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| Illustration 1 | g03744821 |
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Connections of the Rear Inertial Measurement Sensor (Accelerometer) | |
This diagnostic code is associated with the Rear Inertial Measurement Sensor. The FMI 02 means that the ECM has detected that signal is Erratic, Intermittent, or Incorrect.
Note: Diagnostic Codes for components of the Rear AAC Controller are relayed to the Machine ECM via the CAN Data Link.
The possible causes of this failure are listed below:
- The sensor has failed.
- The Power to the sensor has failed.
- The signal circuit of the sensor is shorted to ground.
- The sensor circuit has an open.
- Without Vibe, the Sensor signal is outside of ±5g range.
- With Vibe, Sensor Voltage output is below 1000 mV or above 5000 mV.
- The ECM has failed. This situation is unlikely.
Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean and secure. Verify that all connections in the circuit are in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure. After making any possible fix to the circuit, cycle the Key Switch in order to determine if the Diagnostic Code still exists. Some Diagnostic Codes may not display until the engine is running. Verify that the CID 4320 FMI 02 is active before performing this procedure.
Use a digital multimeter for the measurements in this procedure.
System Response:
A Level 2 warning is generated.
Test Step 1. INSPECT THE SENSOR
- Perform a visual inspection of the sensor, the wiring for the sensor and the hardware that is associated with the sensor.
Note: The Front and Rear Inertial Measurement Sensors are identical. The sensors may be swapped to validate the failed part.
Expected Result:
There is no apparent damage to the sensor, the wiring for the sensor or the hardware that is associated with the sensor.
Results:
- YES - There is no apparent damage to the sensor, the wiring for the sensor or the hardware that is associated with the sensor. Proceed to Test Step 2.
- NO - There is apparent damage to the sensor, the wiring for the sensor or the hardware that is associated with the sensor.
Repair: Replace the damaged part.
STOP
Test Step 2. CHECK FOR POWER AT THE SENSOR
- Disconnect the sensor from the machine harness.
- Turn the key start switch and the disconnect switch to the ON position.
- At the harness connector for the sensor, measure the voltage from contact 1 (wire 163-WH(White)) to frame ground.
Expected Result:
The voltage is battery voltage.
Results:
- YES - The voltage is battery voltage. Proceed to Test Step 3.
- NO - The voltage is not battery voltage. The circuit is open.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 3. CHECK THE SENSOR CIRCUIT FOR AN OPEN CIRCUIT
- Turn the key start switch and the disconnect switch to the OFF position.
- Disconnect the machine harness connector from the sensor.
- At the machine harness connector for the sensor, connect a jumper wire from the power contact 1 (wire 163-WH(White) to the signal contact 2 (wire K427-OR(Orange)) .
- At the connector for the ECM, measure the resistance from the power contact 2 (wire 163-WH(White) to the signal contact 9 (wire K435-OR(Orange)) .
Expected Result:
The resistance measures less than 5 ohms.
Results:
- YES - The resistance measures less than 5 ohms. Proceed to Test Step 4.
- NO - The resistance measures greater than 5 ohms. There is an open or a poor connection in the circuit.
Repair: Check the signal circuit for an open or for a poor connection. Repair or replace the machine harness.
STOP
Test Step 4. CHECK THE SIGNAL CIRCUIT FOR A SHORT IN THE HARNESS
- The key start switch and the disconnect switch remain in the OFF position.
- Disconnect the Rear AAC Resistor from the machine harness.
- At the harness connector for the Rear AAC Controller, measure the resistance between contact 9 (wire K435-OR(Orange)) and all contacts that are used in the machine harness connectors for the Rear AAC Controller.
Expected Result:
Each resistance measurement is greater than 5000 ohms.
Results:
- YES - Each of the resistance measurements are greater than 5000 ohms. The circuit is correct. The sensor may have failed. Replace the sensor. If the Diagnostic Code is no longer present, resume normal operations. If the Diagnostic Code remains, proceed to Test Step 5.
- NO - The resistance is less than 5 ohms. The signal circuit is shorted to another circuit in the harness.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 5. CHECK IF THE DIAGNOSTIC CODE REMAINS
- Inspect the harness connectors and clean the contacts of the machine harness connectors.
- Reconnect all harness connectors.
- Turn the disconnect switch and the key start switch to the ON position.
- Propel the machine through the range of speeds and direction.
- Check the status of the CID 4320 FMI 02.
Expected Result:
The CID 4320 FMI 02 diagnostic code is no longer active.
Results:
- YES - The CID 4320 FMI 02 is not active. The diagnostic code does not exist at this time. The initial diagnostic code was probably caused by a poor connection or a short at one of the connectors that was disconnected and reconnected. Resume normal operation.
STOP
- NO - The CID 4320 FMI 02 is active. The diagnostic code has not been corrected. The ECM may have failed.
Repair: Failure of the ECM is unlikely. Exit this procedure and perform this procedure again. Prior to replacing an ECM, always contact your dealership 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