I brought a Tekonsha P-3 Trailer Brake Controller for my 05’ Ford F-150. I hooked the cable to OEM brake cable that came with the vehicle and installed the ISO. The device is working fine but when I toggle through the menu I get this message “No trailer connection”. I have tried with 2 different trailer with the same problem. I also changed the ISO.

What’s wrong and how can I troubleshoot it?

 

I am guessing this error code means it cannot see the trailer brakes ?

Might want to check the 7 pin trailer tow adapter, to see if the terminals are corroded.

do the stop / turn / tail lamps work ? ( asking due to trailer ground ).

 

All the lights (turn, tail and stop) are working on both trailers.

 

Does this error code means it cannot see the trailer brakes ?

Quick test, without the brake controller plugged in ( and no trailer plugged into the 7 pin adapter ) jumper the truck side of the pigtail from the red wire to the Dark blue wire.



This should put 12 V DC on the brake lead at the 7 pin adapter, to test with a meter.



Did you check Fuse # 105 ? This is the power to the brake controller for the electric brakes ( not sure what the ISO is you were talking about ).

 

I have checked the voltage at the rear pin, its works well when applying the brakes. Everything else is working too but still the device shows me no trailer connected.

 

^ You may have a bad controller then. Have you called them yet?

 

I have sent them an email last week, no response!

 

The seller from ebay and e-trailer say that I might have issues with ground. What I need to understand is if the connecter gives voltage when applying brakes doesnt mean its grounded and the wiring is okay?

 

i just ordered the same one 3 days ago....figure this out before i get mine hooked up so that i wont have to troubleshoot if i run into the same problems!

 

Okay I have been told to test the blue cable coming out from the device using a light connection, negative to ground and positive to the blue cable.

I got 0.0 on the display and when i apply the manual brakes, the light comes up. This confirms that the connection and device are working properly (correct me if i'm wrong)

So I guess there might be wiring issues with my trailers! is it my luck to have the same issue on both trailers? How can I troubleshoot it?

 

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I have the same problem. This is what I was told to do. This will test the trailer.

When I tested my trailer it showed an open circuit. I then kept the DVOM red end on the Electric Brake terminal and touched the DVOM black end to ground, and still had an open. When I touched the battery negative terminal I still had an open, so I know the break was in the blue Electric Brake terminal.

When I followed the blue wire I found a broken connection, which needed to be repaired.

 

So now I've repaired the wire, and I have a short.

I cut the wire where I made the repair and did the same test. The short is on the brakes side which probably means I have bad magnets. Now what do I do???

 

I took my trailer to a local trailer seller. They looked it over and said every thing was fine. I hooked the trailer to my truck and the brakes work great. There was no explanation as to why the brake wires test shows it to have a short??? I'm confused!

 

How did you find the short?