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DTC codes / P25xx · Vehicle speed, idle control and auxiliary inputs / P255D

P255DPTO Speed Selector Sensor/Switch 2 Circuit High

P255D indicates that the powertrain control module (PCM) has detected an abnormally high voltage on the signal circuit for the PTO (power take-off) speed selector sensor or switch number 2. This sensor or switch is used on vehicles with a power take-off system to select and monitor the speed of the PTO output, and a high voltage reading typically means the circuit is open, shorted to voltage, or the sensor/switch has failed.

SystemPowertrain
Code typeGeneric (all makes)
SeverityLow
Fix difficultyIntermediate
AreaVehicle speed, idle control and auxiliary inputs

Symptoms you may notice

  • The check engine light or service engine soon light is illuminated.
  • The PTO system may fail to engage or may operate only in certain speed ranges.
  • The PTO speed selector may not respond when the operator changes settings.
  • The vehicle may enter a limp-home mode or limit engine speed to protect the PTO system.
  • Often no symptoms besides the warning light, especially if the PTO is not in use.

Common causes, most likely first

  1. Faulty PTO speed selector sensor or switch number 2.
  2. Open or damaged wire in the signal circuit between the sensor/switch and the PCM.
  3. Short to voltage on the signal circuit, often due to chafed insulation or moisture intrusion.
  4. Corroded or loose electrical connector at the sensor/switch or PCM.
  5. Failed PCM driver or internal circuit for the PTO speed selector input (rare).

How to diagnose and fix it

  1. Use a scan tool to verify P255D is current and check for any related codes in the PTO system.
  2. Inspect the sensor/switch connector and wiring for damage, corrosion, or loose pins, and repair as needed.
  3. Disconnect the sensor/switch and measure resistance across its terminals; compare to the manufacturer's specification.
  4. Check the signal circuit for a short to voltage by measuring voltage with the sensor disconnected and the key on; repair any short.
  5. Check the signal circuit for an open by measuring continuity from the sensor connector to the PCM; repair any open.
  6. If the wiring and sensor/switch test good, substitute a known-good sensor/switch and clear the code to see if it returns.
  7. If the code persists after all checks, diagnose the PCM and replace only if confirmed faulty.

When P255D is not the sensor's fault

  • A common misdiagnosis is replacing the PTO speed selector sensor when the real problem is a chafed wire shorting to voltage near a heat source or moving component.
  • The code can set intermittently due to water intrusion in the connector, so a visual inspection after a rainstorm or car wash is worthwhile.
  • On some vehicles, P255D may be stored alongside communication codes if the PCM is losing signal from the PTO module, so check for related codes before condemning the sensor.
  • A high voltage reading does not always mean the sensor is bad; a poor ground at the sensor or PCM can skew the signal voltage high.
  • If the PTO system is not used, the code may have no effect on drivability, but ignoring it can mask a wiring fault that later affects other circuits.

Can I keep driving with P255D?

The vehicle is generally safe to drive if the PTO system is not in use, but avoid using the PTO until the fault is repaired because the speed selector may not function correctly. If the vehicle enters a limp mode or the PTO is essential for work, have it diagnosed promptly.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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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