What Does P0430 Mean?
The catalytic converter on bank 2 is not converting exhaust pollutants efficiently enough to meet emissions standards. The PCM detected this by comparing the front and rear oxygen sensor signals — the rear sensor is switching too closely to the front, indicating the catalyst is no longer storing and releasing oxygen properly. The driver may notice a sulfur (rotten egg) smell and will fail emissions testing.
Common Causes
40%
Worn-out or degraded catalytic converter (age or mileage related)
25%
Contaminated catalytic converter from oil or coolant burning
15%
Faulty rear oxygen sensor (Bank 2 Sensor 2) providing incorrect feedback
12%
Exhaust leak before the rear oxygen sensor skewing readings
8%
Engine running rich or lean on bank 2 overwhelming the catalyst
Diagnostic Steps
1
Monitor both the front (B2S1) and rear (B2S2) oxygen sensor waveforms at steady 2500 RPM — the rear sensor should show a relatively flat, steady line near 0.6–0.8V. If it mirrors the front sensor switching, the catalyst is degraded.
2
Check long-term fuel trims for bank 2 — values beyond +/- 10% indicate a fueling issue that may be damaging the catalyst or causing a false P0430.
3
Inspect for exhaust leaks between the front oxygen sensor and the rear sensor — use a smoke machine or soapy water spray with the engine running.
4
Verify the rear oxygen sensor response with propane enrichment — introduce propane at the intake and the rear sensor should respond slowly (several seconds delay) if the catalyst is healthy.
5
Check for oil or coolant consumption that could contaminate the catalyst — blue smoke on startup (valve seals) or white smoke continuously (head gasket) point to catalyst poisoning sources.
Estimated Repair Cost
$500 - $2,500
Parts + labor, varies by vehicle and location
The catalytic converter on bank 2 is not converting exhaust pollutants efficiently enough to meet emissions standards. The PCM detected this by comparing the front and rear oxygen sensor signals — the rear sensor is switching too closely to the front, indicating the catalyst is no longer storing and...
The most common cause of P0430 (Catalyst System Efficiency Below Threshold (Bank 2)) is: Worn-out or degraded catalytic converter (age or mileage related)
Typical repair costs for P0430 range from $500 to $2,500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Safe to drive. The primary concern is elevated emissions. A severely degraded catalyst can eventually become restricted, reducing power and potentially overheating. Repair is required for emissions compliance.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0430 to identify the root cause.
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Quick Info
Category
Powertrain
System
Exhaust / Catalytic Converter
Difficulty
Type
Generic (SAE)
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