P23DFCylinder 4 Fuel Heater Control Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P23DF marks the cylinder 4 heater control circuit as low, which in practice is a short to ground between the control unit and the heater. The channel then stays off until the next start. On four-cylinder engines cylinder 4 is the outermost rail outlet, where the harness often passes brackets and hot components; chafed insulation there, a heating element shorted to its housing and moisture in the plug are the usual suspects, an internally shorted output in the control unit less so. No manufacturer documents P23DF publicly; the CARB rule expects such outputs to be checked for circuit faults. In daily use the fault shows as a rough cold start on one cylinder, sometimes together with a tripped fuse. Its high counterpart is P23DE, the open circuit P23DD.
- What you may notice
- Rough cold start on one cylinder
- Tripped fuel heater fuse
- Engine warning lamp, depending on manufacturer
- Likely causes
- LikelyChafed insulation on the cylinder 4 heater lead at the rail end
- PossibleHeating element at cylinder 4 shorted to its housing
- PossibleMoisture in the cylinder 4 heater plug
- RareShorted channel 4 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.