DTC codes / P25xx · Vehicle speed, idle control and auxiliary inputs / P251F
P251F indicates that the Powertrain Control Module (PCM) has detected an abnormally high voltage on the Power Take-Off (PTO) engine shutdown circuit, which is used to remotely kill engine power for auxiliary equipment operation. The PCM expects a specific voltage range on this circuit, and a reading above the threshold triggers the code, often disabling the PTO function or preventing engine start.
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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