#21-NA-033: Malfunction Indicator Lamp (MIL) Illuminated - Multiple Transmission DTCs

[c4c5specialist]

Chevrolet Corvette 2020 2021

Condition

Some customers may comment that the MIL is illuminated.

Some 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, P1955, 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, P0867, C2A18, C2A19, P0844, P0841, P0849, P0846, P0874, P0871, P0879,P0876, P1946, P1947, P1948, P1949, P194A, 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.


Correction


Note: If circuit diagnostics are required to determine the repair, valve/solenoid cleaning, Service Clean, and Service Fast Learnwill 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 shouldbe performed 3 times. (If required, perform the solenoid cleaning for each additional DTC that may have set and complete thesolenoid cleaning 3 times.) Once this is completed, perform the Service Clean Procedure followed by Transmission Service FastLearn. Refer to the Service Procedure section below.
•If DTCs P194F, P1950, P0747, P0746, P0777, P0776, P2809, P2808, P2724, P2723, P1955, 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 ServiceFast Learn.
⇒ If codes return, replace the valve body 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.
⇒ 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, P0867, C2A18 and/or C2A19: Perform the Valve/Solenoid clean procedure basedon the DTC that set. Next, perform the Service Clean procedure then Service Fast Learn.
⇒ If codes return, replace the valve body as necessary EXCEPT for DTC P0867 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 onthe 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, P07D8and/or P073E: Perform Valve/Solenoid cleaning “IF” accompanied with low/high sys pressure codes. otherwise just run ServiceFast Learn. (Failure of SFL would indicate mechanical hardware).

[JB]

Hopefully not too many of us will be affected.

Thanks for posting up.