Powertrain, generic (extended)

P24F6 Exhaust Aftertreatment Fuel Air Purge Valve Stuck Open

Check engine lightOn

EmissionsRelevant

Drive cycleRequired

Limp modePossible

Heavy Volvo and Mack trucks regenerate the particulate filter with an aftertreatment hydrocarbon injector (AHI, the 7th injector) that sprays diesel ahead of the oxidation catalyst; compressed air from the truck supply then blows the line to the nozzle clear. P24F6 means the fuel/air purge valve in the AHI module seems to stay open, so air keeps flowing when it should not. Solution K17696792 (US15 and later, 11, 13 and 16 L engines) lists checks when guided diagnostics finds nothing: 32 psi (221 kPa) at the doser air supply, a dry purge line, the right coalescing air-dryer cartridge and no aerated fuel. For the open case Volvo's AHI guide also replaces the nozzle and cleans the line. Regeneration can fail and soot builds up.

Likely causes

Oil or water in the purge air from an unsuitable or worn air-dryer cartridge

Debris holding the purge valve in the AHI module open

Damaged AHI nozzle or leaking fuel/air line toward the nozzle

Doser air supply pressure outside the 221 kPa specification

Symptoms

Particulate filter regeneration does not complete
Warning lamp and aftertreatment message on the dash
Rising soot load and more frequent regeneration requests

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

P24F7 P24F8 P20CF P20DC P20DE

References: static.nhtsa.gov, static.nhtsa.gov, law.cornell.edu.