Antilock brake system (ABS) diagnosis is following a familiar pattern. That is, the customer's complaint is much more likely to be caused by a basic brake problem than an actual ABS failure. This is not the first time a fascination with new technology has turned into a costly distraction. When computerized engine control systems appeared, for example, many technicians immediately blamed all driveability complaints on those systems. However, sharper techs soon learned that a computer-control system performs only as well as the engine to which it's connected. Not only do basic engine problems still make the vehicle run poorly, they may trigger false fault codes in the computer. Therefore, routine engine repairs-not electronic hocus pocus-often corrects the customer's complaint.
Every brake service source we contacted said that same pattern repeatedly occurs with ABS systems. That is, an ABS-equipped vehicle has a brake-related symptom of some kind and/or the ABS warning light on the dashboard is on. The mere presence of the ABS system or a warning light throws many technicians headlong into detailed ABS diagnostics.
After wasting considerable time and effort-and possibly some new parts-the tech discovers the real cause of the customer's complaint is a basic brake problem. For all its sophistication, ABS is only as good as the brake system on which it's mounted.
This special service section focuses on commonly overlooked basic brake problems, especially those that affect ABS. It also reviews some often forgotten but valuable diagnostic techniques.