P23CFFuel Heater Control Module Feedback Signal Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P23CF is logged when the feedback line from the fuel heater control unit stays near ground, below its valid signal range. Mostly the wire is chafed against ground or the feedback output inside the unit is shorted. Depending on how the signal is coded, a permanently low level can also look like a heater that never reports a result, which is why the engine module treats it as a circuit fault rather than as real data. No manufacturer documents P23CF publicly; the background is the temperature and diagnostic feedback that Bosch describes for its Flexstart heater unit. CARB requires the inputs of monitored emission components to be checked for out-of-range values. Cold-start heating may be suppressed. The high-side counterpart is P23D0, a missing signal P23CD.
- What you may notice
- Fuel heating not used for cold starts
- Long cranking with ethanol in cold weather
- Engine warning lamp, depending on manufacturer
- Likely causes
- LikelyFeedback wire shorted to ground
- PossibleMoisture in a connector of the feedback circuit
- PossibleShorted feedback output in the fuel heater control module
- RareFaulty input stage in the engine 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.