Bulletin No.
: 17-NA-393
Service Bulletin Date: November, 2020
INFORMATION
Subject: Information On Poor DEF Quality Message Displayed on Driver Information Center
(DIC) and/or Malfunction Indicator Lamp (MIL) Illuminated - DTC’s P249D, P249E Set
Model Year: VIN: Engine: Transmission:
Brand: Model:
from to from to
Silverado 2500/3500 2017 2019
Chevrolet Silverado
2020 2021
2500/3500 HD - - L5P -
Sierra 2500/3500 2017 2019
GMC
Sierra 2500/3500 HD 2020 2021
Involved Region or Country North America and Israel
Some customers may comment on one or more of the following conditions:
• DEF Quality Message displayed on the DIC
• MIL illuminated
Condition
The Technician may find one or more of the following DTC’s set:
• P249D
• P249E
This vehicle is equipped with a DEF Quality sensor that is integrated into the DEF tank.
The value of this sensor can be read in the reductant data as the Reductant
Concentration. If this concentration falls below 26%, the Exhaust Fluid Quality Poor
message will be displayed on the DIC.
The NOx Catalyst Reductant-Load Adaptive Value can be found in the Reductant System
Data list in GDS2. This feature is the ECM’s way to “close the loop” on the NOx
Reduction System. The NOx Reduction System consists of the diesel exhaust fluid, DEF
dosing hardware (Emission Reduction Fluid Injector, Emission Reduction Fluid Exhaust
Front Pipe Injector Supply Pipe, Emission Reduction Fluid Tank, Emission Reduction
Fluid Supply Pump Module, and Emission Reduction Fluid Controller), and the Warm Up
NOx Catalytic Converter. The NOx Reduction System removes the NOx (Nitrogen
Oxides) from the vehicles exhaust under various conditions. The ECM measures this
reduction by looking at the NOx 1 and NOx 2 sensor readings. The ECM also looks at
other sensors to predict what the NOx reduction should be. Certain things can influence
how the system works, tolerances on sensors (Mass Airflow Sensor, Nitrogen Oxides
Sensor, Emission Reduction Fluid Injector, Exhaust Temperature Sensor, etc.), Exhaust
Information piping, Warm Up NOx Catalytic Converter brick, etc. Also intake or exhaust leaks can
impact the performance of the NOx Reduction System. Under proper conditions the
system will “adapt” when it sees an error in the predicted downstream NOx as compared
to the actual downstream sensor reading. If a large enough error is measured between
the two calculations over a time period, the NOx Catalyst Reductant-Load Adaptive Value
changes to account for this.
If the DEF injector is in tolerance, but is injecting on the low side of the spec. Eventually
the system would be under loaded (not enough DEF on the SCR) and there will be an
error between the model (or the predicted NOx 2 reading) and the measured NOx 2
sensor.
⇒ The NOx Catalyst Reductant-Load Adaptive Value will adapt to a value
larger than one, (example 1.1). So when DEF dosing is requested, it will be
multiplied by the NOx Catalyst Reductant-Load Adaptive Value factor or 1.1.
If the NOx Catalyst Reductant-Load Adaptive Value is below 0.41 or above 1.99, code
P249D or P249E will set.
Copyright 2020 General Motors LLC. All Rights Reserved.
Page 2 November, 2020 Bulletin No.: 17-NA-393
Parts Information
No parts are required for this repair.
Version 3
Modified Released December 08, 2017
Revised July 26, 2018 – Added 2019 Model Year.
Revised October 26, 2020 – Added 2020–2021 Model Years.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these
technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper WE SUPPORT VOLUNTARY
service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a
job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your TECHNICIAN
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the CERTIFICATION
information.
