Attention diesel GM truck and SUV owners! General Motors has released a crucial service bulletin addressing specific issues related to the Malfunction Indicator Lamp (MIL) and Diesel Exhaust Fluid (DEF) level sensor. If you are driving any of the affected models listed below, check out if you have any symptoms that match those covered by this TSB.

Affected Vehicles:

All models have a 3.0L Duramax (LM2) or 6.6L Duramax (L5P) Diesel Engine:

  • Cadillac Escalade Models (2021-2024)
  • Chevrolet Silverado 1500, 2500HD/3500HD, and Suburban (2020-2024)
  • Chevrolet Tahoe (2021-2024)
  • GMC Sierra 1500, 2500HD/3500HD (2020-2024)
  • GMC Yukon Models (2021-2024)
  • Chevrolet Silverado 1500 LTD (Specific VINs)
  • Chevrolet Silverado 1500 New (Specific VINs)
  • GMC Sierra 1500 Limited (Specific VINs)
  • GMC Sierra 1500 New (Specific VINs)


Owners of the affected vehicles may experience one or more of the following issues:

  • Illumination of the Malfunction Indicator Lamp (MIL)
  • Display of “Service Emission System” and/or “DEF Level Low” messages on the Driver Information Center (DIC)
  • Incorrect DEF level sensor readings
  • Erratic behavior of the DEF level sensor
  • DEF level sensor getting stuck


GM Engineers have determined that these issues may be attributed to a software anomaly within the vehicle’s system.

Repair Procedure:

To address these issues, it is crucial for vehicle owners to take their vehicle to an authorized GM dealer. The dealer will perform the following steps:

  1. Update the K115 Reductant Control Module with the latest calibration.
  2. Ensure the DEF tank level reads at least 35% in GDS2. If not, add one gallon of Diesel Exhaust Fluid to the tank and perform a Reductant Fluid Tank Level Reset using GDS2.
  3. Fill the remainder of the Emission Reductant Fluid Tank with Diesel Exhaust Fluid.
  4. Clear any Diagnostic Trouble Codes (DTCs) after programming is complete.
  5. Please note that no parts are required for this repair, and the labor time is estimated at 0.9 hours.

TSB / Service Document Number:

Originally Issued in 2022 but reissued in October of 2023

Important Reminder:
This service bulletin is intended for use by professional technicians with the necessary equipment, tools, and training. Vehicle owners are strongly advised to contact their GM dealer to schedule an appointment for this essential service update. Ignoring these symptoms could lead to suboptimal vehicle performance and should be addressed promptly to ensure the longevity and reliability of your GM vehicle.