Powertrain, generic (extended)

P20D8 Exhaust Aftertreatment Fuel Supply Control Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

The supply valve ahead of the exhaust doser is electrically sound, but the pressure it produces in the feed line does not follow its commands. A typical layout, described in a patent assigned to International Engine, measures that line pressure and uses it both to meter the dose and to diagnose the regulating valve. Hino's J08E manual lists P20D8 among the codes to resolve before chasing a regeneration fault; its trucks use a fuel cut valve ahead of the dosing injector. CARB treats a supply that runs out of control authority as a feedback fault. Circuit faults are P20D7, P20D9 and P20DA; a valve fixed open or shut is P20DB or P20DC.

Likely causes

Sluggish or contaminated supply valve
Low feed pressure from a clogged fuel filter or weak low-pressure pump
Line pressure sensor reading off

Symptoms

  • Check engine light on
  • Regenerations take longer or fail

Repair estimate

DifficultyHardWorkshop job
Parts and labour€150–1,500
Time1–3 h

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

Parts involved

aftertreatment fuel supply solenoidaftertreatment fuel pump

Related codes

P20D7P20DBP20DCP20DEP0005

References: static.nhtsa.gov, patents.google.com, law.cornell.edu.