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.