OBD-II code · Powertrain (generic, extended)
P256A Engine Idle Speed Selector Sensor/Switch Circuit/Open
The idle-speed selector input is open. On commercial vehicles this switch lets the operator pick a fast-idle setpoint (for example to keep auxiliary loads supplied). With the input broken, the ECM cannot apply an operator-selected idle speed.
Is it safe to drive with P256A?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOpen wire or unplugged switch
- Less likelyPin pushed back out of connector body
- Less likelyCracked solder joint inside the module or sensor
Symptoms
- Check engine light on
- Idle speed too high, too low, or unstable
- Possible stalling at idle or after cold start
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Often, with basic tools
- Typical labour
- 0.3–1.5 h
- Emissions test
- Usually unaffected
- Parts involved
- Idle Speed Selector Switch, Wiring Harness
Related codes
- P2567Turbocharger Boost Control Position Sensor Circuit Low
- P2568Turbocharger Boost Control Position Sensor Circuit High
- P2569Direct Ozone Reduction Catalyst Temperature Sensor Circuit Low
- P256BEngine Idle Speed Selector Sensor/Switch Range/Performance
- P256CEngine Idle Speed Selector Sensor/Switch Circuit Low
- P256DEngine Idle Speed Selector Sensor/Switch Circuit High
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.