21NA002

Bulletin No.:
Service Bulletin
Date:
21-NA-002
January, 2021
INFORMATION
Subject:
Diagnostic Tip to Diagnose Emission Reduction Fluid Tank Heater Element Exposed to
Diesel Exhaust Fluid (DEF) , Service Emission System/Service Exhaust Fluid System
Displayed on the Driver Information Center (DIC), Malfunction Indicator Lamp (MIL)
Illuminated - DTC P20BB and/or P20C3 Set
Model Year:
VIN:
Brand:
Model:
Cadillac
Escalade
2021
LM2
Silverado 1500
2020
LM2
Chevrolet
Silverado 2500HD/
3500HD
2020
L5P
Suburban
2021
Sierra 1500
2020
LM2
Sierra 2500HD/
3500HD
2020
L5P
Yukon
2021
LM2
GMC
from
to
2021
from
to
Engine:
Transmission:
LM2
Involved Region or Country
North America
Condition
Some customers may comment that the MIL is illuõminated with or without a "Service
Emission System/Service Exhaust Fluid System" message.
Some technicians may one or more of the following DTCs set in the Engine Control
Module (ECM):
• P20BB: Reductant Heater 1 Control Circuit Low Voltage
• P20C3: Reductant Heater 3 Control Circuit Low Voltage Test Status
Cause
This condition may be caused by a faulty Emission Reduction Fluid Tank heater.
Correction
Note: If the technician finds code P20BB and/or P20C3, the following procedure can be
used to identify an issue with the Emission Reduction Fluid Tank heater
The following procedure may be useful to identify if the heater element is exposed to DEF
fluid
Service Procedure
Important: Ensue that the Emission Reduction Fluid
Tank has enough fluid in it to cover the heaters before
performing the resistance measurement.
1. Turn the vehicle off.
2. Disconnect the Emission Reduction Fluid Tank
Reservoir Wire Harness.
Copyright 2021 General Motors LLC. All Rights Reserved.
Page 2
January, 2021
Bulletin No.: 21-NA-002
5701194
3. Utilizing a DVOM, measure resistance from pin 9
(1) to pin 14 (3) of the Emission Reduction
Fluid Tank.
4. Measure resistance on pin 10 (2) to pin 14 of the
Emission Reduction Fluid Tank.
• If either resistance readings are less than 10M
ohm, the heater is faulty.
• If both resistance readings are greater than
10M ohm, refer to SI for further diagnostics.
Version
1
Modified
Released January 13, 2021
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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