DTC codes / P09xx · Transmission / P0978
P0978 indicates that the powertrain control module (PCM) has detected an abnormal electrical condition in the control circuit for shift solenoid 'C', which is responsible for managing hydraulic pressure to a specific gear clutch pack. The PCM monitors the solenoid's commanded state versus actual circuit feedback and sets this code when the voltage or current falls outside the expected range for the commanded state.
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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