Multiple Transmission DTCs Set

Some 2020-2021 Corvette models may have multiple DTCs set in the Transmission Control Module (TCM). The DTCs may be caused by an internal transmission solenoid or switch sticking due to debris in the DCT TR-9080 transmission (RPO M1L). (Fig. 20) Based on the DTCs that are set, GDS2 should be used to perform the appropriate solenoid cleaning procedure.

 

Fig. 20

 

The cleaning procedure should be performed three times. If required, perform the solenoid cleaning for each additional DTC that may have set and complete the solenoid cleaning three times. Once completed, it will be necessary to perform the Service Clean Procedure followed by the Transmission Service Fast Learn.

TIP: The cleaning procedure is targeted for mechanical and hydraulic conditions. If circuit diagnostics are required to determine the repair, valve/solenoid cleaning, Service Clean, and the Service Fast Learn will not address the issue.

 

Cleaning Procedures Based on DTCs Set

Use GDS2 to perform the following cleaning procedures for the DTCs set in the TCM.

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 are set:

  • Perform the system cleaning procedure based on the DTC that set.
  • Next, perform the Service Clean Procedure and then the Service Fast Learn.
  • If DTCs return, replace the valve body as necessary.

 

If DTCs P18A8, P18A9, P2821, P2820, P187D and/or P187E are set:

  • Perform the system cleaning clean procedure based on the DTC that set.
  • Next, perform the Service Clean Procedure and then the Service Fast Learn.
  • If DTCs return, transmission replacement may be necessary. Contact the GM Technical Assistance Center (TAC) for more information prior to ordering a transmission.

 

If DTCs P2855, P2853, P2856, P2854, P0869, P0868, P0867, C2A18 and/or C2A19 are set:

  • Perform the system cleaning clean procedure based on the DTC that set.
  • Next, perform the Service Clean Procedure and then the Service Fast Learn.
  • If DTCs return, replace the valve body as necessary, except if DTC P0867 (Transmission Fluid Pressure Performance) is set. No system pressure is either a serious mechanical issue or extremely low fluid level.

 

If DTCs: P0844, P0841, P0849, P0846, P0874, P0871, P0879 and/or P0876 are set:

  • Perform the system cleaning clean procedure based on the DTC that set.
  • Next, perform the Service Clean Procedure and then Service Fast Learn.
  • If no other pressure DTCs 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 are set:

  • Perform system cleaning cleaning IF accompanied with low/high system pressure codes; otherwise, perform the Service Fast Learn.
  • Failure of the Service Fast Learn would indicate a mechanical hardware condition.

 

Service Procedures

After recording and clearing the DTCs, and with the transmission at operating temperature, use GDS2 to perform the Transmission Service Cleaning Procedures. (Fig. 21)

 

Fig. 21

 

Select the transmission cleaning services that correspond with the DTCs set. (Fig. 22) Not all cleaning procedures listed need to be performed.

For more details about each cleaning procedure, refer to SI document #5501008 – K71 Transmission Control Module: Scan Tool Information.

 

Fig. 22

 

Perform the DTC solenoid cleaning procedure three times for each DTC set. Once the cleaning procedure has been completed three times, select the Configurations/Reset Functions in order to perform the Transmission Service Fast Learn procedure as needed.

Be sure to test drive the vehicle after performing the cleaning procedures to verify that the DTCs do not reset. If the DTCs reset, replace the Control Valve Solenoid (or Main Control Valve, MCV).

For additional information, refer to Bulletin #21-NA- 033.

 

– Thanks to Dave Rainey

 

Updated March 1,2021

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