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Trailer running light issue

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CCMC Enthusiast

CCMC

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My 2021 AT4 2500 Duramax is having an issue with the trailer running lights staying on with the truck off, lights off of auto, doors locked, etc. I didn't have the problem until I connected my daughters new camper trailer (incandecent running lights). And now my GN trailer with LED running lights stay on continuously. I now have an error that shows up to "check trailer wiring", I have verified that my trailer lights work as they should. I pinned out the connector on the truck trailer plug and confirmed that the running lights have 12v continuously. Is this correct? Has anyone else had this issue? And what should I do to fix this issue?

Bluedog Enthusiast

Bluedog

Posted
Posted

Delete all the trailer profiles, and set up a new one for your trailer.  Should be ok then.  The system remembers parameters from trailers connected, and likely thinks your trailer has incandescent lights.  When you connect any other trailers, either set up another profile or choose guest.

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  • 1 month later...
CCMC Enthusiast

CCMC

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Update, the dealership had to replace the trailer control module by the spare tire.

  • 10 months later...
  • 1 year later...
Steve Manych New Member

Steve Manych

Posted
Posted

I have a 2024 chev 3500, just plugged in the trailer I use all the time and now I have the same issue. I checked the 7 pin connector in the bed and on the bumper. No power at the positive pin and constant power at the running lights pin. My trailer brakes also seem to be affected. I can’t get the truck to stop using the brake controller in the truck. It feels like only one axel or one wheel is trying to brake but it’s just not enough to stop the truck unless I turn it up to 10. Checked all the fuses and everything seems ok. 

PBrown1 Enthusiast

PBrown1

Posted
Posted

I have a 2020 Silverado and had to have the Trailer Lighting Control Module replaced on the truck. This fixed the running light issue. Prior, only the brake and turn signals worked. Here is the service bulletin:

 

NHTSA Bulletin 20-NA-198

https://static.nhtsa.gov/odi/tsbs/2020/MC-10181721-9999.pdf  

2019 Model Year vehicles, equipped with U1D, use the K68 Trailer Lighting Control Module to control all trailer lighting through pulse width modulated (PWM) voltage. The Trailer Lamp Control Module has a current handling capability on the running lamp circuit of about 9 amps. On a trailer with a large number of incandescent lights, in-rush current can exceed 20 amps before it settles back to around 8-9 amps. During this inrush or "marriage" current period, the Trailer Lamp Control Module sees the current as an "overload" and goes into protection mode. 

 

This was changed for Model Year  2020 to allow 16 amps of continuous current flow by routing the current through an internal relay in the Trailer Lamp Control Module. 2019 Trucks can be modified to operate in the same way. If we use 2020 design software and re-pin the running lamps to pin 25 using the internal relay to operate the running lamps. This requires a terminated lead to be inserted into cavity 25 on the chassis harness X1 connector. Wiring connected to pin 5 on the X1 will be cut and reconnected to Pin 25. Terminal in cavity 5 will remain, be blunt cut, and sealed with a closed end duraseal splice to prevent water entering through pin 5. 

 

Software will have to be managed by TCSC. A record must exist of what trucks have been flashed and that the bulletin has been completed. Software will not work with the production configuration of wiring. This also changes the trailer connection detection flashing of LED lighting from every 10 seconds to every 42 minutes. (Connection detection will still be enabled if trailer theft deterrent is enabled)

 

 

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