The PCM detects low voltage on the vehicle speed signal circuit for 45 seconds.
Action Taken When the DTC Sets
If equipped, the following actions occur
- The EBCM disables the ABS/TCS/DRP.
- The ABS indicator turns ON.
- The TRACTION OFF indicator turns ON.
- The red brake warning indicator turns ON.
- The DIC displays the SERVICE BRAKE SYSTEM message.
Conditions for Clearing the DTC
- Repair the condition responsible for setting the DTC.
- Use a scan tool in order to clear the DTC.
- After the DTC is cleared and the ignition is ON, the ABS indicator may remain ON until the EBCM completes a power-up self-test. This test concludes when the vehicle reaches a speed greater than 13 km/h (8 mph) and the wheel speeds are verified by the EBCM.
Diagnostic Aids
Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to TESTING FOR ELECTRICAL INTERMITTENTS , TESTING FOR INTERMITTENT AND POOR CONNECTIONS , WIRING REPAIRS and CONNECTOR REPAIRS in Wiring Systems.
Test Description
The numbers below refer to the step numbers on the diagnostic table
- 3. This step tests for a voltage signal from the PCM.
- 4. This step tests for a missing or erratic vehicle speed signal from the PCM. An assistant may be required to perform this test.
Scheme 32
Scheme 33
Circuit Description
As the front wheels spin, the wheel speed sensors produce an AC signal. The EBCM uses the frequency of the AC signal to calculate the wheel speed. The PCM converts the data from the vehicle speed sensor to a 128k pulses/mile signal. The EBCM uses the vehicle speed signal from the PCM in order to calculate the rear wheel speed.
Conditions for Running the DTC
The ignition is ON and the vehicle speed is between 24 km/h (15 mph) and 80 km/h (50 mph).
Conditions for Setting the DTC
The EBCM detects that one wheel speed input is 10 percent greater than or 10 percent less than the other wheel speed inputs within 3.2 km (2 mi) of driving.
If equipped, the following actions occur
- The EBCM disables the ABS/TCS/DRP.
- The ABS indicator turns ON.
- The TRACTION OFF indicator turns ON.
- The red brake warning indicator turns ON.
- The DIC displays the SERVICE BRAKE SYSTEM message.
The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.
Installing one tire of significantly different size on the vehicle causes DTC C0238 to set. Operating the vehicle with a tire that has very low air pressure may also set this DTC. Inspect the vehicle for an incorrect or damaged wheel speed sensor or vehicle speed sensor if the tires and the EBCM and PCM calibrations are OK.
The number below refers to the step number on the diagnostic table.
- 4. If the front tires are not the same size as the rear tires, the EBCM calibration must match the FRONT tire size and the PCM calibration must match the REAR tire size.
Scheme 34
The system relays are energized when the ignition is ON and the vehicle speed is greater than 6 km/h (4 mph). The system relay supplies voltage to the solenoid valves and to the pump motor. This voltage is referred to as the system voltage.
The EBCM controls the solenoid valves by grounding the control circuit.
- The ignition is ON.
- The vehicle speed is greater than 6 km/h (4 mph).
The EBCM detects an internal malfunction.