ANTI-LOCK BRAKE SYSTEM (ABS) 5A4-7 until there is no longer a need for the anti-lock function or until the vehicle is stopped. A slight ticking or popping noise may be heard during brake applications when the Anti-lock features is being used. When the Anti-lock feature is being used, the brake pedal may rise even as the brakes are being applied. This is also normal. Maintaining a consist force on the pedal will provide the shortest stopping distance. VDC Volts DC VAC Volts AC W/L Warning Light WSS Wheel Speed Sensor Brake Pedal Travel Vehicles equipped with the Anti-lock Brake System may be stopped by applying normal force to the brake pedal.
Although there is no need to push the pedal beyond the point where it stops or holds the vehicle, by applying more force the pedal will continue to travel toward the floor. This extra brake pedal travel is normal. General Diagnosis General Information ABS malfunction can be classified into two types, those which can be detected by the ABS warning light and those which can be detected as a vehicle abnormality by the driver. In either case, locate the fault in accordance with the “BASIC DIAGNOSTIC FLOWCHART” and repair.
Please refer to Section 5A for the diagnosis of mechanical troubles such as brake noise, brake judder (brake pedal or vehicle vibration felt when braking), uneven braking, and parking brake trouble. Acronyms and Abbreviations Several acronyms and abbreviations are commonly used throughout this section: ABS Anti-lock Brake System CKT Circuit DLC Data Link Connector DTC Diagnostic Trouble Code DVM Digital Volt Meter (High Impedance Multimeter) EHCU Electronic Hydraulic Control Unit FL Front Left FR Front Right GEN Generator HU Hydraulic Unit MV Millivolts RL Rear Left RR Rear Right RPS Revolution per Second SW Switch ABS Service Precautions Required Tools and Items:
Box Wrench Brake Fluid Special Tool Some diagnosis procedures in this section require the installation of a special tool. 5-8840-0285-0 (J-39200) High Impedance Multimeter When circuit measurements are requested, use a circuit tester with high impedance. Computer System Service Precautions The Anti-lock Brake System interfaces directly with the Electronic Hydraulic Control Unit (EHCU) which is a control computer that is similar in some regards to the Engine Control Module. These modules are designed to withstand normal current draws associated with vehicle operation. However, care must be taken to avoid overloading any of the EHCU circuits.
In testing for opens or shorts, do not ground or apply voltage to any of the circuits unless instructed to do so by the appropriate diagnostic procedure. These circuits should only be tested with a high impedance multimeter 5-8840-0285-0 (J-39200) or special tools as described in this section. Power should never be removed or applied to any control module with the ignition in the “ON” position. Before removing or connecting battery cables, fuses or connectors, always turn the ignition switch to the “OFF” position.