Own a new Chevrolet Corvette, Suburban or Tahoe, GMC Yukon or Yukon XL, or a Cadillac Escalade with a random check engine light or malfunction indicator lamp (MIL)? It could be an easy fix.
Technical Service Bulletin: #20-NA-123
Release Date: 11/13/2020
TSB #20-NA-123 Applies To:
- 2021 Chevrolet Tahoe / Suburban
- 2020 Chevrolet Corvette
- 2021 GMC Yukon / Yukon XL / Yukon Denali
- 2021 Cadillac Escalade
- 2020 Cadillac CT4 & CT5
TSB #20-NA-123 Reported Conditions
The “Check Engine Light” or Malfunction Indicator Lamp (MIL) will be on and the following trouble codes may be found.
- U1961 – Control Module Security Hardware Internal Malunction
- U1983 – Serial Data Gateway Module Security Hardware Internal Malfunction
TSB #20-NA-123 – Cause
“This condition is caused by not clearing DTCs and also allowing a sleep cycle after programming or serial data authentication configuration. ”
GM-Trucks.com’s take on this is you may find this problem after visiting a dealership where a technician may have connected your vehicle to a computer for diagnosis, software upgrade, or “authentication” during a repair. Or you are an enthusiast and have connected to or been modifying your vehicle’s computer in some way.
TSB #20-NA-123 – Solution
Clear vehicle DTCs and then allow the vehicle to go into sleep mode. This is something a dealership technician can do. This is also easily done by an educated enthusiast with the proper tools at home, if you are so inclined.
To get a vehicle into sleep mode, lock the doors and walk away. Let the vehicle sit for approximately 10-15 minutes before approaching the vehicle with a fob or unlocking the vehicle with a fob.
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