The Anti-lock-Brake System (ABS) module receives wheel speed readings from each wheel speed sensor and processes this information to determine if an ABS event is necessary. The wheel speed sensor electrically senses each tooth of the wheel speed sensor ring as it passes through the wheel speed sensor magnetic field.
The ABS module continuously monitors and compares the rotational speed of each wheel and, when it detects an impending wheel lock, modulates brake pressure to the appropriate brake caliper. This is accomplished by triggering the Hydraulic Control Unit (HCU) to open and close the appropriate solenoid valves. Once the affected wheel returns to normal speed, the ABS module returns the solenoid valves to their normal position, and normal (base) braking resumes.
The ABS module is self-monitoring. When the ignition switch is turned to the RUN position, the ABS module will do a preliminary electrical check, and at approximately 20 km/h (12 mph) the pump motor is turned on for approximately one half-second. Any malfunction of the ABS will cause the ABS to shut off and the yellow anti-lock brake warning indicator to illuminate. Normal power assisted braking, however, remains.
- Before servicing the vehicle, refer to the Precautions section.
Visually inspect for obvious signs of mechanical and electrical damage.
If the fault is not visually evident, connect the diagnostic tool to the Data Link Connector (DLC) located beneath the instrument panel and select the vehicle to be tested from the diagnostic tool menu. If the diagnostic tool does not communicate with the vehicle:
check that the program card is correctly installed.
- If the diagnostic tool still does not communicate with the vehicle, refer to the diagnostic tool manual.
Carry out the DATA LINK DIAGNOSTIC TEST. If the diagnostic tool responds with:
CKT914, CKT915, or CKT70 = ALL ECUS NO RESP/NOT EQUIP,
If the DTCs retrieved are related to the concern, go to the Anti-Lock Brake System (ABS) Module Diagnostic Trouble Code (DTC) below to continue diagnostics:
B1342: ECU is Defective