SureTrack Real Fix: Harness the ABS

Anti-lock brake systems (ABS) were actually first put on American cars in the early 1970s, but they’re much more common today. Also common are problems with them as the cars age. Follow this Real Fix to see how ABS codes on this 2000 Chevrolet Malibu were diagnosed and repaired.

Vehicle
2000 Chevrolet Malibu Base 3.1L

Title
C1232, C1233 ABS light on, Replaced abs wheel speed sensor wiring harness.

Complaint
The customer states the anti-lock brake system (ABS) light is on.

Cause
Confirmed the customer’s complaint and found the ABS light was on. Connected a scan tool and found codes: C1232 – Left Front Wheel Speed Sensor Circuit Open Or Shorted and C1233 – Right Front Wheel Speed Sensor Circuit Open Or Shorted. With the scan tool connected, performed a road test, monitored the ABS wheel speed sensors and found the signal parameter from the left front and the right front ABS wheel speed sensors was not present. Raised the vehicle on a lift and inspected the left front and right front ABS wheel speed sensor connectors, terminals and wiring harnesses and found no apparent faults. Key on, back-probed the left front and the right front ABS wheel speed sensor connectors, and monitored the sensor signal frequency and amplitude with a lab scope while spinning the wheels by hand. The left front and right front ABS wheel speed sensors did not produce an observable signal or waveform. Disconnected the harness connectors for the left front and right right front ABS wheel speed sensors. Key on, used the multi-meter to measure the specified 12 Volt supply at terminal “A” of the left front and right front ABS wheel speed sensor connectors and found the 12 Volt supply was not present. Key on, used the multi-meter to back-probe the electronic brake control module (EBCM) connector terminals “A10” left front and “A8″ right front ABS wheel speed sensors and found the 12 Volt supply was present. Disconnected the EBCM connector, used the multi-meter to measure the resistance of the ABS wheel speed sensor wiring harness. Measured the resistance between terminal #A10” of the EBCM connector and terminal “A” of the left front ABS wheel speed sensor connector and found no continuity. Measured the resistance between terminal “A8” of the EBCM connector and terminal “A” of the right front ABS wheel speed sensor connector and found no continuity. The results of these tests verified the ABS wheel speed sensor wiring harness was faulty.

Correction
Replaced the ABS wheel speed sensor wiring harness cleared codes, performed a road test and verified the vehicle operated properly. The ABS light did not illuminate and no fault codes returned.