Troubleshooting No Trailer Connection Error on Tekonsha P3 on 2019 Chevrolet Express Van 4500

Question:

My motorhome has a 7 way already installed and the wires under the floor mat for the controller hook up. I wired the controller plug to the apropriate wires or at least I think I did. I had a red wire w/ ws that was hot when you turned on the key hooked that to Black wire. The blue wire I hooked to the blue wire from the controller to the brakes. Then there was a smaller gauge blueish green w/ ws which became live when brake depressed. I hooked that to the red wire on the controller. Then I hooked the white wire to the last wire of the 4 which was black and very small gauge. I assumed this was the ground. Nothing happened so I ran another wire to ground and got the unit to turn on but it now has a display trailer not connected. Please tell me what I did wrong or have to do to get this to work. Thank you.

asked by: Wayne O

Expert Reply:

From what you have described, you have wired your Tekonsha P3 # 90195 correctly. On the 2019 Chevrolet Express Van the red wire with white stripe is the power, which should connect to the black wire on the brake controller wiring harness. The blue wire goes with the blue wire. The blueish green, or light blue wire is the brake signal which should connect to the red wire on the brake controller. That leaves the white wire which is the ground, and it sounds like you ran it separately since it did not work when attached to the black ground wire.

I would start by double checking that ground connection on the brake controller, make sure it is secure on a clean, bare-metal surface. Since you are getting the No Trailer Connection! error there are a few other things you can check aside from the brake controller and its wiring.

You will want to inspect the 7-way connection at the back of your vehicle as well as your trailer. Make sure there is no corrosion or debris present which could interfere with the connection resulting in the error. This is the most common problem that causes this issue. If that doesn't fix it, it is likely a ground issue. Go ahead and double check your other ground connections, including the ground for the trailer brake magnets.

From there, you can check the connection at the back of your vehicle using a circuit tester like the # PTW2993 while using the manual override. If you get a signal then you know the problem is on the trailer side. If you don't, it is on the vehicle side and it is likely you will need to run a new blue wire to the 7-way.

I have attached an installation video of the P3 on a 2019 Chevy Express for your reference. I also attached a helpful article on troubleshooting brake controller installations for your reference.

expert reply by: Robin H