Powertrain, generic (extended)

P2DD7 Cold Start Fuel Injection Quantity B Lower Than Expected

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modeNo

P2DD7 limits the shortfall of P2DD5 to the cold-start phase. Many engines inject differently just after a cold start, with extra or shifted injections that heat the catalyst or SCR system. CARB section 1968.2 (f)(12.1.2) requires diesels to keep faults found while this strategy runs apart from the same faults in normal operation, and (f)(12.2.3) adds a check that the commanded injection quantity actually responds, phased in over 2026 to 2028. GM's 2025 diesels show the pattern with separate cold-start codes for rail pressure (P2C1F) and injection timing (P05EC), but not for quantity. No maker documents P2DD7. Fuel thickened by cold, a clogged filter or slow pressure build-up fit here; the engine may run roughly until warm.

Likely causes

Fuel filter restricted, fuel waxing in cold weather

Rail pressure builds too slowly after start

Injectors of group B sluggish or partly blocked

Coolant or fuel temperature signal implausible

Symptoms

Check engine light on after a cold start
Hard cold start, rough running while cold
Longer warm-up

Repair estimate

DifficultyHardWorkshop job

Parts and labour€80–3,000

Time0.5–5 h

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

Parts involved

fuel injector group bfuel railecm

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