P20A5Reductant Purge Control Valve A Stuck Closed
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- Needs a drive cycle to confirm a fix
- How the car detects it
- 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.
- What you may notice
- 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
- Likely causes
- LikelyControl module software (Ford 6.7 L, reprogram the glow dosing module)
- PossibleValve jammed in the delivery position by crystallized DEF
- PossibleReturn line to the tank kinked or blocked
- RareDEF pressure sensor frozen at one value
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €0 – €1,600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.