Powertrain, generic (extended)

P24F7 Exhaust Aftertreatment Fuel Air Purge Valve Stuck Closed

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P24F7 is the reverse case of P24F6: the purge valve of the aftertreatment fuel/air system will not open when commanded, so no compressed air reaches the dosing line and the 7th injector after a dosing phase. In Volvo and Mack trucks this valve sits in the AHI dosing block, mounted on the fuel filter housing from model year 2017 and on the engine block side before. Volvo's AHI troubleshooting guide points to the air supply, the module and the fuel/air lines up to the nozzle; contamination carried in with the air or fuel causes most module failures. The joint solution for both purge codes was reissued as KC-401 for trucks from model year 2016 and starts with the 221 kPa air pressure check. Without purging, fuel can coke in the line.

Likely causes

Purge valve jammed by oil, water or particles from the air system
Air supply to the AHI module restricted or below specification
Coked or kinked line between AHI module and nozzle
Internal fault of the AHI dosing module

Symptoms

  • Active regeneration aborted or not started
  • Warning lamp with aftertreatment message
  • Possible engine derate as soot load climbs

Repair estimate

DifficultyHardWorkshop job
Parts and labour€200–1,500
Time1–4 h

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

Parts involved

aftertreatment purge valvedosing line

Related codes

P24F6P24F8P20D0P20DCP20DE

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.