120M Series 2, 120M2, 12M Series 2, 12M Series II, 140M Series 2 and 160M Series 2 Motor Graders Implement Electronic Control System Caterpillar

Illustration 1	g02346939
Schematic of the main E/H pump pressure sensor

The CID 2828 diagnostic code is associated with the main hydraulic pump pressure sensor. The sensor produces an analog signal. The signal wire (N931-GY) connects to contact J1-36 of the Implement ECM 2. The FMI 04 diagnostic code is recorded when the Implement ECM reads the signal from the sensor (wire N931-GY) as being shorted to ground.

The possible causes of this diagnostic code are listed below:

• The signal circuit (wire N931-GY) is shorted to ground.

• The pressure sensor has failed.

• The ECM has failed. This condition is unlikely.

Note: Ensure that the CID 2828 FMI 04 diagnostic code 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.

Note: Ensure that all required calibrations are performed after the diagnostic code has been corrected.

Test Step 1. CHECK THE SENSOR

1. Turn the disconnect switch and the key start switch to the OFF position.

2. Disconnect the sensor from the machine harness.

3. Turn the disconnect switch and the key start switch to the ON position.

4. Observe the status of the CID 2828 FMI 04 diagnostic code.

Expected Result:

The CID 2828 FMI 04diagnostic code remains active and does not change.

Results:

• YES - The CID 2828 FMI 04diagnostic code remains active and does not change. The sensor is not causing the problem. Proceed to test step 2.

• NO - The CID 2828 FMI 04 diagnostic code is no longer active and has changed into an active CID 2828 FMI 03 diagnostic code. The sensor has failed.

  Repair: Replace the sensor. Verify that the new sensor corrects the problem.

  STOP

Test Step 2. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND.

1. The sensor remains disconnected from the machine harness.

2. Turn the key start switch and the disconnect switch to the OFF position.

3. Disconnect the J1 machine harness connector from the ECM.

4. At the J1 machine harness connector, measure the resistance from contact J1-36 (wire N931-GY) to ground.

Expected Result:

The resistance is greater than 5000 ohms.

Results:

• YES - The resistance is greater than 5000 ohms. The Implement ECM 2 may have failed.

  Repair: The failed condition of the ECM is unlikely. Recheck the status of the diagnostic code. If the diagnostic code remains present, exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Contact the Technical Communicator for your dealership for possible consultation with Caterpillar. prior to replacing the ECM. This consultation may greatly reduce repair time. If the ECM requires replacement, refer to Troubleshooting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - The resistance is less than 5000 ohms. The machine harness has failed. There is a short in the machine harness between the signal circuit and ground.

  Repair: Repair the machine harness or replace the machine harness.

  STOP