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Factory Brake Controller Does Not Recognize Trailer and Does Not Send Power  

Question:

Hi I have a 2009 chevy 3500 came with towing package, At first trailer connected message was coming on and off with check trailer wires on the message screen now nothing comes up when trailer is connected butt all lights work and signals. I pulled out the test light and the blue wire on the truck plug the light comes on only for a split second with or without the brake peddle pressed and doesnt do it again unless I unhook the tester than hook it again will it light for that split second no matter what I connect and check still no message that the trailer is connected any ideas

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Helpful Expert Reply:

When you are testing the blue wire, are you testing the wire with the trailer connected or using a tester with an light bulb like part # PTW2993? We have found that circuit testers do not always provide enough of a load for the OEM brake controllers to think a trailer is connected, so the brake controller does not respond correctly.

I recommend plugging the trailer in to the truck and probe the blue wire while someone holds the manual override down. You should see full power on that wire. The best way to test the brake controller is with the manual override because GM uses a proportional brake controller, so the brake pedal will only send a small amount of power, then die down because the brake controller does not sense the truck braking.

If you do not see full power, then there are a few potential problems. There could be a short somewhere on the truck or trailer, a weak ground, bad brake magnets or a problem with the brake controller.

Be sure to check for corrosion on your trailer connectors and check the main trailer ground and the grounds for the brake magnets. If the grounds look good, check the electric brake output wire on the trailer and as much as you can on the truck looking for any pinched, frayed or damaged sections of wire that could be causing a short. If the wiring checks out, then the brake magnets could be bad. If you look at the magnets and see abnormal wear or the copper windings, then I would change the brake magnets. I have also attached a help article that explains how to test your brake magnets.

If the wiring, brake magnets and grounds look okay, then the problem may be with the brake controller itself. you could either take the truck to a GM dealer to have them inspect the controller or install an aftermarket brake controller like the Prodigy P2, # 90885. I have attached a tech bulletin that explains how to install an aftermarket brake controller on a GM truck with the factory controller for you to check out if you are interested.

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John H

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