OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P251B

PTO Enable Switch Circuit Low

The PTO enable switch input reads stuck low — typically a short to ground or a permanently closed switch. The ECM either sees PTO enabled when the operator has not requested it, or cannot release the PTO mode after work.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / 1B

Possible causes

  • Switch wire shorted to ground high
  • Switch stuck closed medium
  • Connector pins corroded - high contact resistance low

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 60–350 €
  • Estimated time: 0.3–1.5 h
  • Component: pto enable switch
  • Component: wiring harness
  • MIL / check engine light

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication