Powertrain
generic / SAE
P21CB
Reductant Control Module Supply Voltage Low
SCR control module supply voltage measured at the module pin is below the lower threshold.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number1 / CB
Possible causes
- Voltage drop in supply harness high
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: shop recommended
- Estimated cost: 80–800 €
- Estimated time: 0.5–3 h
- Component: scr control module
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012