DTC codes / P08xx · Transmission / P0820
P0820 indicates that the transmission control module (TCM) has detected an abnormal signal from the gear lever X-Y position sensor, which is typically a pair of potentiometers that report the lever's fore-aft and side-to-side position. The TCM compares these voltages against expected ranges and sets the code when the signal is out of range, erratic, or inconsistent between the two channels.
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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