TH31-C9I, TH31-C9P, TH31-C9T, TH35-C11I, TH35-C13I, TH35-C13T, TH35-C15I and TH35-C15T Petroleum Power Train Packages and TH31-E61 and TH35-E81 Petroleum Transmissions Power Train Electronic Control System Caterpillar

Illustration 1	g01298952
Schematic of the position sensor

This diagnostic trouble code is associated with the position sensor. This diagnostic trouble code is recorded when the ECU reads the signal from the sensor as being shorted to the +battery. The sensor produces a PWM signal.

Possible causes of the diagnostic trouble code is listed:

• The supply circuit to the sensor is open.

• The return circuit is open.

• The signal circuit is shorted to the +battery.

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

• The sensor has failed.

• The ECU has failed. This is unlikely.

Note: The following test procedure may create other diagnostic trouble codes. Ignore these created diagnostic trouble codes and clear the diagnostic trouble codes when the original diagnostic trouble code has been corrected. Ensure that the diagnostic trouble code of CID 1824 FMI 03 is active before performing this procedure.

Note: Use a digital multimeter for the measurements in this procedure.

Test Step 1. CHECK THE VOLTAGE AT THE SENSOR.

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

2. Disconnect the sensor from the machine harness.

3. At the machine harness connector for the sensor, measure the voltage between contact A (wire 709-OR) and contact B (wire J765-BU).

Expected Result:

The voltage should measure approximately 8 DCV.

Results:

• OK - The voltage is approximately 8 DCV. Proceed to test step 4.

• NOT OK - The voltage is not approximately 8 DCV.

  Repair: There is a problem with the machine harness or the ECU has failed. It is unlikely that the ECU has failed.

  Proceed to test step 2.

Test Step 2. CHECK FOR AN OPEN IN THE SUPPLY CIRCUIT.

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

2. The sensor remains disconnected from the machine harness.

3. At the machine harness connector for the sensor, measure the voltage from contact A (wire 709-OR) to ground.

Expected Result:

The voltage should measure approximately 8 DCV.

Results:

• OK - The voltage measurement is approximately 8 DCV. Proceed to test step 3.

• NOT OK - The voltage does not measure approximately 8 DCV.

  Repair: The supply circuit is not correct. Repair the circuit or replace the circuit.

  STOP

Test Step 3. CHECK FOR AN OPEN IN THE RETURN CIRCUIT.

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

2. The sensor remains disconnected from the machine harness.

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

4. At the machine harness connector for the sensor, install a jumper wire from contact B (wire J765-BU) to ground.

5. At the machine harness connector for the ECU, measure the resistance from contact J2-22 (wire J765-BU) to ground.

Expected Result:

The resistance measurement should measure less than 5000 ohms.

Results:

• OK - The resistance measurement is less than 5000 ohms. The harness is correct.

  Repair: Check the circuit again. If the Caterpillar Electronic Technician (ET) is available, use the Cat ET service tool in order to perform a "Wiggle Test" on the machine wiring harness. The "Wiggle Test" can detect shorts and opens in the machine wiring harness that are momentary or intermittent. It is unlikely that the ECU has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic trouble code is not found, replace the ECU. Prior to replacing an ECU, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Unit - Replace".

  STOP

• NOT OK - The resistance that is measured is not correct.

  Repair: There is an open in the machine harness. The open is in the return circuit with the high resistance measurement. Repair the harness or replace the harness.

  STOP

Test Step 4. CHECK FOR AN OPEN IN THE SIGNAL CIRCUIT.

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

2. Disconnect the J1 and J2 machine harness connector from the ECU.

3. At the machine harness connector for the sensor, install a jumper wire from contact C (wire X955-GN) to contact B (wire J765-BU).

4. At the machine harness connector J1, measure the resistance from contact J2-26 (wire X955-GN) to contact J2-22 (wire J765-BU).

Expected Result:

The resistance should measure less than 5000 ohms.

Results:

• OK - The resistance measures less than 5000 ohms. Proceed to 5.

• NOT OK - The resistance measurement is greater than 5000 ohms.

  Repair: There is an open in the signal circuit. Repair the harness or replace the harness.

  STOP

Test Step 5. CHECK THE SIGNAL CIRCUIT FOR A SHORT.

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

2. The machine harness connectors J1 and J2 remain disconnected.

3. Remove the jumper wire from contact C (wire X955-GN) to contact B (wire J765-BU).

4. At the J1 and J2 machine harness connectors for the ECU, measure the resistance for the signal contact of the sensor J2-26 (wire X955-GN) to all other J1 and J2 contacts.

Expected Result:

Each resistance measurement should be greater than 5000 ohms.

Results:

• OK - Each resistance measurement is greater than 5000 ohms.

  Repair: The sensor has failed. Replace the sensor and verify that the new sensor corrected the problem. If the problem persists, exit this procedure and perform this procedure again.Check the circuit again. If the Caterpillar Electronic Technician (ET) is available, use the Cat ET service tool in order to perform a "Wiggle Test" on the machine wiring harness. The "Wiggle Test" can detect shorts and opens in the machine wiring harness that are momentary or intermittent. It is unlikely that the ECU has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic trouble code is not found, replace the ECU. Prior to replacing an ECU, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Unit - Replace".

  STOP

• NOT OK - The resistance measures less than 5000 ohms.

  Repair: There is a short in the machine harness. The short is between the signal circuit and the circuit with the low resistance measurement. Repair the harness or replace the harness.

  STOP