P23D4Cylinder 1 Fuel Heater Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P23D4 is not about wiring at all: the cylinder 1 heater circuit is electrically intact, yet it fails to heat as it should. The heater unit measures what each heat circuit delivers, so a heater that draws too little current, warms too slowly or reaches a lower temperature than its neighbours stands out. Bosch notes that its Flexstart unit keeps track of the heat energy put out by each of four separate circuits and reports the measured temperature to the engine module. Aging elements, deposits on a heated injector or a high-resistance contact are plausible reasons. No manufacturer documents P23D4 or its limits publicly. CARB asks for functional monitoring of heated fuel preparation. Cold starts may be rough on one cylinder; P23D1 to P23D3 cover the electrical faults.
- What you may notice
- Cylinder 1 runs rough for a while after a cold start on ethanol
- Longer cranking in cold weather
- Engine warning lamp, depending on manufacturer
- Likely causes
- LikelyAged cylinder 1 heater with reduced heating power
- PossibleHigh-resistance connection in the cylinder 1 heater circuit
- RareDeposits reducing heat transfer at a heated injector
- RareLow battery voltage during the heating phase
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.