2009 GMC Acadia LED Turn Signals Operate Erratically After Installing OEM Trailer Wiring

Published 11/12/2014

Question:

I have a 2009 GMC Acadia that has LED tail lights and did NOT come with a factory tow package. I installed a standard GMC aftermarket 4-pin wiring harness and hooked up my trailer, which has standard incandescent lights, and as long as the trailer is connected, the Acadia turn signals operate erratically. Sometimes they flash properly, sometimes they dont flash at all, and sometimes both turn signals flash simultaneously. Could this be due to the fact that the trailer has incandescent lighting Ive checked and re-terminated all of the wiring on the trailer while the Acadia has LED ? If so is there a solution other than changing all of the lights on the trailer to LED and never towing a trailer without LED lights ?

asked by: Shawn

Expert Reply:

I have not heard of this issue before on an OEM part installed on a vehicle. Usually if this happens it is on the trailer and is usually a ground problem. I am not sure how the OEM harness installs but if it has its own ground wire then make sure it is attached to a clean bare metal surface. No paint or undercoating can be present. Also, it really should be grounded to its own location and not share a common ground with other electrical devices.

It is possible that the trailer lights are overdrawing the vehicles electrical system. If that is the case then switching the trailer to LED lights would be the way to go. You would have to check with GM to determine what the capacity of that OEM system is and compare that to the amperage draw of the trailer lights.

And finally, it could also be that you need to install a heavy duty flasher on the vehicle if yours is so equipped. Some newer vehicles have the flasher controlled more through the computer. You could ask a GM dealer if there is a heavy duty flasher that will fit your 2009 GMC Acadia. I have included some links to the right that might also help troubleshoot.

expert reply by: Michael H