DTC codes / P09xx · Transmission / P0904
P0904 indicates that the transmission control module (TCM) has detected an implausible or missing signal from the gate select position circuit, which reports the physical position of the automatic transmission's shift gate. The TCM compares this signal with other range and speed inputs and sets the code when the gate position does not match expected values or the circuit voltage falls outside its valid range.
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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