SureTrack Real Fix: Express Brake Issues

Anti-lock brake system harnesses and and sensors really take a beating in normal use and are common failure points. Follow this Real Fix to see how ABS codes on this 2006 Chevrolet Chevy Express were diagnosed and repaired.

Vehicle
2006 Chevrolet Chevy Express G3500 6.0L

Title
C0040, C0045, Replaced ABS Wheel Speed Sensor Wiring Harness, Wheel Hub Assembly

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

Cause
Connected a scan tool and found codes: C0040 – Right Front Wheel Speed Sensor Circuit and C0045 – Left Rear Wheel Speed Sensor Circuit. With the scan tool connected, performed a road test, monitored the ABS wheel speed sensors and found the signal parameter from the right front ABS wheel speed sensor was erratic and the signal parameter from the left rear ABS wheel speed sensor was not present. Raised the vehicle on a lift and inspected the right front ABS wheel speed sensor connector, terminals and wiring harness and found no apparent faults. Key on, back-probed the right front ABS wheel speed sensor, monitored the sensor signal frequency and amplitude with a lab scope while spinning the wheel by hand. The right front ABS wheel speed sensor produced an erratic signal and waveform. While spinning the right front wheel noticed the wheel bearing was noisy. Removed the right front wheel, used a dial indicator to measure the specified maximum 0.005 inch end play of the wheel hub and found the measurement exceeded specifications. Key on, used a multi-meter to check for the presence of the specified 12 Volts and less than 100mV ground at the right front ABS wheel speed sensor harness connector and found both were present. Right front ABS wheel speed sensor disconnected, used the multi-meter to measure the specified 700 to 10,000 Ohms resistance of the right front ABS wheel speed sensor and found the measured resistance was out of specifications. The ABS wheel speed sensor and wheel bearing is integrated into the wheel hub assembly and is replaced as an entire unit. Key on, used the lab scope to monitor the signal and waveform of the left rear ABS wheel speed sensor while spinning the wheel and found no signal or waveform was present. Key on, disconnected the connector for the left rear ABS wheel speed sensor, used the multi-meter to measure the specified 12 Volt supply at the harness connector and found the 12 Volt supply was not present. With the multi-meter still connected manipulated the wiring harness for the left rear ABS wheel speed sensor and found the 12 Volt supply intermittently was present. Opened the wiring harness insulation and found the wires were broken inside the left rear ABS wheel speed sensor wiring harness. The ABS wheel speed sensor and wheel bearing is integrated into the wheel hub assembly and is replaced as an entire unit. These test results verified the left rear ABS wheel speed sensor wiring harness and the right front wheel hub assembly were faulty.

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