P256E records an idle speed selector signal that drops out or flickers for short moments, more often than real switch use would cause. Since the selector is usually operated with the engine idling for long periods, engine vibration, a worn rocker switch or a loose crimp can be enough; each interruption can cancel the raised idle and make the engine fall back and rise again. Ram's 2012 chassis cab guide describes an Idle Up set speed that is entered when the function is activated, so repeated on-off events are noticeable as speed changes. No manufacturer publishes P256E. CARB requires circuit faults on monitored inputs to be watched continuously. A steady break would set P256A instead. The driver mainly notices an unsteady raised idle.
Low severity. Can I keep driving?Yes, you can normally keep driving. If it stalls at intersections or traffic circles, avoid driving until it is repaired.
Symptoms
- Raised idle drops out and comes back
- Engine speed rises and falls at standstill
- Code stored only intermittently
Most likely causes
- Worn rocker or toggle switch
- Loose crimp or terminal in the selector circuit
- Harness moving with engine vibration at idle
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: easy
What each character of P256E means
- P: Powertrain: engine and transmission
- 2: Generic code: same on every make
- 5: Speed and idle
- 6E: Specific fault in that system
Frequently asked questions
Can I keep driving with code P256E?
Yes, you can normally keep driving. If it stalls at intersections or traffic circles, avoid driving until it is repaired.
What causes code P256E?
The most common causes are: worn rocker or toggle switch; loose crimp or terminal in the selector circuit; harness moving with engine vibration at idle.
Related codes
- P256AEngine Idle Speed Selector Sensor/Switch Circuit/Open
- P256BEngine Idle Speed Selector Sensor/Switch Range/Performance
- P256CEngine Idle Speed Selector Sensor/Switch Circuit Low
- P256DEngine Idle Speed Selector Sensor/Switch Circuit High
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.