Information on Poor DEF Quality Message Displayed on Driver Information Center (DIC) and/or Malfunction Indicator Lamp (MIL) Illuminated – DTCs P249D, P249E – 2016-2021 Chevrolet Colorado & GMC Canyon

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Service Bulletin Bulletin No.: 17-NA-134
Date: October, 2020
INFORMATION
Subject: Information on Poor DEF Quality Message Displayed on Driver Information Center
(DIC) and/or Malfunction Indicator Lamp (MIL) Illuminated – DTCs P249D and/or P249E
Brand: Model:
Model Year: VIN:
Engine: Transmission:
from to from to
Chevrolet Colorado
2016 2021 LWN
GMC Canyon
Involved Region or Country North America, Middle East, Israel, Palestine, GM Korea Company
Condition
Some customers may comment on one or more of the following conditions:
• DEF Quality Message displayed on the DIC
• MIL illuminated
The technician may find one or more of the following DTCs set:
• P249D
• P249E
Information
Important: Starting in 2019, vehicles now use a DEF quality sensor that is in the DEF
tank. The DEF quality sensor is the only thing that turns on the Exhaust Quality Poor
message and not the NOx Catalyst Reductant-Load Adaptive Value.
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 selective
catalyst reduction system (SCR system). The SCR 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
SCR. The SCR 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 piping, SCR brick, etc. Also intake
or exhaust leaks can impact the performance of the SCR 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 NOx2
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 reaches 1.45, it will turn on the
Exhaust Fluid Quality Poor message.
If the NOx Catalyst Reductant-Load Adaptive Value is below 0.4 or above 1.7, code
P249D or P249E will set.
Page 2 October, 2020 Bulletin No.: 17-NA-134
Parts Information
No parts are required for this repair.
Version 4
Modified
Released April 21, 2017
Revised July 25, 2018 – Added 2018-2019 to Model Years.
Revised July 29, 2019 – Added the Important statement in the information section and
updated model year to 2020.
Revised October 16, 2020 – Added 2021 Model Year.
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
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
vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.
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