Powertrain, generic (extended)

P20CC Exhaust Aftertreatment Fuel Injector A Control Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Unlike the circuit codes, this one judges what the hydrocarbon doser actually does. On the 6.6 L Duramax LML/LGH, GM table 15OBDG09 sets it when the outlet of the oxidation catalyst runs more than 300 °C hotter than its inlet for 180 s although no regeneration is under way and more than 900 s have passed since the last one; that heat can only come from fuel the doser should not be delivering. It is a Type A fault, so the MIL comes on after one trip. To keep the nozzle free, the same GM software pulses it briefly at 100 Hz at set soot levels. CARB requires makers to flag any injection fault that stops the filter from regenerating. Stuck positions have separate codes (P20CF, P20D0).

Likely causes

Doser leaking or dribbling fuel into the exhaust while closed
Coked nozzle tip with distorted spray
Exhaust temperature sensor before or after the catalyst reading wrong

Symptoms

  • Check engine light on
  • Unexpectedly high exhaust temperatures, possibly white smoke or fuel smell
  • Higher fuel consumption

Repair estimate

DifficultyHardWorkshop job
Parts and labour€300–1,500
Time1–3 h

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

Parts involved

aftertreatment fuel injector

Related codes

P20CBP20CFP20D0P20D2P2698P20E2

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