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

MID 087 - Chassis ECM

CID 1175 - Body Position Sensor

FMI 04 - Voltage Below Normal

Illustration 1	g06351798
Body position sensor circuit

This diagnostic code indicates the Chassis ECM detects the body position sensor signal voltage is below normal.

The following can cause this code:

• Sensor failure

• Signal wire shorted to ground

• ECM failure

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 CID 1175 FMI 04 is active before performing this procedure.

System Response:

• The bed position causes an incorrect reading on the gauge

Test Step 1. CHECK THE MECHANICAL LINKAGE

Perform the body position sensor Testing and Adjusting procedure for the truck.

Expected Result:

The sensor mechanical linkage is operating properly.

Results:

• OK - The mechanical linkage is operating properly. Proceed to Test Step 2.

• NOT OK - The mechanical linkage is not operating properly.

  Repair: Repair the mechanical linkage.

  STOP

Test Step 2. TEST THE DUTY CYCLE OF THE BODY POSITION SENSOR

Use Cat^® Electronic Technician (Cat ET) to perform this test. For more information about Cat ET, see Troubleshooting, "Service Tools".

Note: This test is performed with the body in the DOWN position.

1. Turn on the disconnect switch and the keyswitch.

2. Ensure that the body is down completely.

3. Check the sensor duty cycle with Cat ET.
   Show/hide table

   Illustration 2	g02052606
   List of ECMs screen

   1. Select the "Chassis 793" from Cat ET.
      Show/hide table

      Illustration 3	g02052614
      Status tool screen

   2. Click the "Status" icon to view the status.
      Show/hide table

      Illustration 4	g02052615
      Hoist sensor screen

   3. View the information for the body position sensor duty cycle.

Expected Result:

The body position sensor duty cycle is greater than or equal to 2%.

Results:

• OK - The body position sensor duty cycle is greater than or equal to 2%. Proceed to Test Step 4.

• NOT OK - The body position sensor duty cycle is less than 2%. Proceed to Test Step 3.

Test Step 3. RECALIBRATE THE BODY POSITION SENSOR

1. Perform a body position sensor calibration.

Expected Result:

The body position sensor duty cycle is greater than or equal to 2%.

Results:

• OK - The body position sensor duty cycle is greater than or equal to 2%

  STOP

• Not OK - The body position sensor duty cycle is less than 2%. Proceed to Test Step 4.

Test Step 4. CHECK THE GROUND CIRCUIT

1. Turn off the keyswitch and the disconnect switch.

2. Remove the 7X-1710 Multimeter Probe.

3. Reconnect the harness to the sensor.

4. At the back of the harness connector for the sensor, insert the 7X-1710 Multimeter Probe at contact B.

5. Contact the other probe to frame ground.

6. Measure the resistance.

Expected Result:

Resistance is greater than 5 ohms.

Results:

• OK - Resistance is greater than 5 ohms. Proceed to Test Step 5.

• NOT OK - Resistance is less than 5 ohms.

  Repair: Repair or replace the harness.

  STOP

Test Step 5. CHECK FOR POWER AT THE SENSOR

The keyswitch and the disconnect switch remain off.

1. At the back of the harness connector for the sensor, insert a multimeter probe along contact A (wire 126-PK(Pink)) .

2. Turn on the disconnect switch and the keyswitch.

3. Measure the voltage from contact A (wire 126-PK(Pink)) to contact B (wire J765-BU(Blue)).

Expected Result:

The voltage is 8 VDC.

Results:

• OK - The voltage is 8 VDC. Proceed to Test Step 6.

• NOT OK - The voltage is not 8 VDC. The circuit is open. The sensor fuse may have failed.

  Repair: Check the sensor fuse. Replace the fuse if the fuse has no continuity.

  STOP

Test Step 6. CHECK THE SIGNAL CIRCUIT

1. Turn off the keyswitch and the disconnect switch.

2. Disconnect the harness from the sensor and Chassis ECM.

3. At the back of the harness connector for the sensor, insert a 7X-1710 Multimeter Probe along contact C.

4. At the back of the harness connector for the ECM , insert the other probe along contact J2-16.

5. Measure the resistance of signal (wire E750-PU(Purple))

Expected Result:

Resistance is greater than 5000 ohms.

Results:

• OK - Resistance is greater than 5000 ohms. Proceed to Test Step 7

• NOT OK - Resistance is less than 5000 ohms. The harness failed.

  Repair: Repair or replace the harness.

  STOP

Test Step 7. CHECK THE DIAGNOSTIC CODE

The keyswitch and the disconnect switch remain off.

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 ET, perform a wiggle test on the harness.

5. Turn on the disconnect switch and the keyswitch.

6. Operate the machine.

7. Check CID 1175 FMI 04 status.

Expected Result:

CID 1175 FMI 04 is not active.

Results:

• OK - CID 1175 FMI 04 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 1175 FMI 04 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