Powertrain, generic (extended)

P20A5 Reductant Purge Control Valve A Stuck Closed

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Stuck closed is the failure in which the purge valve does not switch to the reverse position when the system wants to empty the line. For the CNRB engine of the 2014 Touareg, Volkswagen bases P20A5 on the pressure difference between the start of the pressure reduction and the current value. Ford reports the code on 6.7 L diesel Super Duty trucks of model years 2023 to 2025, F-650/F-750 included: TSB 24-2055, 24-2379 and 25-2032 trace an illuminated MIL with P20A5 to a software issue of the glow dosing module, shown in the scan tool as secondary OBD control module, and cure it by reprogramming; driving is not affected. On other vehicles a jammed valve or a blocked return line is the real cause. P20A4 is the reverse case. A line left full can freeze and crack in winter.

Likely causes

Control module software (Ford 6.7 L, reprogram the glow dosing module)
Valve jammed in the delivery position by crystallized DEF
Return line to the tank kinked or blocked
DEF pressure sensor frozen at one value

Symptoms

  • MIL on, often found after a shutdown cycle
  • No change in driveability (Ford software case)
  • Frost damage to line or injector if a real valve fault persists

Repair estimate

DifficultyHardWorkshop job
Parts and labour€0–1,600
Time0.3–3 h

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

Parts involved

reductant purge valve

Related codes

P20A4P20A1P20A0P24E0

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