Powertrain
generic / SAE
P21C2
Reductant Heater Relay Control Circuit/Open
The control circuit for the relay that powers the DEF heaters is open — main DEF heating supply path interrupted.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number1 / C2
Possible causes
- Relay coil open high
- Pin pushed back out of connector body low
- Cracked solder joint inside the module or sensor low
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)
Inspection / repair
- Difficulty: medium
- DIY: possible
- Estimated cost: 50–400 €
- Estimated time: 0.5–2 h
- Component: reductant heater relay
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012