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sprinkles08
sprinkles08, ASE Certified Technician
Category: Chevy
Satisfied Customers: 21570
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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Second opinion] - 2009 Silverado 2500 HD 6.0 Gas 2 days ago

Customer Question

Second opinion] - 2009 Silverado 2500 HD 6.0 Gas2 days ago I replaced the front left caliper and the master cylinder. After I did so the ABS light came on. The brakes feel fine after bleeding them, but I considered that there may be air trapped inside the ABS control module.
I took the truck to a local mechanic who put it on a computer. The computer read "unable to communicate." He tested the harness and found that it was working correctly, then checked the grounds and came to the conclusion that the module must be bad.
I found it odd for it to go out right after doing this simple repair work. Could the problem lie elsewhere? Perhaps brake fluid on wiring around the master cylinder? Or would this be a correct diagnosis?
The truck also has a message stating to check the trailer brake system. I am unsure that the 2 are related.
The truck is not showing any codes
Submitted: 3 months ago.
Category: Chevy
Customer: replied 3 months ago.
I forgot to mention the service trailer system indicator has been on for a couple of weeks. Way before I started having the ABS problem
Expert:  sprinkles08 replied 3 months ago.

Hello and welcome to JustAnswer!

The ABS light will come on if the module sets a fault code or if it isn't communicating with the instrument cluster. If the scan tool used was truly capable of communicating with your ABS module and would not then the module is not awake. If it's power and ground feeds were tested properly along with the bus communication circuits and no problems were found then the module needs to be replaced.