2012 Infiniti P0420: What It Means & Is It Safe to Drive?
P0420 on the 2012 Infiniti: 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 2012 Infiniti
- 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 2012 Infiniti, repairs for P0420 typically fall between $400 and $2400, depending on the root cause and labor rates in your area.
Known issues on Infiniti
VQ35DE and VQ37VHR engines are among the most common P0420 triggers in Infiniti vehicles. P0420 and P0430 often appear together on V6 models—address both banks when diagnosing.
Most commonly affected models
G35 2003–2006G37 2008–2013Q50 2014–2019