21-NA-033

Bulletin No.:
Service Bulletin
Date:
21-NA-033
August, 2022
TECHNICAL
Subject:
Malfunction Indicator Lamp (MIL) Illuminated – Multiple Transmission DTCs Set
Note: If DTC P1955 or P0867 is set, please proceed to
the latest version of PIP5797 for direction.
Brand:
Model:
Chevrolet
Corvette
Model Year:
VIN:
from
to
from
to
2020
2023
—
—
Engine:
Transmission:
—
—
Involved Region or Country
North America, Europe, Middle East, Japan, Australia/New Zealand
Condition
Some customers may comment that the MIL is illuminated.
Technicians may find one or more of the following DTCs set in the Transmission Control
Module (TCM):
P0747, P0746, P0777, P0776, P2809, P2808, P2724, P2723, P0797, P0796, P2715,
P2714, P2818, P2817, P08C5, P08C4, P27BA, P27B9, P27C2, P27C1, P27CA, P27C9,
P27D2, P27D1, P282A, P2829, P1956, P1957, P1958, P1959, P2735, P18A8, P18A9,
P2821, P2820, P187D, P187E, P2855, P2853, P2856, P2854, P0869, P0868, C2A18,
C2A19, P0844, P0841, P0849, P0846, P0874, P0871, P0879, P0876, P1946, P1947,
P1948, P1949, P194A, P1961, P194B, P194C, P194D, P194E, P073F, P074A, P074B,
P074C, P074D, P074E, P074F, P07D8, P073E, P194F and/or P1950.
Cause
This condition may be caused by an Internal transmission solenoid or switch sticking due
to debris.
Copyright 2022 General Motors LLC. All Rights Reserved.
Page 2
August, 2022
Bulletin No.: 21-NA-033
Note: If circuit diagnostics are required to determine the repair, valve/solenoid cleaning,
Service Clean, and Service Fast Learn will not help. The bulletin is targeted for
mechanical and hydraulic type issues only.
Using the GDS, perform the indicated DTC solenoid cleaning procedure based on the
DTC that set. The cleaning procedure should be performed 3 times. (If required, perform
the solenoid cleaning for each additional DTC that may have set and complete the
solenoid cleaning 3 times.) Once this is completed, perform the Service Clean Procedure
followed by Transmission Service Fast Learn. Refer to the Service Procedure section
below.
• If DTCs P194F, P1950, P0747, P0746, P0777, P0776, P2809, P2808, P2724, P2723,
P0797, P0796, P2715, P2714, P2818, P2817, P08C5, P08C4, P27BA, P27B9,
P27C2, P27C1, P27CA, P27C9, P27D2, P27D1, P282A, P2829, P1956, P1957,
P1958, P1959, and/or P2735: Perform the Valve/Solenoid clean procedure based on
the DTC that set. Next, perform the Service Clean procedure then Service Fast Learn.
⇒ If codes return, replace the MCV as necessary.
• If DTCs P18A8, P18A9, P2821, P2820, P187D and/or P187E: Perform the Valve/
Solenoid clean procedure based on the DTC that set. Next, perform the Service Clean
procedure then Service Fast Learn.
Correction
⇒ If codes return, transmission replacement may be necessary. It is
recommended to contact the GM Technical Assistance Center (TAC) prior to
ordering a transmission.
• If DTCs P2855, P2853, P2856, P2854, P0869, P0868, C2A18 and/or C2A19: Perform
the Valve/Solenoid clean procedure based on the DTC that set. Next, perform the
Service Clean procedure then Service Fast Learn.
⇒ If codes return, replace the MCV as necessary EXCEPT for DTC P0867 or
P1955 set: NO SYS PRESS is either a serious mechanical issue or
extremely low fluid level.
• If DTCs: P0844, P0841, P0849, P0846, P0874, P0871, P0879 and/or P0876: Perform
the Valve/Solenoid clean procedure based on the DTC that set. Next, perform the
Service Clean procedure then Service Fast Learn.
⇒ If no other pressure codes are present, proceed to circuit diagnostics.
• If DTCs: P1946, P1947, P1948, P1949, P194A, P194B, P194C, P194D, P194E,
P073F, P074A, P074B, P074C, P074D, P074E, P074F, P07D8 and/or P073E:
Perform Valve/Solenoid cleaning “IF” accompanied with low/high sys pressure codes.
otherwise just run Service Fast Learn. (Failure of SFL would indicate mechanical
hardware).
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
Note: Prior to performing procedure, verify the
vehicle mileage is under 12,000 km (7500 miles) or
that Dual Clutch Transmission Canister filter
maintenance has been performed. See
maintenance schedule for the Dual Clutch
Transmission Canister filter. If necessary, filter
must be changed prior to this procedure.
1. Record and clear DTCs.
2. Take the vehicle for a test drive until the
transmission reaches operating temperature.
3. Use an MDI II to access communication with the
Transmission Control module (K71) through GDS.
5721628
4. Select K71 Transmission Control Module.
Bulletin No.: 21-NA-033
August, 2022
5721578
Page 3
5721596
Important: Not all of the cleaning procedures need to
be performed. Only perform one of the cleaning
procedures that correspond with the DTC that has set.
7. Perform the indicated DTC solenoid cleaning
procedure based on the DTC set a total of 3 times.
5. Select Control Functions.
5721625
6. Select Transmission Service Cleaning Procedures.
5721588
8. Once the solenoid cleaning procedure has been
completed 3 times, select Configurations/Reset
Functions.
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August, 2022
Bulletin No.: 21-NA-033
5868273
9. Select the Hydraulic System Flush Procedure.
Note: Performing the Hydraulic System Flush
Procedure test may take approximately 8 minutes to
perform in its entirety. Disregard the current statement
below stating 30 seconds to complete.
5868173
Bulletin No.: 21-NA-033
August, 2022
Page 5
11. Take the vehicle for a test drive to verify the DTCs
do not reset.
⇒ If a DTC resets, follow Service Information
diagnosis for the DTC and replace the
component that the test result leads you to.
Parts Information
No parts are required for this repair unless further
diagnosis leads you to replacing an MCV or an SAV
assembly.
Warranty Information
For vehicles repaired under the Powertrain coverage,
use the following labor operation. Reference the
Applicable Warranties section of Investigate Vehicle
History (IVH) for coverage information.
Labor
Operation
5868170
10. Perform the Transmission Service Fast Learn.
Description
Labor Time
8481938*
Perform Solenoid Cleaning
Procedure and Fast Learn
1.0 hr
Add
Each Additional Solenoid
Clean Procedure
0.1 hr
*This is a unique Labor Operation for bulletin use only.
Version
5
Modified
Released February 12, 2021
Revised June 28, 2021 – Added a Note at beginning of Service Procedure and new GDS
information to steps 8 and 9.
Revised December 07, 2021 – Added a Note under the Subject, the 2022 Model Year,
DTC P1961 to Condition section, updated the Involved Region or Country section and
updated information under step 10 and Parts Information.
Revised December 15, 2021 – Updated the Service Procedure.
Revised July 29, 2022 – Added the 2023 Model Year, removed P1955 and P0867 from
Condition and Correction sections, changed and to or in bolded text in Correction section
and added an Important statement above the Service Procedure.
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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