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P255APTO Speed Selector Sensor/Switch 2 Circuit/Open

The PCM has detected an open or general fault in the PTO speed selector sensor/switch 2 circuit.

Definition

Vehicles with multi-input PTO speed control use a second selector input — often a preset-speed switch or redundant signal — so the PCM can validate the operator's requested PTO engine speed. P255A sets when selector circuit 2 is open or its signal is outside any valid electrical range, most often from disconnected upfitter wiring or a failed switch. PTO speed-control functions may be disabled or limited to a default speed, possibly with a MIL; normal driving is unaffected.

Common causes

  • Unconnected or incorrectly wired upfitter circuit for the second selector input
  • Failed PTO speed selector switch
  • Open in the signal or ground wiring to the selector
  • Corroded or backed-out terminal at the selector or upfitter connector
  • PCM PTO configuration enabling an input that is not physically installed

Common misdiagnoses

  • Replacing the PCM
  • Replacing the PTO unit
  • Replacing selector switch 1 when the fault is on the second input circuit

Troubleshooting steps

  1. 1.Confirm the input is supposed to exist

    Check the PCM's PTO configuration against the actual installation — if no second selector is fitted, correcting the configuration (not wiring) clears the fault.

  2. 2.Locate circuit 2 in the body-builder guide

    Identify the correct upfitter connector pin for selector input 2 for this model year so you are testing the right wire.

  3. 3.Test the switch and circuit

    Verify the switch changes continuity/resistance at each position and that the signal wire has continuity (under 1 ohm) from the switch to the upfitter/PCM connector.

  4. 4.Check supply and ground at the selector

    With key on, confirm the expected reference voltage and a good ground at the selector connector per the wiring diagram.

  5. 5.Repair, reconfigure, and verify

    After the wiring repair or configuration fix, exercise every selector position on live data and confirm the PCM registers each state without the code returning.

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