P23CDFuel Heater Control Module Feedback Signal/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Besides being commanded, a fuel heater control unit reports back to the engine module, so the engine knows whether heating actually took place. P23CD indicates that this feedback line carries no usable signal or is open. Bosch describes exactly such a return path for its Flexstart unit: the delivered temperature and diagnostic status are measured and handed on to the engine module, which uses them to dose the heating energy. No manufacturer documents P23CD publicly. Without feedback the engine module cannot confirm heater operation, may stop using fuel heating and cannot evaluate the individual heater circuits. CARB requires monitoring of heated fuel preparation. Implausible feedback is P23CE; shorts of the line are P23CF and P23D0.
- What you may notice
- Cold-start fuel heating disabled or unconfirmed
- Harder starts on ethanol in cold weather
- Engine warning lamp, depending on manufacturer
- Likely causes
- LikelyBroken feedback wire between heater unit and engine module
- PossibleLoose or corroded pin for the feedback signal
- PossibleHeater unit without supply or ground, so it sends nothing
- RareFailed feedback output in the fuel heater control module
- 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: €50 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.