OBD-II code · Powertrain (generic)
P0431 Warm Up Catalyst Efficiency Below Threshold (Bank 2)
The pre-cat (warm-up) catalyst on bank 2 has lost too much oxygen storage capacity. Its primary purpose — quickly reaching light-off after a cold start — is no longer met within the OBD limits.
Is it safe to drive with P0431?
Usually safe for short trips, but don’t ignore it: the underlying fault can get more expensive over time.
Common causes
- Most likelyPre-catalyst aged or damaged
- PossibleOxygen sensor drift
Symptoms
- Check engine light on
- Failed emissions inspection
- Possibly slightly increased fuel consumption
- Sulfur (rotten egg) smell from exhaust under load
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–4 h
- Emissions test
- Likely to fail
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Warm Up Catalyst, Oxygen Sensor Upstream, Oxygen Sensor Downstream
Related codes
- P0421Warm Up Catalyst Efficiency Below Threshold (Bank 1)
- P0430Catalyst System Efficiency Below Threshold (Bank 2)
- P042EEGR A Control Stuck Open
- P042FEGR A Control Stuck Closed
- P0432Main Catalyst Efficiency Below Threshold (Bank 2)
- P0433Heated Catalyst Efficiency Below Threshold (Bank 2)
- P0434Heated Catalyst Temperature Below Threshold (Bank 2)
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.