P23D9Cylinder 3 Fuel Heater Control Circuit/Open
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P23D9 is the open-circuit or general circuit fault of the heating path for cylinder 3. The fuel heater control unit drives each heater through a channel of its own; when channel 3 is switched on but no load current appears, the connection to the heater is considered broken. Bosch lists interruption among the faults its Flexstart unit diagnoses on all four heat circuits, and its heated rail can be configured for three- or four-cylinder engines, so on a triple cylinder 3 is the last heated outlet. No carmaker documents P23D9 publicly; CARB names heated fuel preparation as a monitored output. Below about 13 °C ethanol ignites poorly, so it is the unheated cylinder 3 that stumbles after a cold start. High and low faults on this path: P23DA and P23DB.
- What you may notice
- Stumble on cylinder 3 after a cold ethanol start
- Harder starting below about 13 °C
- Engine warning lamp, depending on manufacturer
- Likely causes
- LikelyOpen heating element at cylinder 3
- PossibleTerminal pushed out of the cylinder 3 heater connector
- RareWire broken where the harness flexes near the rail
- RareFailed channel 3 output in the heater unit
- 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.