P0431 on Mitsubishi
Warm Up Catalyst Efficiency Below Threshold (Bank 2)
P0431 on Mitsubishi vehicles indicates warm up catalyst efficiency below threshold (bank 2). Au7o has documented this code across 1 Mitsubishi model — most commonly on Endeavor. On vehicles with a primary/warm-up catalyst, the PCM determines the Bank 2 warm-up catalyst (WU-TWC) is below its efficiency threshold, based on the upstream/downstream O2 sensor comparison for that bank. Typical repair costs on Mitsubishi range from $600 to $2,000, depending on the specific model and root cause.
Common Causes of P0431
- •Worn/failed Bank 2 warm-up catalytic converter
- •Aged or contaminated O2 sensor on Bank 2
- •Exhaust leak near the warm-up catalyst
- •Misfire or improper air/fuel on Bank 2
- •Oil/coolant contamination
P0431 on Mitsubishi by Model
Mitsubishi Endeavor(1 issue)
- Manifold Pre-Catalyst Efficiency Failure Setting P0421 or P04312004-2011
The 6G75 Endeavor runs three catalysts: a pre-cat integrated at each exhaust manifold plus an unmonitored underfloor unit. Only the two manifold pre-cats are monitored, so a check-engine light for catalyst efficiency always points at a manifold cat, never at the big underfloor converter that most quick-lube shops quote. Owners and techs confirm the mapping on this engine: the right (windshield-side) bank sets P0421 and the left (radiator-side) bank sets P0431. The pre-cats sit right at the head and cook, and they are commonly killed early by an upstream problem - a misfire or leaking injector dumping raw fuel into the converter.
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View P0431 across all makes →Frequently Asked Questions
What does P0431 mean on Mitsubishi?▼
P0431 stands for "Warm Up Catalyst Efficiency Below Threshold (Bank 2)." On vehicles with a primary/warm-up catalyst, the PCM determines the Bank 2 warm-up catalyst (WU-TWC) is below its efficiency threshold, based on the upstream/downstream O2 sensor comparison for that bank. On Mitsubishi specifically, this code is documented across 1 model.
What causes P0431 on Mitsubishi vehicles?▼
Common causes on Mitsubishi: Worn/failed Bank 2 warm-up catalytic converter, Aged or contaminated O2 sensor on Bank 2, Exhaust leak near the warm-up catalyst, Misfire or improper air/fuel on Bank 2, Oil/coolant contamination. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0431 on a Mitsubishi?▼
Repair costs on Mitsubishi range from $600 to $2,000, depending on the specific model and root cause.
Which Mitsubishi models have P0431 documented?▼
Au7o has documented P0431 on 1 Mitsubishi model: Endeavor.