P256BEngine Idle Speed Selector Sensor/Switch Range/Performance
- Generic OBD-II code · Powertrain
- How the car detects it
- P256B means the idle speed selector delivers a value that is electrically valid but makes no sense in context. The controller may, for instance, see a raised-idle request with the truck in motion, a position that does not exist, or a request that conflicts with an active PTO mode; Ram's 2012 chassis cab guide states that remote PTO outranks the Idle Up function, so the two inputs have a defined order the software can check. CARB defines a rationality diagnostic as comparing an input within its normal range with all other available information. No manufacturer publishes P256B. Likely causes are a sticking or misadjusted switch, aftermarket idle controls wired into the same circuit, or a configuration change. The idle request is usually ignored.
- What you may notice
- Raised idle request ignored
- Idle selection works only sometimes
- Likely causes
- LikelySticking or misadjusted idle selector
- PossibleAftermarket idle control wired into the same circuit
- RareIdle or PTO configuration changed without matching hardware
- Repair
- Medium · Often possible to do yourself.Typical cost: €20 – €300
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.