If you own a 2019 through 2020 new generation Silverado or Sierra (HD included) that has trouble keeping trailer lights on and/or flashes the lights on your truck every few seconds while hooked up to a trailer – here is how to fix it.
Technical Service Bulletin: #20-NA-198
Release Date: 12/4/2020
TSB #20-NA-198 Applies To:
- New Model 2019 & 2020 Chevrolet Silverado 1500
- New Model 2019 & 2020 GMC Sierra 1500
- 2020 Chevrolet Silverado 2500HD / 3500HD
- 2020 GMC Sierra 2500HD / 3500HD
TSB #20-NA-198 Reported Conditions
Some owners of the above pickups may report that while trailering, trailer lights may only illuminate for a few moments, then go out completely. On trucks with LED lighting, the lights may also flash once every 10 seconds while hooked up to a trailer.
TSB #20-NA-198 – Cause
Trailers with incandescent lighting may draw more current than expected or the trailer’s total current draw is above 7-8 amps. The higher current exceeds the trailer lighting module limits for current flow. That high voltage may also illuminate LED lights despite trailer theft deterrent not being active.
The trailer lighting module can only handle approximately 9 amps but a large trailer with many incandescent lights may surge to over 20 amps at startup.
TSB #20-NA-198 – Solution
The design of the system was changed in model year 2020 to incorporate an internal relay found in the Trailer Lamp Control Module. Depending on the model year of the truck, dealers can replace the control module, repin the connection harness, and/or reflash the software to change the current limits. A dealership may need to do one or all three of the above to fix the condition for your truck.
This is a dealer only solution, as new software calibrations can only been loaded using dealer service software. This is a warranty item.
Zane Merva is the Executive Editor of GM-Trucks.com and the President of the New England Motor Press Association (NEMPA). A veteran automotive journalist with over 26 years of experience, Zane is a designated ‘Car Talk’ Expert and has been a contributor to The Boston Globe. He possesses a unique evaluative perspective, having road-tested more than 2,000 vehicles across every major manufacturer. While he is a recognized authority on General Motors truck platforms—including the Silverado, Sierra, and Colorado—his expertise is grounded in decades of deep competitive analysis that few in the industry can match. His commentary has been featured by major OEMs and media outlets, including Hyundai and PR Newswire