Auto/Manual HMU Switch | |
The Transmission Auto/Manual HMU switch has three inputs to the Transmission electronic control module (ECM). During normal operation, one input is grounded and the other inputs are open. A circuit failure is present when more than one input is grounded.
Note: Ensure that the diagnostic code of CID 0368 FMI 02 is active before performing this procedure.
Note: The following procedure can create other faults that can be detected by the Transmission ECM. Ignore these created faults and clear the created faults when the original diagnostic code is corrected.
Possible causes of this diagnostic code are listed:
- There is a harness fault.
- There is a failed switch.
Test Step 1. CHECK THE SWITCH CIRCUITS.
- Turn the disconnect switch and the key start switch to the OFF position.
- Disconnect the machine harness from the transmission ECM.
- At the machine harness connector for the transmission ECM, check the continuity to ground of the open contacts and the grounded contact for each position of the transmission auto/manual switch. Activate and deactivate each position of the transmission auto/manual switch.
Expected Result:
The continuity checks do not agree with the ground and open combinations.
Results:
- YES - The continuity checks do NOT agree with the ground and open combinations. The harness or the transmission auto/manual switch is faulty. Proceed to Test Step 2.
- NO - The continuity checks agree with the ground and open combinations. Proceed to Test Step 3.
Test Step 2. CHECK THE TRANSMISSION AUTO/MANUAL SWITCH.
- Disconnect the machine harness from the transmission auto/manual switch.
- Check the continuity to ground of the open contacts and the grounded contact for each position of the transmission auto/manual switch. Activate and deactivate each position of the transmission auto/manual switch.
Expected Result:
The continuity checks do not agree with the ground and open combinations.
Results:
- YES - The continuity checks do not agree with the ground and open combinations. The transmission auto/manual switch is faulty.
Repair: Repair the switch or replace the switch.
STOP
- NO - The continuity checks agree with the ground and open combinations.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 3. CHECK FOR A SHORT TO THE +BATTERY.
- At the machine harness connector for the transmission ECM, check the continuity from each switch contact to the contacts J1-33, J1-34, and J2-35.
Expected Result:
Continuity exists between one of the sources of the battery voltage and the switch circuit.
Results:
- YES - Continuity exists between one of the sources of battery voltage. The machine harness is faulty.
Repair: Repair the machine harness or replace the machine harness.
STOP
- NO - Continuity does not exist between one of the sources of battery voltage and the switch circuit. The machine harness is correct. It is unlikely that the transmission ECM is faulty. Exit this procedure and perform these procedures again.
Repair: If the cause is not found, replace the transmission ECM. Refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace" for more information on replacing the transmission ECM.
STOP