2020 Sierra 2500 HD Denali No power to trailer lights

[freekie]

2020 Sierra 2500 HD Denali.  12800 Miles. VIN 1GT49REY8LF257046  No Trailer lights at all.  No Power to the 7 Blade connector.

 

When I hook up the trailer and connect the 7-pin adapter to  trailing wiring harness, I get no lights, and the Infotainment System shows "No Trailer Detected".   I have checked all Fuses under the hood and all are good.  I have tested 2 trailers.  Both trailers work on a different vehicle but not on this truck.  1 Trailer is Brand new 2022.

 

Truck purchased from Jim Cook Chevrolet 1075 N Main St, Marion, NC 28752

 

Can you assist me with this issue?

 

Jim

[gemarsh]

16 hours ago, freekie said:

2020 Sierra 2500 HD Denali.  12800 Miles. VIN 1GT49REY8LF257046  No Trailer lights at all.  No Power to the 7 Blade connector.

 

When I hook up the trailer and connect the 7-pin adapter to  trailing wiring harness, I get no lights, and the Infotainment System shows "No Trailer Detected".   I have checked all Fuses under the hood and all are good.  I have tested 2 trailers.  Both trailers work on a different vehicle but not on this truck.  1 Trailer is Brand new 2022.

 

Truck purchased from Jim Cook Chevrolet 1075 N Main St, Marion, NC 28752

 

Can you assist me with this issue?

 

Jim

 

 

Warranty should still be good.

[freekie]

Warranty is good only there backed up for 6 to 8 weeks

[Mic_]

ANY dealer CAN service...try another less busy ?

 

preventative...have you verified all fuses under hood/under dash / and side kick panels??

 

else could be a trailer lighting control module

[freekie]

I checked all the fuses and they all seem fine. 6 to 8 weeks is the less busy dealer .  I get the constant 12vdc at the plug but nothing else works.

[bill3232]

I have a GMC Sierra 2500 HD loaded. We haul our horses back and forth from Ct. to S. Carolina thru the mountains of Penn. and the Smokies  (995 mi.)  I kept getting "no trailer connected" fault like you. I talked a dealer in Ct. and (she was extra nice) sent me a service bulletin #21-NA-155 ( I uploaded the file). As the bulletin stated the OEM tuck side plug is made by Pollak and for proper fit use a Pollak Heavy Duity 7 pin 12-706 or 12-702 trailer side plug. My trailer plug was in perfect condition, no corrosion or damage but I wanted to stop this problem and was ready. It's to dam stressful to have problems on the road towing horses. I ordered the Pollak trailer side plug ( $13.) installed it. I hauled the horses to and from S.C. with no faults at all. I do have to say the Pollak plug fits nice and tight. While I was at it I installed 10' of new 7 strand wire back to the junction box in the trailer. 

 

 

trailer.pdf

[freekie]

Thanks.  Cant hurt to give it a shot

 

[Sean Pierson]

I had the same problem, finally resolved with a Dexter adapter - apparently the truck has problems with not registering some LEDs and won’t power a light it doesn’t sense (not enough resistance)

[freekie]

Just got it back from the dealer.  The Trailer Control Module was bad.  They replaced it and all is good now.