Catalyst monitoringDiagnose promptlyReviewed July 15, 2026
P0430Catalyst system efficiency below threshold — Bank 2
The Bank 2 catalyst monitor calculated efficiency below its calibrated threshold during a qualifying test.
Conditions that can produce P0430
These are diagnostic branches, not a ranked parts list. Prevalence and testing order depend on the exact vehicle and failure scene.
- Bank 2 catalyst deterioration or contamination
- Bank-specific misfire, fueling, or oil/coolant entry
- Exhaust leak near the monitored path
- Incorrect or biased sensor
- Calibration or non-original exhaust component issue
What to inspect next
- Confirm Bank 2 identity and exhaust layout
- Compare equivalent Bank 1 and Bank 2 signals and monitor results
- Resolve upstream combustion or mixture faults
- Verify part application before catalyst replacement
Evidence that strengthens the answer
Bank-to-bank response under comparable conditionsExact Mode $06 resultsExhaust integrity and temperature evidenceFuel-control and misfire history
Verify the repair
Preserve the pre-repair record, document exactly what changed, then repeat the relevant operating condition safely. Confirm no current or pending fault returns, review permanent-code and readiness state where applicable, and state which tests or modules remained unavailable.
This page explains a commonly standardized code at a general level. Confirm the exact definition, module, status, test conditions, thresholds, wiring, and service process for the vehicle application using current official information.