Base Anti-Lock Brake System (ABS) Function

The Anti-Lock Brake System (ABS) module continuously monitors brake pedal input, lateral vehicle motion and the rotational speed of each wheel. The Powertrain Control Module (PCM) sends the brake pedal switch information to the Anti-Lock Brake System (ABS) module over the High Speed Controller Area Network (HS-CAN) while the Restraints Control Module (RCM) sends lateral acceleration sensor information to the Anti-Lock Brake System (ABS) module over a private High Speed Controller Area Network (HS-CAN). Wheel speed information is retrieved by the Anti-Lock Brake System (ABS) module using 4 active wheel speed sensors, one for each wheel. When the Anti-Lock Brake System (ABS) module detects an impending wheel lock during a braking event, the Anti-Lock Brake System (ABS) module modulates brake pressure to the appropriate brake caliper(s) by opening and closing the appropriate solenoid valves inside the Hydraulic Control Unit (HCU) while the hydraulic pump motor is activated. Once the affected wheel(s) return to the desired speed, the Anti-Lock Brake System (ABS) module returns the solenoid valves in the Hydraulic Control Unit (HCU) to their normal position.

The Anti-Lock Brake System (ABS) module has 2 self-test options, one is carried out using a scan tool and the other is carried out when the Anti-Lock Brake System (ABS) is initialized (ignition ON). During either self test the Anti-Lock Brake System (ABS) module carries out a preliminary electrical check of the system sensors and activates the hydraulic pump motor for approximately one-half second. During this time, a buzzing or humming noise may be heard and a vibration may be felt in the brake pedal and is a normal condition. During the module initialized self test, the pump motor check is carried out at approximately 10 kmh (6.2 mph). Any malfunction detected in the system causes the module to set a Diagnostic Trouble Code (DTC), disable the Anti-Lock Brake System (ABS) function and send a message over the High Speed Controller Area Network (HS-CAN) to the Instrument Panel Cluster (IPC) to illuminate the Anti-Lock Brake System (ABS) warning indicator. However, the base hydraulic power-assist braking system will function normally.