C0139

DTC C0138 or C0139

Circuit Description

The electronic brake control module (EBCM) uses the input from the brake fluid pressure sensor for more accurate braking control during vehicle stability enhancement system (VSES).

DTC Descriptors

This diagnostic procedure supports the following DTCs:

* DTC C0138 Base Brake System Pressure Circuit Low
* DTC C0139 Base Brake System Pressure Circuit High

Conditions for Running the DTC

DTC C0138

* The ignition is ON.
* Ignition voltage is greater than 8 volts.

DTC C0139

* The ignition is ON.
* Ignition voltage is greater than 8 volts.
* The vehicle speed is greater than 16 km/h (10 mph).

Conditions for Setting the DTC

DTC C0138

The vehicle speed exceeds 25 km/h (15 mph) then decelerates by 11.5 km/h (7 mph) per second and the brake pressure never increases.

DTC C0139

One of the following conditions occur:

* Brake pressure does not change after brake pedal has been applied twice.
* While brake pressure is greater than 50 psi, the vehicle speed exceeds 40 km/h (24 mph) and vehicle acceleration exceeds 8 km/h (5 mph) per second twice.

Action Taken When the DTC Sets

* The EBCM disables the PBA/TCS/VSES for the duration of the ignition cycle.
* The Traction Control and Active Handling indicator turns ON.
* The DIC displays the Service Stability System message.
* The ABS remains functional.

Conditions for Clearing the DTC

* The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
* The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids

* Find out from the driver under what conditions the DTC was set (when the DIC displayed the Service Active Handling message). This information will help to duplicate the failure.
* The Snapshot function on the scan tool can help find an intermittent DTC.
* Brake pressure sensor internal malfunction.

Test Description

The numbers below refer to the step numbers on the diagnostic table.
3. This step tests for the proper operation of the circuit in the low voltage range.
4. This step tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.
5. This step tests for a short to voltage in the 5-volt reference circuit.
6. This step tests for a high resistance or an open in the low reference circuit.

Step 1 - Step 8:

Step 9 - Step 16: