P23DBCylinder 3 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
- With P23DB the cylinder 3 heater control circuit is too low, meaning the line or the heater itself has found a path to ground. Because a single heat circuit is sized for several hundred watts, such a short trips the current limit at once; Bosch describes short detection per circuit and an integrated current relay in its Flexstart unit, which then cuts only the affected channel. Cylinder 3 starts on cold fuel while the remaining heaters keep working, so the engine shows roughness on one cylinder rather than a general cold-start problem. Water entering the connector, a damaged harness clip near the rail or an internally shorted heated injector are plausible causes. No manufacturer documents P23DB publicly; CARB requires circuit monitoring. Related: P23DA, P23D9, P23DC.
- What you may notice
- One-cylinder roughness when starting cold
- Other cylinders start normally
- Engine warning lamp, depending on manufacturer
- Likely causes
- LikelyWater in the cylinder 3 heater connector
- PossibleHarness chafed through at a damaged clip near the rail
- RareHeated injector at cylinder 3 shorted internally
- 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.