2019 Mini P0420: What It Means & Is It Safe to Drive?
P0420 on the 2019 Mini: Catalyst System Efficiency Below Threshold (Bank 1). Here's what it means, what usually causes it, what repairs typically cost, and whether it's safe to keep driving.
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What this code means
The downstream oxygen sensor detects that the catalytic converter is not storing or converting exhaust properly. This is one of the most common check engine codes.
Common causes on the 2019 Mini
- Failed or aging catalytic converter
- Faulty downstream oxygen sensor
- Exhaust leak before or after the catalyst
- Engine misfire or rich/lean condition damaging the catalyst
Symptoms
- Check Engine Light on
- Often no drivability issues
- Possible failed emissions test
- Rotten egg smell in some cases
Typical fixes
- Replace catalytic converter
- Replace oxygen sensor(s)
- Repair exhaust leaks
- Fix underlying fuel/ignition issues first
Repair cost range
For a 2019 Mini, repairs for P0420 typically fall between $400 and $2400, depending on the root cause and labor rates in your area.
Known issues on Mini
MINI's W11 and N14 engines trigger P0420 from carbon buildup and rich-running conditions. Fix any running issues before catalyst replacement, or the new unit will fail quickly.
Most commonly affected models
Cooper 2002–2008Countryman 2011–2016