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| Illustration 1 | g00925916 |
Schematic of the Limit switch (parking brake)
This 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 0 DCV and a closed circuit will measure approximately 5 DCV.
An FMI 04 diagnostic code is recorded when the status of both the inputs are grounded.
The possible causes of this diagnostic code are listed below:
- The "NORMALLY OPEN" signal circuit (wire C743-PK) is shorted to ground.
- The "NORMALLY CLOSED" signal circuit (wire C744-PU) is shorted to ground.
- The parking brake switch has failed.
- The ECM has failed. This is unlikely.
Test Step 1. CHECK THE SWITCH
- Turn the key start switch to the ON position.
- The diagnostic code is active.
- Remove the wire from contact "COMMON" (wire J764-BR) at the switch.
- Toggle the switch and note the status of the diagnostic code.
Expected Result:
The diagnostic code is no longer active in either position.
Results:
- OK - The diagnostic code is no longer active in either position.
Repair: The parking brake switch has failed. Replace the switch. Verify that the new switch corrects the diagnostic code.
Stop.
- NOT OK - The diagnostic code is active in at least one of the positions. Proceed to Test Step 2.
Test Step 2. CHECK THE SIGNAL CIRCUITS FOR A SHORT TO GROUND
- Turn the key start switch to the OFF position.
- Disconnect the machine harness connectors from the ECM.
- Measure the resistance between contact J2-53 (wire C743-PK) and frame ground.
- Measure the resistance between contact J2-52 (wire C744-PU) and frame ground.
Expected Result:
The resistances should be greater than 5000 ohms.
Results:
- OK - The resistances are greater than 5000 ohms.
Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the diagnostic code is still present, replace the ECM. Refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
Stop.
- NOT OK - The resistance is less than 5000 ohms on one of the readings.
Repair: The circuit with the low resistance is shorted in the machine harness. Repair the machine harness or replace the machine harness.
Stop.