Preliminary Checks: Introduction

The ABS system has an Electronic Control Unit (ECU), to control major functions. The control unit accepts input signals from sensors and instantly drives actuators. It is essential that both kinds of signals are proper and stable. It is also important to check for conventional problems, such as air leaks in the booster or lines, lack of brake fluid, or other problems with the brake system.

It is much more difficult to diagnose a problem that occurs intermittently rather than continuously. Most intermittent problems are caused by poor electric connections or faulty wiring. In this case, careful checking of suspicious circuits may help prevent the replacement of good parts. A visual check only may not find the cause of the problems, so a road test should be performed.

Before performing actual checks, take just a few minutes to talk with a customer who approaches with a ABS complaint. The customer is a very good source of information on such problems, especially intermittent ones. Through the talks with the customer, find out what symptoms are present and under what conditions they occur, Start your diagnosis by looking for conventional problems first. This is one of the best ways to troubleshoot brake problems on an ABS controlled vehicle.

When a problem occurs in the ABS, the warning lamp on the instrument panel comes on. To actuate the self-diagnostic results mode, ground the self-diagnostic (check) terminal located on "Data Link Connector (DLC) for Consult". The location of the malfunction is indicated by the warning lamp flashes.