If your 2024-2026 Chevrolet Silverado HD or GMC Sierra HD is suddenly lighting up the dash like a Christmas tree, the fix might be as simple as two dirty ground connections under the hood.
General Motors has issued Technical Service Bulletin #26-NA-202 covering 2024, 2025, and 2026 Silverado 2500HD, Silverado 3500HD, Sierra 2500HD, and Sierra 3500HD trucks. The culprit: high resistance at two body harness grounds, G103A and G103B, that can throw the truck’s electrical network into chaos.
The Symptoms: Warning Lights and Communication Errors
Affected trucks can show a whole mess of problems while running, driving, or even just idling. Owners have reported multiple illuminated warning lights, a string of messages on the Driver Information Center, and CAN Bus communication errors between modules.
More concerning, the truck may lose communication with the Electronic Brake Control Module entirely. That is the module responsible for ABS and stability control functions, so this is not a “drive it until it gets worse” situation.
Technicians may find several diagnostic trouble codes stored, including DTC B1980 (No Environment Identifier Received From Brake System Control Module 1) along with communication codes U1610, U0121, U2418, U2419, U160F, U0101, U0131, U1611, and U0401.
The Cause: Two Bad Grounds Under the Hood
All of these electrical gremlins can trace back to high resistance at grounds G103A and G103B on the body wiring harness. On the HD trucks, both grounds live under the hood on the inboard side of the left body structure, right next to the X50A Engine Wiring Harness Junction Block.
When the mating surface where those grounds bolt to the body gets corroded or contaminated, resistance climbs, voltage gets flaky, and modules all over the truck start losing their minds.
The Fix: Clean the Mating Surface
The repair is refreshingly simple. Technicians clean the mating surface on the body structure where grounds G103A and G103B attach, then confirm proper system operation. No harness replacement, no module swaps, just a clean metal-to-metal connection.
Quick Reference
What HD Owners Should Do
If your Silverado HD or Sierra HD is throwing random warning lights or communication codes, mention Bulletin #26-NA-202 to your dealer’s service department and ask them to check grounds G103A and G103B before anyone starts throwing expensive parts at the problem. A five minute ground cleaning beats a misdiagnosed module replacement every time.
You can keep up with the latest service bulletins for your truck in our TSB coverage.
Dealing with mystery warning lights on your HD? Join the conversation with thousands of fellow owners in our 2020-2026 Silverado HD & Sierra HD forum.
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