P23C9Fuel Heater Control Module Power Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P23C9 is stored when the power control line to the fuel heater control unit shows battery voltage although the engine module has it switched off, pointing to a short to a live wire. The real risk here is the reverse of the low case: the heater stage may be enabled without being asked, warming the fuel after it is no longer needed and loading the electrical system. No manufacturer documents P23C9 publicly. Bosch lists reverse voltage and internal overtemperature protection for its Flexstart heating unit, which limits damage, and the engine module normally only heats depending on ethanol content and outside temperature. CARB requires output circuits of heated fuel systems to be checked. P23C7 covers the open and P23C8 the low fault.
- What you may notice
- Fuel heating active when not needed, possible battery drain
- Heater unit or wiring gets unusually warm
- Engine warning lamp, depending on manufacturer
- Likely causes
- LikelyPower control wire shorted to a battery or ignition feed
- PossibleWelded relay contact keeping the circuit energized
- PossibleInternal leakage in the fuel heater control module
- RareEngine module output that does not switch off
- 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.