Powertrain, generic (extended)

P2DDC Fuel Injection Quantity C Lower Than Expected

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Injectors of group C coked or partly blocked
Low-pressure supply weak (lift pump, filter, air in fuel)
High resistance in injector wiring of group C

Symptoms

  • Check engine light on
  • Reduced power at part load
  • Hesitation when accelerating

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–3,000
Time0.5–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

fuel injector group cfuel railecm

Related codes

P2DDDP2DE0P2DD5P2DDEP026C

References: law.cornell.edu, gsi.ext.gm.com.