Conditions Which Generate This Code:
Schematic of the Door Switch (Implement Lockout)
This switch has two inputs to the ECM. One contact is normally open. The other contact is normally closed.
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 G943-BU) is shorted to ground.
- The "NORMALLY CLOSED" signal circuit (wire G944-YL) is shorted to ground.
- The Door 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 A (wire 200-BK) at the switch.
- Toggle the switch and note the status of the diagnostic code.
The diagnostic code is no longer active in either position.
- OK - The diagnostic code is no longer active in either position.
Repair: The Door Switch (Implement Lockout) has failed. Replace the switch. Verify that the new switch corrects the diagnostic code.
- 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
- Disconnect the negative battery cable and turn the key start switch to the OFF position.
- Disconnect the machine harness connectors from the ECM.
- At the harness connector for the ECM, measure the resistance between contact J2-37 (wire G943-BU) and frame ground.
- Measure the resistance between contact J2-29 (wire G944-YL) and frame ground.
The resistances should be greater than 5000 ohms.
- 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 cause of the diagnostic code is not found, contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
- 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.