Technical Service Bulletin
Some customers may experience momentary sharp deceleration during 1-2 upshift or momentary neutral during 2-4 upshift, followed by the transmission getting stuck in 2nd gear when the vehicle is cold (fluid below 32°F). The Malfunction Indicator Lamp (MIL) may also be illuminated, and DTC P2820 may be set.
The condition is caused by an undersized orifice in the spacer plate between the valve body and the transmission case, which can cause the clutch select to move slowly and release the selectable one-way clutch, resulting in a momentary transmission tie-up during the 1-2 upshift.
Correction
Inspect the valve body spacer plate orifice for proper size and replace as necessary. If the 0.5 mm orifice is validated, replace the separator plate. If the 2.0 mm orifice is validated, refer to SI for further diagnostics.
Manual:
Download: 2018 Buick Enclave, LaCrosse, GMC Terrain Service Bulletin No. 18-NA-054
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