SureTrack Real Fix: Loom with a Vue

Real Fixes from Mitchell 1’s SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is available at no additional cost in our ProDemand product.


Anti-lock brake system (ABS) failures are fairly common in vehicles. With spinning and moving parts in vulnerable areas of the vehicle it’s understandable that those components can fail. Follow this Real Fix to see how a code C0040 on this Saturn Vue was diagnosed and repaired.

Vehicle
2008 Saturn Vue XE 2.4L

Title
C0040, Replaced Anti-Lock Brake Wire Harness, ABS Wheel Speed Sensor

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

Cause
Connected a scan tool and found code C0040 – Right Front Wheel Speed Sensor Circuit Malfunction. With the scan tool connected performed a road test and monitored the ABS wheel speed sensors and found the signal parameter from the right front ABS wheel speed sensor was erratic and had dropouts. Raised the vehicle on a lift and inspected the right front ABS wheel speed sensor connector, terminals and wiring harness and found no faults. With the key on, used a multi-meter, back-probed the right front wheel speed sensor positive connector to check for the presence of the specified 12 Volts and found 12 Volts was present. Back-probed the right front ABS wheel speed sensor, and monitored the sensor signal with a lab scope while spinning the wheel by hand. The wheel speed sensor produces a digital square Wave signal. The electronic brake control module (EBCM) uses the frequency of the wheel speed sensor signal to determine wheel speed. As wheel RPM increases, frequency (HZ) should also increase with no drop-outs or glitches during test. The right front ABS wheel speed sensor signal and waveform observed on the the lab scope was erratic. While spinning the right front wheel and observing the lab scope signal, wiggled the ABS wiring harness and found the signal dropped out completely. Removed the left front ABS wheel speed sensor wiring harness from the body harness, used the multi-meter to measure the resistance of the wiring harness and found as the harness was wiggled there was no continuity. Replaced the right front ABS wheel speed sensor wiring harness, retested the ABS wheel speed sensor with the lab scope and found the signal observed on the lab scope was erratic. The results of these tests verified the right front ABS wheel speed sensor wiring harness and the right front ABS wheel speed sensor were faulty.

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


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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.