Antilock Brakes / Traction Control Systems: Description and Operation

PARTICULAR PHENOMENA OF THE ANTI-LOCK BRAKING SYSTEM

Models equipped with the anti-lock braking system (ABS) may exhibit one or more of the following phenomena from time to time, but none of these are abnormal.
(1) A pulsing feeling in the brake pedal, or vibration of the body or the steering wheel, when the anti-lock braking system is activated by sudden braking or by braking on a slippery road surface. Actually, this phenomenon is an indication that the ABS is functioning normally.
(2) When the vehicle speed reaches approximately 8 km/h (5 mph) after the engine is started and the vehicle starts oft (for the first time), a whining motor noise may be heard from the engine compartment if the vehicle is traveling in a quiet place, but this noise is simply the result of a self-check being made of the ABS operation.


TROUBLESHOOTING METHODS
Problems related to the ABS can be classified into two general categories: problems in the electrical system and those in the hydraulic system. For problems in the electrical system, the diagnostic test mode is built into the electronic control unit (ECU) This mode causes the ABS warning light to illuminate as a warning to the driver. In this instance, checks can be carried out using the scan tool and an oscilloscope. Problems in the hydraulic system (poor braking, etc.) can be located in the same way as for ordinary brakes. However, it is necessary to determine whether the problem is related to ordinary brake components or to the ABS components. To make this check, use the scan tool.


HOW TO USE THE TROUBLESHOOTING FLOW CHART

(1) Following the flow chart, first refer to the illumination pattern of the ABS warning light, and next note the diagnostic trouble code and inspect the brake operation.
(2) Follow the inspection charts listed in the "Remedy" column to carry out an inspection. In each inspection chart, [Comment] and (Hint) are listed for troubleshooting reference.

NOTE: (ECU) Electronic control unit