P202F
Reductant/Regeneration Supply Control Circuit Range/Performance
The control line that gates the DEF supply pump or the regeneration heating circuit does not respond as commanded — duty cycle, current draw, or response time off-spec.
- 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.
- Supply relay aged or pitted contactsCommon
- Supply pump motor brushes wornPossible
- Sensor element aged beyond calibration windowLess likely
Parts involved
- Reductant Supply Pump
- Reductant Supply Relay
P202F 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.