 | |
| Illustration 1 | g01252065 |
Right rear wheel speed sensor circuit | |
The CID 0608 FMI 02 diagnostic code is recorded when the brake ECM compares certain machine conditions to right rear wheel speed sensor data. The ECM will issue this diagnostic code if the sensor data is not within certain parameters.
Possible sensor conditions that can cause this diagnostic code are listed:
- Power supply for the sensor is faulty.
- Signal circuit is shorted to ground.
- Mechanical problems with the speed sensor.
- The sensor has failed.
- The ECM has failed. ECM failure is unlikely.
Before performing the following test steps, perform the following visual inspections:
- Verify that the sensor is mounted securely.
- Verify that the connectors are securely connected.
If the sensor mount and the contacts secure, but CID 0608 FMI 02 is active, proceed to the first test step.
Test Step 1. CHECK POWER SUPPLY CIRCUIT FOR THE SENSOR
- Disconnect the sensor from the harness.
- Turn the keyswitch and the disconnect switch to the ON position.
- At the harness connector for the sensor, measure the voltage between contact A (wire C985-BU) and the ground contact B (wire A235-BK).
Expected Result:
The voltage is 8V.
Results:
- OK - The voltage is 8V. The supply circuit is correct. Proceed to Test Step 2.
- NOT OK - The voltage is not 8V. Proceed to Test Step 2.
Test Step 2. CHECK FOR AN OPEN SIGNAL WIRE IN THE HARNESS.
Note: The sensor remains disconnected from the harness. The disconnect switch and the keyswitch remain in the OFF position.
- Disconnect the harness ECM connectors J1 and J2 from the ECM.
- At the harness connector for the sensor, connect a jumper between contact B (wire A235-BK) and contact C (wire 770-GN).
- At the harness ECM connectors, measure the resistance from contact J1-45 (wire A235-BK) to J2-33 (wire 770-GN).
Expected Result:
The resistance is less than 5 ohms.
Results:
- OK - The resistance is less than 5 ohms. The circuit is correct. Proceed to Test Step 3.
- NOT OK - The resistance is more than 5 ohms. There is an open or a faulty connection in the harness.
Repair: Consult the Electrical Schematic for this machine. Check all harness connectors in the speed sensor circuit. Ensure that the contacts of the connectors are clean, connected, and secure. After checking the connectors, repeat this test step. If the problem remains, check the wiring for a broken wire. Repair or replace the harness.
STOP
Test Step 3. CHECK FOR A SHORT IN THE SIGNAL CIRCUIT OF THE HARNESS.
Note: The harness connectors remain disconnected from the sensor and the ECM. Remove the jumper that was installed in the last step. The keyswitch and the disconnect switch remain in the OFF position.
- At the harness connector for the ECM, measure the resistance between contacts J2-33 (wire 770-GN) to all sources of ground on connectors J1 and J2.
Expected Result:
The resistance is greater than 5000 ohms.
Results:
- OK - The resistance is greater than 5000 ohms. Proceed to Test Step 5.
- NOT OK - A resistance is less than 5000 ohms. There between signal contact J2-33 (wire 770-GN) and one of the grounded wires in the harness.
Repair: Repair or replace the harness.
STOP
Test Step 4. CHECK THE SPEED SENSOR
Note: The keyswitch and the disconnect switch remain in the OFF position.
- Disconnect the harness from the sensor.
- At the sensor, measure resistance between contact A (wire C985-BU) and the sensor case or ground. Measure resistance between contact B (wire A235-BK) and the sensor case or ground. Measure resistance between contact C (wire 777-GN) and the sensor case or ground.
Expected Result:
Each measurement is greater than 10,000 ohms.
Results:
- OK - The resistance is greater than 10,000 ohms. Proceed to Test Step 5.
- NOT OK - The resistance is lesser than 10,000 ohms. The sensor has failed.
Repair: Replace the sensor.
STOP
Test Step 5. CHECK IF THE DIAGNOSTIC CODE REMAINS
- Inspect the contacts of the harness connectors in the sensor circuit. Ensure that the wires are securely connected to the contacts. Clean all of the contacts in the harness connectors.
- Reconnect all connectors.
- Turn the disconnect switch and the keyswitch to the ON position.
- Operate the machine.
- Check for an active CID 0608 FMI 02.
Expected Result:
CID 0608 FMI 02 is not active.
Results:
- OK - CID 0608 FMI 02 is not active. The failure is no longer present.
Repair: The diagnostic code was probably caused by a poor connection or a short at one of the harness connections that was disconnected and reconnected. Resume normal machine operation.
STOP
- NOT OK - The diagnostic code CID 0608 FMI 02 is active. Replace the left rear wheel speed sensor and if that does not remove the code then suspect the ECM.
Repair: Exit this procedure and perform this procedure again. If the cause of the failure is not found, contact your dealer Technical Communicator (TC) for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If ECM requires replacement, refer to Testing and Adjusting, "Electronic Control Module (ECM) - Replace" section of this manual.
STOP