938G Wheel Loader, 938G Series II Wheel Loader, IT38G Integrated Toolcarrier and IT38G Series II Integrated Toolcarrier Traction Control System MID 028 - CID 0607 - FMI 02 Caterpillar

Conditions Which Generate This Code:

Illustration 1	g00912710
This is a mini schematic of the wheel speed sensors.

This diagnostic code is for the speed sensor on the left rear axle. The diagnostic code is recorded when the ECM reads the sensor signal and the signal is erratic, intermittent, or incorrect.

This sensor is a frequency sensor that outputs a square wave from 1 Hz to 10 kHz. The frequency varies depending on the speed of the wheel that is monitored.

The possible causes of this diagnostic code are listed below.

• A poor electrical connection at a machine harness connector

• The sensor has failed.

• The signal circuit in the machine harness is shorted to ground.

• The signal circuit is shorted to the + battery in the machine harness.

• The signal circuit is open in the machine harness.

System Response:

The traction control system will be inoperable.

Test Step 1. CHECK THE SENSOR SUPPLY VOLTAGE AT THE SENSOR.

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

2. Measure the sensor supply voltage at the sensor. Measure the voltage between contact A (wire 709-OR) and contact B (wire A219-BK). Use the 7X-1710 Cable probes to measure the voltage. Do NOT disconnect the machine harness from the sensor.

Expected Result:

The voltage measures 10 DCV.

Results:

• OK - The voltage measures 10 DCV. The supply voltage is correct. Proceed to test step 3.

• NOT OK - The voltage does not measure 10 DCV. The supply voltage is not correct. Proceed to test step 2.

Test Step 2. CHECK THE SENSOR SUPPLY VOLTAGE AT THE TRACTION CONTROL ECM.

1. The disconnect switch and the key start switch remain on.

2. Measure the sensor supply voltage at the ECM. Measure the voltage between contact J2-9 (wire 709-OR) and contact J1-2 (wire A219-BK). Use the 7X-1710 Cable probes to measure the voltage. Do NOT disconnect the machine harness from the ECM for the traction control.

Expected Result:

The voltage measures 10 DCV.

Results:

• OK - The voltage measures 10 DCV. The supply voltage is correct. The machine harness has failed.

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

  Stop.

• NOT OK - The voltage does not measure 10 DCV. The supply voltage is not correct. The traction control ECM has failed.

  Repair: It is unlikely that the ECM has failed. Exit this test procedure and perform this procedure again. If the cause of the failure is not found, replace the ECM. Refer to the Testing and Adjusting, "Electronic Control Module (ECM) - Replace" section.

  Stop.

Test Step 3. CHECK FOR A SHORT TO GROUND IN THE SIGNAL CIRCUIT.

1. Turn the disconnect switch to the OFF position.

2. Disconnect the machine harness from the wheel speed sensor.

3. Disconnect the machine harness from the traction control ECM.

4. At the machine harness connector of the traction control ECM, measure the resistance between frame ground and contact J2-35 (wire E934-OR) of the signal circuit.

Expected Result:

The resistance is greater than 5000 ohms.

Results:

• OK - The resistance is greater than 5000 ohms. The harness circuit is correct. Proceed to test step 4.

• NOT OK - The resistance is less than 5 ohms. The machine harness has failed. There is a short between frame ground and the sensor signal circuit.

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

  Stop.

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

1. The disconnect switch remains in the OFF position.

2. The sensor remains disconnected from the machine harness and the traction control ECM remains disconnected from the machine harness.

3. At the machine harness connector for the traction control ECM, measure the resistance between the + battery contact J1-1 (wire 167-OR) and the contact J2-35 (wire E934-OR) of the sensor signal circuit.

Expected Result:

The resistance is greater than 5000 ohms.

Results:

• OK - The resistance is greater than 5000 ohms. The harness circuit is correct. Proceed to test step 5.

• NOT OK - The resistance is less than 5 ohms. The machine harness has failed. There is a short between the sensor signal circuit and the + battery circuit.

  Repair: Repair the harness or replace the harness.

  Stop.

Test Step 5. CHECK FOR AN OPEN SIGNAL CIRCUIT.

1. The disconnect switch remains in the OFF position.

2. The sensor remains disconnected and the traction control ECM remains disconnected.

3. Measure the resistance between contact C (wire E934-OR) of the sensor to the connector contact J2-35 (wire E934-OR) of the machine harness connector for the traction control ECM.

Expected Result:

The resistance is less than 5 ohms.

Results:

• OK - The resistance is less than 5 ohms. The signal circuit in the machine harness is correct. The traction control ECM has failed.

  Repair: It is unlikely that the ECM has failed. Exit this test procedure and perform this procedure again. If the cause of the failure is not found, replace the ECM. Refer to the Testing and Adjusting, "Electronic Control Module (ECM) - Replace" section.

  Stop.

• NOT OK - The resistance is greater than 5 ohms. The machine harness has failed. The sensor signal circuit is open in the machine harness.

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

  Stop.