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08 silverado 3500 has no connection to trailer brakes (all…

08 silverado 3500 has no...
08 silverado 3500 has no connection to trailer brakes (all lights work fine) and service trailer brake message. i replaced the relay, ITBC, and dash controller circuit board. no improvements
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Answered in 5 minutes by:
3/21/2018
Jerry Newton
Jerry Newton, GMC Technician
Category: GM
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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This has scan tool diagnostics, have you retrieved trouble codes yet?

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Customer reply replied 5 months ago
no codes

Does your scan tool communicate with the trailer brake module?

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Customer reply replied 5 months ago
no

OK, so there probably are codes, but you can't access them.

This is a tough diagnosis without the trouble code to tell us what the computer is complaining about, a lot tougher than it has to be. I can give you a schematic, and you can trace the brake wiring, power and ground circuits, things like that, but without knowing exactly why the TBC is turning on that message, it's all just a crapshoot, and hoping to come up with the right answer by accident.

$50 worth of diagnosis time at a local repair shop would have saved you many times that much money already, since you've replaced parts that didn't need to be replaced. If this were in my shop, I wouldn't attempt a diagnosis on this without at least knowing the trouble code, and there is other really pertinent data that can be gained from a good scan tool.

I'll give you the schematic if you like, but I really recommend having this looked at by someone with the right scan tool to get these answers.

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Customer reply replied 5 months ago
getting a new scan tool tomorrow and will see if codes pop up. thanks

You're welcome, let me know what you find there, and I can get you all the resources you need.

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Please take a moment to rate my answers by clicking on the stars at the top of the page, that's how I get compensated. If you need more help, just let me know, I am happy to follow up.

Jerry Newton
Jerry Newton, GMC Technician
Category: GM
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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