P2DDCFuel Injection Quantity C Lower Than Expected
- 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
- P2DDC is the shortfall code for a third injection path, C. Engines that need it split their injection into more parts than A and B, for example by injector group or by operating mode; the split is defined by the maker, and none documents P2DDC openly. How narrowly such a monitor is allowed to run shows in GM's 2025 diesel tables for path A: warm coolant above 70 °C, 1,100 to 1,800 rpm, 18 to 40 mm³ per stroke, steady fueling and at least 20 km/h, and only in normal and SCR warm-up combustion modes, not during filter regeneration. Its correction may add at most about 12 to 41 mm³; if path C lacks more than that, the code follows. Likely culprits are injectors of this group and weak supply pressure.
- What you may notice
- Check engine light on
- Reduced power at part load
- Hesitation when accelerating
- Likely causes
- LikelyInjectors of group C coked or partly blocked
- PossibleLow-pressure supply weak (lift pump, filter, air in fuel)
- RareHigh resistance in injector wiring of group C
- 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: €100 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.