Normal Operation

The ABS module monitors the Brake Pedal Position (BPP) switch in combination with other brake inputs: wheel speed sensors, brake pressure transducer and lateral accelerometer from the sensor cluster. The pedal position signal is used by the ABS module for various diagnostic routines as well as to determine system functionality. The BPP  signal is provided by the stoplamp switch and can be monitored via the brake on/off (BOO_ABS) PID and should match the actual brake pedal position. The ABS module receives the stoplamp switch information from the PCM over the High Speed Controller Area Network (HS-CAN) bus.

• DTC C1446 (Brake Switch Circuit Failure) - If the stoplamp switch status from the PCM is not received by the ABS module due to a failure of the stoplamp switch or the HS-CAN  bus, the ABS module will set DTC C1446. The ABS module uses a pressure transducer inside the Hydraulic Control Unit (HCU) to verify the stoplamp switch status message from the PCM. When the vehicle is at rest without input from the brake pedal, the pressure transducer value should be at or close to 0 kPa (0 psi). However, due to factors such as vehicle age or minor discrepancies in manufacturing, readings may have some variability.

  This pinpoint test is intended to diagnose the following: 

• Wiring, terminals or connectors
• Stoplamp switch
• HCU 
• ABS module