Bulletin No.:

Service Bulletin

Date:

20-NA-066
December, 2023

TECHNICAL
Subject:

Malfunction Indicator Lamp Illuminated with One or More Glow Plug Control DTCs Set

Brand:

Model:

Chevrolet

Silverado 1500

GMC

Sierra 1500

Model Year:

VIN:

from

to

from

to

2020

2020

-

-

Engine:

Transmission:

LM2

-

Involved Region or Country

North America

Condition

Some customers may comment that the MIL is illuminated.
Some technicians may find one or more of the following DTCs set in the Glow Plug
Control Module (GPCM):
• P066A: Cylinder 1 Glow Plug Control Circuit Low Voltage
• P066B: Cylinder 1 Glow Plug Control Circuit High Voltage
• P066C: Cylinder 1 Glow Plug Control Circuit Low Voltage
• P066D: Cylinder 1 Glow Plug Control Circuit High Voltage
• P066E: Cylinder 1 Glow Plug Control Circuit Low Voltage
• P066F: Cylinder 1 Glow Plug Control Circuit High Voltage
• P0671: Cylinder 1 Glow Plug Control Circuit
• P0672: Cylinder 2 Glow Plug Control Circuit
• P0673: Cylinder 3 Glow Plug Control Circuit
• P0674: Cylinder 4 Glow Plug Control Circuit
• P0675: Cylinder 5 Glow Plug Control Circuit
• P0676: Cylinder 6 Glow Plug Control Circuit
• P067A: Cylinder 4 Glow Plug Control Circuit Low Voltage
• P067B: Cylinder 4 Glow Plug Control Circuit High Voltage
• P067C: Cylinder 5 Glow Plug Control Circuit Low Voltage
• P067D: Cylinder 5 Glow Plug Control Circuit High Voltage
• P067E: Cylinder 6 Glow Plug Control Circuit Low Voltage
• P067F: Cylinder 6 Glow Plug Control Circuit High Voltage
• P06C5: Cylinder 1 Glow Plug Incorrect
• P06C6: Cylinder 2 Glow Plug Incorrect
• P06C7: Cylinder 3 Glow Plug Incorrect
• P06C8: Cylinder 4 Glow Plug Incorrect
• P06C9: Cylinder 5 Glow Plug Incorrect
• P06CA: Cylinder 6 Glow Plug Incorrect
• P1337: Glow Plug Offset Not Learned
• P1338: Cylinder 1 Glow Plug Offset Exceeded Learning Limit
• P1339: Cylinder 2 Glow Plug Offset Exceeded Learning Limit
• P133A: Cylinder 3 Glow Plug Offset Exceeded Learning Limit
• P133B: Cylinder 4 Glow Plug Offset Exceeded Learning Limit
• P133C: Cylinder 5 Glow Plug Offset Exceeded Learning Limit
• P133D: Cylinder 6 Glow Plug Offset Exceeded Learning Limit

Copyright 2023 General Motors LLC. All Rights Reserved.

Page 2

December, 2023

Bulletin No.: 20-NA-066

Cause

This condition may be caused by a software anomaly

Correction

If you encounter a vehicle with any of the above conditions, reprogram the GPCM with
the latest available software.

Important: Service agents must comply with all
International, Federal, State, Provincial, and/or
Local laws applicable to the activities it performs
under this bulletin, including but not limited to
handling, deploying, preparing, classifying,
packaging, marking, labeling, and shipping
dangerous goods. In the event of a conflict between
the procedures set forth in this bulletin and the
laws that apply to your dealership, you must follow
those applicable laws.

Service Procedure
Caution: Before downloading the update files, be sure
the computer is connected to the internet through a
network cable (hardwired). DO NOT DOWNLOAD or
install the files wirelessly. If there is an interruption
during programming, programming failure or control
module damage may occur.
Important: Carefully read and follow the instructions
below.
• Ensure the programming tool is equipped with the
latest software and is securely connected to the
data link connector. If there is an interruption
during programming, programming failure or
control module damage may occur.
• Stable battery voltage is critical during
programming. Any fluctuation, spiking, over
voltage or loss of voltage will interrupt
programming. Install a GM Authorized
Programming Support Tool to maintain system
voltage. Refer to www.gmdesolutions.com for
further information. If not available, connect a fully
charged 12 V jumper or booster pack
disconnected from the AC voltage supply. DO
NOT connect a battery charger.
• Turn OFF or disable systems that may put a load
on the vehicles battery such as; interior lights,
exterior lights (including daytime running lights),
HVAC, radio, etc.
• Clear DTCs after programming is complete.
Clearing powertrain DTCs will set the Inspection/
Maintenance (I/M) system status indicators to NO.

Bulletin No.: 20-NA-066

December, 2023

Page 3

5431207

Important: If the Same Calibration/Software Warning
is noted on the SPS screen, select OK and follow
screen instructions. After a successful programming
event, the WCC is located in the Service Programming
System dialogue box of the SPS Summary screen. No
further action is required. Refer to the Warranty section
of the bulletin.
1. Reprogram the GPCM. Refer to K34 Glow Plug
Control Module: Programming and Setup in SI.
Modify as required (e.g., select x module from the
controller screen. Then provide step-by-step
instructions or refer to SI procedure.

Page 4

December, 2023

Bulletin No.: 20-NA-066

5431209

Important: To avoid warranty transaction rejections,
you MUST record the warranty claim code provided on
the SPS Warranty Claim Code (WCC) screen on the
job card. Refer to callout 1 above for the location of the
WCC on the SPS screen
2. Record SPS Warranty Claim Code on job card for
warranty transaction submission.

Parts Information
No parts are required for this repair.

Bulletin No.: 20-NA-066

December, 2023

Page 5

Warranty Information
For vehicles repaired under the Emission coverage,
use the following labor operation. Reference the
Applicable Warranties section of Investigate Vehicle
History (IVH) for coverage information.
Note: Warranty Coverage Codes E, E2 apply to Labor
Operation 2886728.
Labor Operation

Description

Labor Time

2886728*

Glow Plug Control Module Reprogramming with SPS for Glow
Plug Control DTCs Set

0.4 hr

*This is a unique Labor Operation for Bulletin use only.
Important: **To avoid warranty transaction rejections, carefully read and follow the instructions below:
• The SPS Warranty Claim Code must be accurately entered in the “SPS Warranty Claim Code” field of the transaction.
• When more than one Warranty Claim Code is generated for a programming event, it is required to document all Warranty
Claim Codes in the “Correction” field on the job card. Dealers must also enter one of the codes in the “SPS Warranty Claim
Code” field of the transaction, otherwise the transaction will reject. It is best practice to enter the FINAL code provided
by SPS.

Warranty Claim Code Information Retrieval
If the SPS Warranty Claim Code was not recorded on
the Job Card, the code can be retrieved in the SPS
system as follows:
1. Open TIS on the computer used to program the
vehicle.
2. Select and start SPS.
3. Select Settings.
4. Select the Warranty Claim Code tab.
The VIN, Warranty Claim Code and Date/Time will be
listed on a roster of recent programming events. If the
code is retrievable, dealers should resubmit the
transaction making sure to include the code in the SPS
Warranty Claim Code field.
Version

2

Modified

Released March 27, 2020
Revised December 06, 2023 - Added E2 to Warranty Information.

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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