P23D1Cylinder 1 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
- Instead of one heater for the whole rail, some flex-fuel systems give every cylinder its own heating path, either a heated injector or an element at each rail outlet. P23D1 is the open or general circuit fault on the path for cylinder 1, so that cylinder gets unheated ethanol during a cold start. Bosch's Flexstart heating control unit supervises four separate heat circuits of about 260 W each and recognises interruptions, which matches this per-cylinder layout. No manufacturer documents P23D1 publicly. CARB lists heated fuel preparation as an output component to be monitored. Typically cylinder 1 misfires or contributes nothing in the first seconds after a cold start. Cylinders 2 to 4 follow from P23D5 onwards; a rail-wide heater uses P23CA.
- What you may notice
- Cylinder 1 misfire right after a cold start on ethanol
- Rough idle until the engine warms up
- Engine warning lamp, depending on manufacturer
- Likely causes
- LikelyBurnt-out heater at cylinder 1 (heated injector or rail element)
- PossibleBroken wire or unplugged heater connector at cylinder 1
- PossibleCorroded terminals in the cylinder 1 heater connector
- RareFailed channel 1 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: €60 – €500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.