C0870

DTC C0870

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors
DTC C0870 03
- Device Voltage Reference Output 1 Circuit Voltage Below Threshold

DTC C0870 07
- Device Voltage Reference Output 1 Circuit Voltage Above Threshold

Diagnostic Fault Information





Circuit/System 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, center high mounted stop lamp (CHMSL), transmission control module (TCM), and engine control module (ECM). The stop lamps will not operate unless the ignition is in the ON position.

Conditions for Running the DTC

Battery voltage must be between 9-16 volts.

Conditions for Setting the DTC

* DTC C0870 03 will set when 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 will set when 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.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the brake pedal position sensor.
2. Ignition OFF, test for less than 1.0 ohm of resistance between the low reference circuit terminal C and ground.

• If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the BCM.

3. Ignition ON, test for 4.8 - 5.2 volts between the 5-volt reference circuit terminal A and ground.

• If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

• If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the BCM.

4. If all circuits test normal, test or replace the brake pedal position sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Brake Pedal Position Sensor Calibration
* Brake Pedal Position Sensor Replacement
* Control Module References for BCM replacement, setup, and programming Programming and Relearning