P23DECylinder 4 Fuel Heater Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P23DE means the cylinder 4 heater control circuit is at a high level where the module expects otherwise. Either the line has contact with a voltage source, or the driving stage no longer switches off, so heater 4 may keep running. The risk lies less in starting than in overheating: Bosch states that its heated rail works with fuel temperatures from 70 up to 125 °C depending on system pressure, and that the heating element can tell when it is running in air or vapour. If cylinder 4 keeps heating once the engine is warm, vapour bubbles form at that outlet and hot restarts can suffer. No manufacturer documents P23DE publicly; CARB requires circuit monitoring. Low fault: P23DF, open: P23DD, performance: P23E0.
- What you may notice
- Hard restart when the engine is hot
- Uneven idle after hot soak
- Engine warning lamp, depending on manufacturer
- Likely causes
- LikelyChannel 4 driver no longer switching off
- PossibleCylinder 4 heater line touching a voltage source
- RareConnectors swapped or mismated after repair
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.