21-NA-095

Bulletin No.:
Service Bulletin
Date:
21-NA-095
January, 2023
TECHNICAL
Subject:
Malfunction Indicator Lamp (MIL) Illuminated - DTC P1488 or P24DA Set
Brand:
Model:
Cadillac
from
to
Escalade Models
2021
2023
Silverado 1500
2020
2021
2022
2022
2021
2023
2020
2021
2022
2022
2021
2023
Silverado 1500 - LTD
(RPO J21, VIN Digit
5 = W/Y)
Chevrolet
Silverado 1500 - New
(RPO J22, VIN Digit
5 = A/D)
Suburban
Tahoe
Sierra 1500
GMC
Model Year:
Sierra 1500 - Limited
(RPO J21, VIN Digit
5 = 8/9)
Sierra 1500 - New
(RPO J22, VIN Digit
5 = H/U)
Yukon Models
VIN:
from
Engine:
Transmission:
to
LM2
Involved Region or Country
North America, Uzbekistan, Russia, Middle East, Chile (West), Colombia (West),
Ecuador (West), Paraguay (West), Peru (West), Venezuela (West), Japan, Cadillac
Korea (South Korea), Thailand (ASEAN), Australia/New Zealand
Condition
Some customers may comment that the MIL is illuminated.
Some technicians may find DTC P1488 or P24DA (Particulate Matter Sensor Protection
Tube Performance) set in the Engine Control Module (ECM).
Cause
This condition can be caused by any exhaust leak, but is primarily caused by an exhaust
leak between the NOx catalytic converter and the rear exhaust pipe.
Correction
Refer to the Service Procedure.
Copyright 2023 General Motors LLC. All Rights Reserved.
Page 2
January, 2023
Bulletin No.: 21-NA-095
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
1. If required, support and disconnect the rear
exhaust pipe from any hangers.
5795155
Separate the UFSCR/Tailpipe Assembly and
discard clamp.
Note: It is extremely important that the pipes are clean
and free of rust.
2. Utilizing an abrasive cloth or equivalent, clean the
surfaces of the pipes.
Bulletin No.: 21-NA-095
January, 2023
6249341
3. Install the new graphite seal on to pipe as shown in
the graphic above.
5795194
4. Reconnect UFSCR and Tailpipe, verify for proper
alignment and insertion.
5. Install the new clamp.
⇒ Tighten clamp to 28 Y (21 lb ft).
6. If any of the exhaust hangers were disconnected,
re-secure them.
Parts Information
Causal
Part
Description
Part
Number
Qty
N/A
SEAL, EXH SYS
86806078
1
N/A
CLAMP, EX
86799823
1
Page 3
Page 4
January, 2023
Bulletin No.: 21-NA-095
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.
Labor Operation
Description
Labor Time
4088898*
Diagnostic’s and Testing
0.5 hr
Add
Install Exhaust Seal
1.0 hr
*This is a unique Labor Operation for Bulletin use only.
Version
8
Modified
Released April 22, 2021
Revised May 03, 2021 - Changed P42DA to P24DA and Changed Region Information to
North America.
Revised June 04, 2021 - Add Spider Patch information to Service Procedure and Parts
information section and Removed the Information to Allow the Tape to Overhang the Pipe
to Apply Tape to the Edge of Pipe.
Revised September 17, 2021 - Updated the Cause and Correction sections.
Revised January 18, 2022 - Add 2022 to Model Year and Added Additional Regions and
Countries.
Revised January 28, 2022 - Update Service Procedure section.
Revised March 03, 2022 - Removed 2WD from Model section.
Revised January 24, 2023 - Added 2023 to Model Year, Removed all Exhaust Tape
Installation Information and Replaced with Exhaust System Seal 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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