DTC codes / P08xx · Transmission / P0839
P0839 indicates that the powertrain control module (PCM) has detected a high-voltage condition on the four-wheel drive (4WD) switch circuit, which is used to determine whether the vehicle is in two-wheel drive or four-wheel drive. The PCM expects a specific voltage range on this circuit, and a reading above the normal threshold triggers the code.
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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