C0870 - Lighting Systems
DTC C0870
CIRCUIT DESCRIPTION
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The brake pedal position sensor provides an analog voltage signal that will increase as the brake pedal is applied. The body control module (BCM) provides a low reference signal and a 5-volt reference voltage to the brake pedal position sensor. When the variable signal reaches a voltage threshold indicating the brakes have been applied, the BCM will apply battery positive voltage to the stop lamps, transmission control module (TCM), engine control module (ECM), and stop lamp relay coil side. The BCM also supplies the stop lamp relay coil with ground. When the stop lamp relay receives battery voltage and ground from the BCM, the relay coil is energized and the stop lamp relay switch contacts close applying battery voltage through the STOP/B/U/LPS fuse to illuminate the center high mounted stop lamp (CHMSL).
DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC C0870 Device Voltage Reference Output 1 Circuit
This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description. DTC Symptom Description
CONDITIONS FOR RUNNING THE DTC
Ignition voltage is within the normal operating voltage range.
CONDITIONS FOR SETTING THE DTC
- DTC C0870 03-The BCM detects a short to ground in the brake pedal position sensor voltage reference circuit for 0.5 seconds or greater
- DTC C0870 07-The BCM detects a short to battery voltage in the brake pedal position sensor voltage reference circuits for 0.5 seconds or greater
ACTION TAKEN WHEN THE DTC SETS
- The Service Vehicle Soon indicator is commanded ON.
- If the DTC sets while the vehicle is running, the BCM will activate the brake lights when the vehicles transmission is not in the PARK position and the vehicle is not accelerating.
CONDITIONS FOR CLEARING THE DTC
- The condition responsible for setting the DTC no longer exists.
- You issue a scan tool CLEAR DTCs command.
- A history DTC will clear once 50 malfunction-free ignition cycles have occurred.
- A DTC will not clear the current status until the next ignition cycle.
DIAGNOSTIC AIDS
IMPORTANT: The stop lamps will not illuminate unless the ignition is in the ON position. For more detailed information concerning stop lamp operation, refer to Exterior Lighting Systems Description and Operation.
Thoroughly inspect the wiring and connectors. An incomplete inspection of the wiring and connectors may result in misdiagnosis causing part replacement with the reappearance of the malfunction. If an intermittent malfunction exists, refer to Diagnostic Aids for Circuit Testing and Wiring Repair procedures.
TEST
