P20BE
Reductant Heater B Control Circuit Performance
Reductant heater B is electrically OK but does not warm the line in time — partial winding fault or excessive heat loss.
- 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 winding faultCommon
Parts involved
- Reductant Line Heater B
P20BE 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.