Conditions for Setting the DTC
WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.
P2817
During the 3-4 upshift the transmission did not obtain 4th gear, due to the transmission control solenoid valve 8, stuck in the Off position.
P2818
The torque converter clutch (TCC) slip speed obtains a low RPM value when the TCC is commanded on in park position, due to the transmission control solenoid valve 8, stuck in the On position.