P256C code meaning
Engine Idle Speed Selector Sensor/Switch Circuit Low
What P256C means
P256C says the idle speed selector input is pulled below its lowest valid level, typically by a signal wire shorted to ground or a switch with an internal short. Where the selector is a simple ground-switched input, the controller would read such a short as a permanent request, so a dedicated low code presupposes a coded or monitored circuit. No manufacturer documents P256C publicly. A raised idle that appears without driver input is not automatically this fault: Ram's 2025 6.7L Cummins bulletin S2509000007 lists automatic modes such as cab warm-up at 1000 rpm below 4.4 °C ambient or inverter support between 700 and 1500 rpm. P256D is the high-side code. Expect the raised idle to be unavailable or the code to return after every key cycle.
P256C at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyEasy, DIY possible
- Typical labor0.3 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P256C
- Raised idle unavailable
- Code returns after every key cycle
Common causes of P256C
- Most likelyIdle selector wire shorted to ground
- PossibleInternal short in the idle selector
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Idle speed selector switch
What each part of P256C means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 5 | Area: vehicle speed, idle control and auxiliary inputs. |
| 6C | The exact fault in that area. |
What to do next
- Note P256C and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P256C
What does P256C mean?
P256C means "Engine Idle Speed Selector Sensor/Switch Circuit Low". P256C says the idle speed selector input is pulled below its lowest valid level, typically by a signal wire shorted to ground or a switch with an internal short. It is a generic code, so it means the same on every make.
Is it safe to drive with P256C?
P256C does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P256C fail an emissions test?
P256C is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P256C to fix?
Difficulty: easy. A typical repair takes 0.3 to 1.5 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P256C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.