Conditions Which Generate This Code:
| Illustration 1 | g03564276 |
Schematic 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 13 VDC to ground and a closed circuit will measure approximately 0 VDC to ground.
An FMI 03 diagnostic code is recorded when the status of both the inputs are open.
The possible causes of this diagnostic code are listed below:
- The return circuit (wire 200-BK) is open.
- Switch contact "1" signal circuit (wire A314-OR) is permanently open.
- Switch contact "3" signal circuit (wire F780-PK) is permanently open.
- The parking brake switch has failed.
- The ECM has failed. This is unlikely.
System Response:
The diagnostic indicator will flash. The park brake will be engaged.
Note: Ensure that the diagnostic code CID 70 - FMI 03 is active before performing this procedure.
Test Step 1. CHECK THE GROUND CIRCUIT AT THE SWITCH
- Disconnect the negative battery cable and turn the key start switch to the OFF position.
- Measure the resistance between switch contact "2" (wire 200-BK) 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 2.
- NOT OK - The resistance is greater than 5 ohms. Proceed to Test Step 4.
Test Step 2. CHECK THE SWITCH IN THE PRESSED POSITION
- Place the switch in the PRESSED 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 contact "2" and contact "3" and the resistance should be greater than 5000 ohms between contact "2" and contact "1".
Results:
- OK - The resistance is less than 5 ohms between contact "2" and contact "3" and the resistance is greater than 5000 ohms between contact "2" and contact "1". Proceed to Test Step 3.
- NOT OK - The resistance is not within an acceptable range. The switch has failed.
Repair: Replace the parking brake switch. Verify that the new switch corrects the diagnostic code.
STOP
Test Step 3. CHECK THE SWITCH IN THE RELEASED POSITION
- Place the switch in the RELEASED 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 greater than 5000 ohms between contact "2" and contact "3" and the resistance should be less than 5 ohms between contact "2" and contact "1".
Results:
- OK - The resistance is greater than 5000 ohms between contact "2" and contact "3" and the resistance is less than 5 ohms between contact "2" and contact "1". Proceed to Test Step 4.
- NOT OK - The resistance is not within an acceptable range. The switch has failed.
Repair: Replace the parking brake switch. Verify that the new switch corrects the diagnostic code.
STOP
Test Step 4. CHECK THE SIGNAL CIRCUITS FOR AN OPEN
- Disconnect the machine harness connectors from the ECM.
- Measure the resistance between contact J2-62 (wire F780-PK) and contact "3" (wire F780-PK) at the switch.
- Measure the resistance between contact J2-63 (wire A314-OR) and contact "1" (wire A314-OR) at the switch.
Expected Result:
The resistances should be less than 5 ohms.
Results:
- OK - The resistances are less than 5 ohms. Proceed to Test Step 5.
- NOT OK - The resistance is greater than 5 ohms on one of the readings.
Repair: The circuit with the high resistance is open in the machine harness. Repair the machine harness or replace the machine harness.
STOP
Test Step 5. CHECK THE SIGNAL CIRCUITS FOR A SHORT TO THE + BATTERY
- Measure the resistance between contact J2-62 (wire F780-PK) and contact 8 (wire 614-PU).
- Measure the resistance between contact J2-63 (wire A314-OR) and contact 8 (wire 614-PU).
Expected Result:
The resistances should be greater than 5000 ohms.
Results:
- OK - The resistances are greater than 5000 ohms.
Repair: Prior to replacing an ECM, always 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".
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 to a voltage source in the machine harness. Repair the machine harness or replace the machine harness.
STOP
