DTC codes / P28xx · Transmission / P2821
P2821 indicates that the transmission control module (TCM) has detected a fault where pressure control solenoid J is stuck in the energized or on state, meaning it is commanding hydraulic pressure when it should not be. The TCM monitors the solenoid's electrical circuit and hydraulic response, and when the signal or pressure does not match the commanded state, it sets this code and typically illuminates the malfunction indicator lamp (MIL).
Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.
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