Brakes and Traction Control: Testing and Inspection

Brake Diagnosis Chart:

ROAD TEST CONDITIONS
If a road test is required to diagnose a brake complaint, the car should be driven on roads which are dry, clean, level and reasonably smooth. A true test of brake performance cannot be made if the road is wet, greasy or covered with loose dirt so that all tires do not grip the road equally. Testing will also be adversely affected if the roadway is crowned so as to throw weight of the car toward one side or if the roadway is so rough that the wheels tend to bounce.


PROCEDURE
Test the brakes at different car speeds with both light and heavy pedal pressure. The Antilock Brake System is designed to engage the antilock mode anytime that a wheel locking tendency is detected by the Electronic Brake/Traction Control Module (EBTCM); as a result, application of heavy pedal pressures during testing may cause the ABS to cycle. This is indicated by a rapid pulsation in the brake pedal, accompanied by a popping or ticking noise from the hydraulic unit. During heavy antilock braking on dry pavement, the tires will make intermittent "chirping" noises as they approach lock-up. This effect is less pronounced on wet or icy pavement, or on dirt or gravel roads. Before road testing to diagnose ABS-related complaints, see the inspection procedures in Antilock Brake System and Traction Control System.