General Motors is addressing an issue that may cause check engine lights on 2020/2021 Diesel Silverado and Sierra pickups.  Both 3.0L and 6.6L Diesel Duramax engines could have an error related to the emission and/or exhaust fluid systems.

Technical Service Bulletin: #21-NA-07
Release Date: 1/20/2021

Vehicles Covered Under This TSB

Engines This TSB Relates To

Reported Conditions

Owners may have one more more of the following issues for no apparent reason:

  • Malfunction or MIL Light Is On
  • “Service Emission System” Error Message
  • “Service Exhaust Fluid System” Error Message
  • Some vehicles may also set a P206B (Redundant Quality Sensor Circuit Performance) error message in the Engine Control Module (ECM)

Fix For This Issue

Owners who feel that they are experiencing one or more of these issues and have a vehicle and engine that falls under this technical bulletin need to visit their dealership. This fix will be entirely covered under your new vehicle warranty.

Dealership technicians will update the Reductant Control Module calibration in the truck.