 | |
| Illustration 1 | g01766513 |
Thumb rocker position sensor connections | |
 | |
| Illustration 2 | g01930757 |
Location of the blade control handle | |
This diagnostic code is associated with the thumb rocker position sensor.
The FMI 04 diagnostic code is recorded when the ECM reads the voltage of the PWM signal from the thumb rocker position sensor as being below normal.
The possible causes of this diagnostic code are listed:
- The sensor signal circuit is shorted to ground.
- The sensor has failed.
- The ECM has failed. An ECM failure is unlikely.
System Response:
When the ECM activates diagnostic code for the position sensor, the angle functions for the blade will not operate.
Note: Ensure that the CID 1870 FMI 04 is active. This procedure can cause new diagnostic codes to be recorded. Ignore these created diagnostic codes. When the procedure is completed, clear the created diagnostic codes.
Test Step 1. CHECK THE SENSOR
- Turn the disconnect switch and the key start switch to the ON position.
- Ensure that the diagnostic code is active.
- Observe the status of the diagnostic code. Then, disconnect the sensor from the machine harness.
Expected Result:
If the sensor is faulty, the CID 1870 FMI 04 diagnostic code will become inactive and a CID 1870 FMI 03 diagnostic code will become active when the sensor is unplugged. The sensor is the cause of the diagnostic code if the CID 1870 FMI 04 diagnostic code is no longer active.
Results:
- OK - The diagnostic code remains active. The sensor is not faulty. The machine harness may have failed or the ECM may have failed. Proceed to Test Step 2.
- NOT OK - The diagnostic code is no longer active. The machine harness and the ECM are operating properly.
Repair: The sensor has failed. Replace blade control handle assembly. Verify that the new control handle corrects the problem.
STOP
Test Step 2. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND
- The sensor remains disconnected from the machine harness.
- Turn the key start switch and the disconnect switch to the OFF position.
- Disconnect the "J2" machine harness connector from the ECM.
- At the "J2" machine harness connector, measure the resistance from contact "J2-40" wire (K757-YL) to frame ground. Measure the resistance from contact "J2-40" wire (K757-YL) to all of the other contacts that are used in the ECM connectors.
Expected Result:
Each resistance measurement is greater than 5000 ohms.
Results:
- OK - Each resistance measurement is greater than 5000 ohms. The harness is correct. Proceed to Test Step 3.
- NOT OK - One or more of the resistance measurements is less than 5000 ohms.
Repair: The machine harness has failed. There is a short in the machine harness between the signal circuit and the circuit with the low resistance measurement. Repair the machine harness or replace the machine harness.
STOP
Test Step 3. CHECK THE STATUS OF THE DIAGNOSTIC CODE
- Inspect the contacts and clean the contacts of any harness connectors that are disconnected.
- Reconnect all harness connectors.
- Turn the disconnect switch and the key start switch to the ON position.
- Clear all inactive diagnostic codes.
- Operate the machine.
- Determine if the CID 1870 FMI 04 diagnostic code is active.
Expected Result:
The CID 1870 FMI 04 diagnostic code is active.
Results:
- YES - The CID 1870 FMI 04 diagnostic code is active. The problem has not been corrected. The ECM may have failed.
Repair: Check the sensor circuit again. Use the Caterpillar Electronic Technician (Cat ET) service tool in order to perform a wiggle test on the machine wiring harness. The wiggle test can detect momentary or intermittent shorts or opens in the machine wiring harness.If the cause of the problem is not found, the ECM may have failed. Prior to replacing an ECM, always contact the technical communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the cause of the diagnostic code is not found and the ECM must be replaced, refer to the Troubleshooting, "Electronic Control Module (ECM) - Replace" Section of this manual for details.
STOP
- NO - The CID 1870 FMI 04 diagnostic code is not active. The problem does not exist at this time.
Repair: The initial diagnostic code may have been caused by a poor electrical connection that was corrected when a harness connector was disconnected and reconnected
STOP