AD30 and AD55 Underground Articulated Trucks Power Train Electronic Control System Caterpillar

Illustration 1	g01042827
Schematic of the body position sensor

This diagnostic code is associated with the body position sensor. This diagnostic code is recorded when the Power Train/Chassis Electronic Control Module (ECM) reads the Pulse Width Modulated (PWM) signal from the sensor.

Note: This diagnostic code is usually an intermittent condition. The diagnostic code may be active or the diagnostic code may not be active.

The possible causes of this condition are listed:

• The signal circuit is shorted to the +battery circuit or shorted to ground intermittently.

• The signal circuit is open intermittently or the sensor is disconnected.

• The sensor may have failed.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear these diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of CID 1175 FMI 08 is active before performing this procedure.

Note: Use the 146-4080 Digital Multimeter for the measurements in this procedure.

System Response:

The body snub function for the hoist system does not operate properly when the body is lowered. The gear of the machine is limited. The gear is limited to the current setting for the gear limit function. The hoist system will operate properly after the diagnostic code has been corrected.

Test Step 1. CHECK THE OPERATION OF THE SENSOR.

1. Turn the battery disconnect switch and the key start switch to the ON position.

2. Access the Caterpillar Electronic Technician (ET). View the display that is shown for the PWM duty cycle of the sensor signal. For more information about the ET, see Systems Operation, Troubleshooting, Testing and Adjusting, "Service Tools".

3. Disconnect the machine harness from the sensor. Observe the display and make a note of the display that is showing for the PWM duty cycle of the sensor signal.

4. At the machine harness for the sensor, install a jumper wire from contact B (wire 200-BK(Black)) to the signal contact C (wire E750-PU(Purple)). Observe the display and make a note of the display for the duty cycle of the sensor signal.

Expected Result:

The duty cycle that is shown for step "C." should be "OPEN/SHORTED HIGH". The duty cycle that is shown for step "D." should be "SHORTED TO GROUND".

Results:

• YES - The duty cycle for step "C." does read "OPEN/SHORTED HIGH" and the duty cycle for step "D." does read "SHORTED TO GROUND". Proceed to Test Step 2.

• NO - The duty cycle for step "C." does not read "OPEN/SHORTED HIGH" and the duty cycle for step "D." does not read "SHORTED TO GROUND".

  Repair: The sensor has failed. Replace the sensor.

  STOP

Test Step 2. CHECK THE SIGNAL CIRCUIT FOR AN OPEN.

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

2. The sensor remains disconnected from the machine harness.

3. Disconnect the J1 and J2 machine harness connectors from the ECM.

4. At the machine harness connector J1 and J2, measure the resistance from contact J2-18 (wire E750-PU(Purple)) to all possible sources of frame ground.

Expected Result:

The resistance should be less than 5 ohms.

Results:

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

• NOT OK - The resistance is not correct for one or more measurements.

  Repair: There is an open in the machine harness. Repair the machine harness or replace the machine harness. Verify that the problem has been corrected.

  STOP

Test Step 3. CHECK THE SIGNAL CIRCUIT FOR A SHORT.

1. The key start switch and the battery disconnect switch remain in the OFF position.

2. The machine harness remains disconnected from the sensor.

3. Remove the jumper wire from the previous Test Step.

4. At the machine harness connectors J1 and J2, measure the resistance from contacts J2-18 (wire E750-PU(Purple)) to all other J1 and J2 contacts.

Expected Result:

The resistance should be greater than 5 ohms for each measurement.

Results:

• YES - The machine harness is correct. Proceed to Test Step 4.

• NO - The resistance is not correct.

  Repair: There is a short in the machine harness. The short is between the circuit with the low resistance measurement and (wire E750-PU(Purple)). Repair the harness or replace the harness.

  STOP

Test Step 4. CHECK IF THE DIAGNOSTIC CODE REMAINS

1. Inspect the contacts of the harness connectors and clean the harness connectors.

2. Reconnect all the harness connectors.

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

4. Operate the machine.

5. Check the status of the CID 1175 FMI 08.

Expected Result:

The CID 1175 FMI 08 is active.

Results:

• YES - The CID 1175 FMI 08 is active. The diagnostic code has not been corrected. The ECM may have failed.

  Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Refer to Systems operation, Troubleshooting, Testing and Adjusting, "Electronic Control Module (ECM) - Replace" for the machine that is being serviced.

  STOP

• NO - The CID 1175 FMI 08 is not active. The diagnostic code does not exist at this time.

  Repair: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.

  STOP