Troubleshooting Vehicle that Won't Start After Brake Controller Install

Question:

I bought a new p3 controller and plug in wire. Truck has the two package. After installing the p3, when I try to start the truck the dash lights come on but starter motor does not ingage, also the brake peddle seems hard.

asked by: Steve J

Expert Reply:

Without knowing what truck you have it's hard for me to know if you have the correct harness. I will say that the problems you are describing are unlike any problems we have ever seen from installing a brake controller. If removing the brake controller makes the problems go away then I would strongly recommend you do so until you figure out why this problem is occurring. Make sure you have your truck shifted into park or neutral before you attempt to start it. You may have moved the shifter to gain access for mounting the brake controller and forgot to put it back to park.

The brake pedal seeming hard can unrelated, if you pump the brakes a few times with the vehicle off the brakes will get hard to press.

I attached an FAQ article on brake controller installs for you to check out as well.

expert reply by: Jameson C

J. S.

5/3/2024

I am having the same issue. My truck is a GMC 3500 HD and the model year is a 2012. Do you have any suggestions or insight?

Jameson C.

5/3/2024

@JS First try removing the brake controller and see if the problem goes away. We never heard back from this guy to let us know what it was.

J. S.

5/5/2024

@JamesonC Thanks. I unplugged the controller. I replaced the crank/run relay. It ran for a bit and now does not start. Could it be a wiring issue with my wire harness? Or a fuse issue? I will try cutting the controller wires and see what happens.