789D CMD Off-Highway Truck Chassis Electronic Control System (Command For Hauling) Caterpillar

MID 087 - Chassis ECM

CID 1494 - Steering Accumulator Oil Pressure Sensor

FMI 03 - Voltage Above Normal

Illustration 1	g06351803
Steering Accumulator Oil pressure sensor circuit

This diagnostic code indicates the "Chassis" ECM detects the Steering Accumulator Oil pressure sensor voltage is above normal.

This code can be caused by:

• Ground circuit failure

• Sensor failure

• Power circuit failure

• Harness failure

• ECM failure

Note: The following test procedure may create other diagnostic codes. Ignore these created codes and clear these created codes after the original diagnostic code has been corrected. Ensure diagnostic code CID 1494 FMI 03 is active before performing this procedure.

The sensor output frequency is approximately 500 Hz. The duty cycle of the signal is proportional to the pressure that is applied. The duty cycle varies from 3% to 95%.

Note: Use a calibrated digital multimeter for this procedure.

System Response:

Since the steering pressure value is unknown, the ECM commands the steering pump to full displacement.

Test Step 1. CHECK FOR POWER AT THE SENSOR

Do not disconnect the harness connector from the sensor.

1. Turn on the key switch and the disconnect switch.

2. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the voltage supply wire (contact A).

3. Measure the voltage from contact A to frame ground.

Expected Result:

The voltage is 8 VDC.

Results:

• OK - The voltage is 8 VDC. Proceed to Test Step 2.

• NOT OK - The voltage is not 8 VDC. The harness has failed.

  Repair: Replace or repair the harness.

  STOP

Test Step 2. CHECK FOR SENSOR GROUND

The harness remains connected to the sensor.

1. Turn off the key switch and the disconnect switch.

2. Remove the 7X-1710 Multimeter Probe from the voltage supply wire (contact A ).

3. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along the ground wire (contact B).

4. Measure the resistance from contact B to frame ground.

Expected Result:

The resistance is less than 5 ohms.

Results:

• OK - The resistance is less than 5 ohms. Proceed to Test Step 3.

• NOT OK - The resistance is greater than 5 ohms. The harness has failed.

  Repair: Replace or repair the harness.

  STOP

Test Step 3. CHECK HARNESS

The key switch and the disconnect switch remain in the off position.

1. Disconnect the harness from the sensor.

2. At the harness connector for the sensor, connect a jumper wire between contact B (wire J879-GN(Green)) and contact C (wire C450-YL(Yellow)).

3. Disconnect the harness connectors from the ECM.

4. At the harness connector for the ECM, measure the resistance between contact J2-41 (wire C450-YL(Yellow)) and contact J2-63 (wire J879-GN(Green)).

Expected Result:

The resistance is less than 5 ohms.

Results:

• OK - The resistance is less than 5 ohms. Proceed to Test Step 4.

• NOT OK - The resistance is greater than 5 ohms. The harness is open.

  Repair: Repair or replace the harness.

  STOP

Test Step 4. CHECK FOR A SHORT TO THE +BATTERY CIRCUIT

The key switch and the disconnect switch remain in the off position.

The harness remains disconnected from the sensor.

The harness connectors remain disconnected from the ECM.

1. Remove the jumper wire that was installed in the previous step.

2. At the harness connector for the ECM, measure the resistance from signal contact J2-41 (wire C450-YL(Yellow)) of the harness to all harness contacts used for the ECM.

Expected Result:

Each resistance is greater than 5000 ohms.

Results:

• OK - Each resistance is greater than 5000 ohms. Proceed to Test Step 5.

• NOT OK - A resistance is less than 5000 ohms. There is a short between signal contact J2-41 (wire C450-YL(Yellow)) and the circuit with the low resistance.

  Repair: Repair or replace the harness.

  STOP

Test Step 5. CHECK THE SENSOR OUTPUT

1. Reconnect the harness connectors to the ECM.

2. Reconnect the harness connectors to the sensor.

3. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe at the following:

   • Along signal wire (contact C)

   • Along ground wire (contact B)

4. Turn on the disconnect switch and the key switch.

5. Measure the sensor signal.

   The proper signal is described at the beginning of this procedure.

Expected Result:

The sensor signal is valid.

Results:

• OK - The sensor signal is valid. Proceed to Test Step 6.

• NOT OK - The sensor signal is not valid. The sensor has failed.

  Repair: Replace the sensor.

  STOP

Test Step 6. CHECK THE DIAGNOSTIC CODE

1. Inspect the harness.

   Clean the harness connector contacts.

   Inspect the harness connector contacts for corrosion or damage.

   Inspect the wire insulation for damage caused by heat, corrosion, or chafing.

2. Perform a 45 N (10 lb) pull test on each circuit wire.

3. Reconnect all harness connectors.

   Verify that the connectors are fully seated and the clips are fastened.

4. Check for intermittent problems. Using Cat^® Electronic Technician (Cat^® ET), perform a wiggle test on the harness.

5. Turn on the disconnect switch and the key switch.

6. Operate the machine.

7. Check CID 1494 FMI 03 status.

Expected Result:

CID 1494 FMI 03 is not active.

Results:

• OK - CID 1494 FMI 03 is not active.

  Repair: The initial diagnostic code was probably caused by a poor connection at one of the connectors that was checked.

  Resume normal operation.

  STOP

• NOT OK - CID 1494 FMI 03 is active. The ECM may have failed.

  Repair: Exit this procedure and perform this procedure again. Contact your technical communicator. If the ECM requires replacement, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP