Something is wrong with my ABS system

Michael Mobile Technician Clinton, Utah Posted   Latest  
Case Study
Chassis
2010 Chevrolet Silverado 1500 LT 5.3L (3 LC9) 6-spd (6L80)
C1234
Abs Lamp On

A while back I went to program a ABS module on a Chevrolet Silverado. The customer stated that when checking the ABS sensor on the right rear the circuit voltage would drop during the test. There was a code for the right rear sensor signal low. He concluded that the module had a weak driver that was dropping out.

After programming we experienced the same result. He had a known good sensor which he substituted which made no effect. Since two of the three elements had been eliminated, what was left was the wiring. We did a visual inspection of the tubing and wiring. We found one wire that crosses a brake line. It had rubbed into the brake line causing a kink. The small clip that holds the wire off the line had come undone. I thought for sure the problem would be there. I had to leave but asked the shop owner to take some pictures for me.

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The shop owner opened up the wiring at the kink to check it out. No problems were found.

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Investigating further he pulled back the convoluted tubing from the wiring. There it was in a nice protected area. No evidence of how the damage happened.

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All we could figure is the wire got nicked during assembly. The bare copper was exposed to road salt and water. Chemistry did the rest. Kudos to Dave for finding the culprit.

+6
Interesting
Thanks
Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Nice find

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Patrick Diagnostician
Farmington Hills, Michigan
Patrick Default
 

Thanks for the post. I now utilize a 906 light bulb and load test ABS wires with the sensors and module disconnected from the harness. It pinpoints which wire is gangrenous when the visual inspection may not be apparent.

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Helpful
Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Mike: While I appreciate the wiring find, I'm confused on the determination that a "driver" would cause a sensor signal dropout. Thoughts? Guido

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Michael Mobile Technician
Clinton, Utah
Michael Default
 

Guido, I suppose the thought was the driver or voltage regulator was damaged. I am not sure on GM vehicles but others have used a Bias voltage in the past to do a circuit test. Maybe that was their thinking. I was just the programmer who was trying to help the shop after replacing a part that did not need replacing. -Mike

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Jimmy Analyst
Québec, Quebec
Jimmy Default
 

Would it be okay if I used this in an automotive textbook for author James Halderman? It's for educational purposes for students. I'm doing research for him and this would be of interest for him.

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