P20A1
Reductant Purge Control Valve A Performance
Reductant purge control valve A is electrically OK but does not vent the line within the expected time — partial blockage or weakened solenoid.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Common causes
Ordered by how often each turns out to be the cause.
- Partial blockage from crystallisationCommon
Parts involved
- Reductant Purge Valve
P20A1 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.