New for many 2012 and later model year GM passenger cars and trucks equipped with an automatic transmission is the Electronic Brake Pedal Override feature, which reduces engine power if it detects that the brake pedal is applied while the accelerator is also applied. The Electronic Brake Pedal Override uses a dual Brake Pedal Position (BPP) sensor (two sensors in one). The dual BPP sensor replaces the old style open/closed brake switch that has been used for years.
The dual BPP sensor (Fig. 1) is actually two separate variable resistors (two separate potentiometers activated by the same connection to the brake pedal arm), each working similarly to a Throttle Position Sensor. The resistors are housed in the same part and are not replaceable separately. The dual BPP sensor has three wires leading to the ECM and three different wires leading to the BCM.
After various service repairs, the dual BPP sensor requires a relearn procedure in both the BCM and ECM (for example, on 2012 Escalade, Avalanche, Express, Silverado, Suburban, Tahoe, Savana, Sierra, and Yukon models: BCM relearn – Service Information Document ID 1835636 and ECM relearn – Service Information Document ID 2655204). The relearn procedures will set the dual BPP sensor’s home values.
The BCM’s value is used to determine the action of the driver applying the brake pedal and to provide this information to the vehicle’s subsystems via the GMLAN communication bus. The ECM’s value is used for the new Electronic Brake Pedal Override feature.
The following service repairs will require a dual BPP sensor relearn:
• Replacement or removal of the brake pedal hardware
• Replacement or removal of the Brake Pedal Position sensor
• ECM replacement and/or reprogram
• BCM replacement and/or reprogram
• Installation of any GM accessory that requires programming of the ECM or BCM.
Symptoms of an unlearned or incorrectly learned dual BPP sensor include:
• DTC C0161 (ABS Brake Switch Circuit) will set in the Electronic Brake Control Module (EBCM)
• Service Stability message
• DTC C0277 Sym4B (Brake Master Cylinder Piston Position Sensor) – Home position not learned
• Brake lights stay on without brake pedal applied
• Must press down farther than normal on the brake pedal to disengage the cruise control
• Must press down farther than normal on the brake pedal to turn on the brake lights
• Unwanted Electronic Brake Pedal Override activation (low power, feels like the vehicle is in a traction control or stability control event). If the Traction Control System (TCS) is turned off, the condition will not be present. There will be no indication to the driver that the system is active.
TIP: Other items that may disable the Electronic Brake Pedal Override include TCS disable, Vehicle Stability Enhancement System disable, 4WD Low range, and automatic transmission ranges M3, M2, and M1.
If any of the above conditions are experienced, perform a dual BPP sensor relearn procedure for the BCM and ECM.
- Thanks to James Will and Jack Woodward