Electric Mirrors don't work

[Gary Baker]

Being new to the forum world I hope I'm doing this right.

I recently purchased a 2015 GMC 2500 HD used with a newly installed CM flatbed.

80000 Primarily highway miles and very clean and well kept.

Purchased from a dealership so previous owner history is not available due to privacy laws.

Everything on this truck works like new except a few functions of the electric Mirrors.

 They are manual extend and manual fold and both upper panes adjust fine.

The problem is that the turn signals do not flash in the mirror "dots", the Amber clearance lights do not come on and the rear facing white lights do not come on with the box lights.

No way of knowing if the heated part works being it's summer.

Trying to search the owners manual for fuse information was a bit of a challenge so I tested all fuses for power on both sides and all that have any power have power on both sides in all 3 panels.

I thinking that one of the relays or circuit breakers must have failed and are not labeled for function that I can access.

 Fuse labeled htd mir has no power on either side.

 Any help would be greatly appreciated!

 GB

[CadillacLuke24]

Is the harness pinched between the door and the cab?

[silveradosid]

the mirrors were probably not the original mirrors. being a 2015 it might be missing the wiring circuits for the lights, the best thing to do is to get a hold of Phil at harnessdoctor.com

[Lsgun1]

I agree with the above post. Could be aftermarket swapped on and not wired or factory upgrades swapped on and not wired. You'll have to check the harness to see if it's pinned for those functions.

[Gary Baker]

8 hours ago, Lsgun1 said:

I agree with the above post. Could be aftermarket swapped on and not wired or factory upgrades swapped on and not wired. You'll have to check the harness to see if it's pinned for those functions.

Build codes claim it had tow mirrors

[Lsgun1]

It would be really odd for both mirrors to lose those functions. What module actually controls them? I would think there would be another relay for the signals in the mirrors unless it just runs off the turn signal relay? Have you tried checking for power/ground with the directional on to see if it cuts in and out?

[Gary Baker]

I would really like to find someone who knows which relay powers these functions but it seems they are scarce.

Operators manual is no help as is the local dealer.

He just wants me to schedule an appointment for it.

Seem as though someone one here would know but figuring out how to reach them is my biggest issue.

[Gary Baker]

On 8/17/2020 at 4:09 AM, silveradosid said:

the mirrors were probably not the original mirrors. being a 2015 it might be missing the wiring circuits for the lights, the best thing to do is to get a hold of Phil at harnessdoctor.com

You were correct!

The mirrors from the factory wee code DL8 and ones currently on it are DPN.

Door harnesses or adaptors required!

[silveradosid]

when i did my mirrors on my 2014 i made my own harnesses and it took me 9 hours start to finish. you can get all the info from this post 

if i was to do it again i would get the harnesses from pgamboa