What Brake Controller Install Harness for 2004 GMC Sierra 2500HD
Updated 02/03/2026 | Published 06/28/2024
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Question:
I just ordered 90195 with the 3015-P harness for my 2004 GMC 2500HD. I removed my old control and installed the new one but it has no power. When I removed the old control I noticed the colors of the wires to the old plug are not in the same spot as the new harness. Also there is a red wire that ran to the old control that was spliced in to the old harness? Could that be the power? I assumed the power went directly to the fuse panel but possibly not. Is there a diagram showing what each wire is?
asked by: Todd
Expert Reply:
Hey Todd, so the correct Tekonsha brake controller install harness for a P3 part # 90195 and your 2004 GMC Sierra is the part # 3015-P but I wonder if someone used the 3025-P style on your truck and did some rewiring of the junction box or something otherwise odd.
The other thing to check is to make sure the connections under the hood of your truck are made which are needed to activate the brake controller wiring. See attached link if you scroll
Jameson C.
2/3/2026
Hey Todd, what ended up happening with the P3 brake controller and the 3015-P harness on your GMC? Were you able to get power to the controller after checking those under-hood connections? Your update could make it easier for the next person running into the same wiring issue.