Powertrain
generic / SAE
P204F
Reductant System Performance
The SCR (selective catalytic reduction) system using AdBlue/DEF is not delivering the expected NOx conversion. Causes range from poor reductant quality, dosing module faults, heater failure on the AdBlue tank in cold weather, or a degraded SCR catalyst.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number– / 4F
Possible causes
- Poor reductant quality or contamination high
- Dosing module clogged with urea crystals medium
- SCR catalyst aged or contaminated 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)
Inspection / repair
- Difficulty: hard
- DIY: shop recommended
- Estimated cost: 200–3000 €
- Estimated time: 1–6 h
- Component: scr catalyst
- Component: adblue dosing module
- Component: adblue tank heater
- Component: nox sensor
- MIL / check engine light
- emissions-relevant
- drive cycle required
- limp mode possible
Sources
References
sae:J2012