Brake Diagnostic Scan Tools

A mechanic using two OBD 2 scan tools.

OEM and most aftermarket brake diagnostic scan tools offer the essential functions of reading and clearing codes, enhanced datastream, recording multiple data streams, and commanding on or activating brake system relays, lights, and actuators. In addition, bidirectional scan tools provide two-way communication between the scanner and the modules on the CAN.

Brake Warning Lights

If the red brake warning light on the instrument panel is on, check the parking brake and master cylinder reservoir level. The parking brake may be left partially engaged, and the brake fluid level in the reservoir drops as the brake pads wear. The brake fluid level sensor notifies the control module of a low brake fluid level.

A mechanic using a bidirectional scan tool for diagnosis.

If the parking brake warning light is inoperative with the parking brake engaged, rule out the bulb by activating and testing it with the scan tool's bidirectional function.

Electronic Parking Brakes

Electric parking brake switch.

Vehicles with electronic parking brakes automatically engage the parking brake when the transmission is in PARK or parked on an incline (Hill-holding). Some have a central motor that replaces the hand lever that pulls and releases the parking brake cable.

Caliper-mounted brake actuator.

Most modern electric parking brakes have actuators bolted to special rear calipers that apply the parking brake when powered. The electronic parking brake module EPBM controls the driver input and actuators from different brake and stability control sensor inputs on the CAN. Use the in-dash navigation or a bidirectional scan tool to command the system to retract the parking brake to install new rear brake pads.

ABS Brake Bleed Tool

ABS Modulator Valve Assembly

Manufacturers require bleeding air from the brake system after replacing specific components. Air is compressible and results in a spongy brake pedal. A dedicated brake or OBD II scan tool that includes EPB/ABS auto bleed functions may be required to bleed air from the hydraulic actuator and system.