P0430: Catalyst System Efficiency Below Threshold (Bank 2)
The catalytic converter on the second side of a V engine is not cleaning exhaust well enough.
Severity: 2 of 4
Usually drivable for a short time with a steady light and normal running. Plan a diagnosis soon. A flashing light, sulfur smell with power loss, or a red hot converter means park it.
Estimate range covers the repairs listed below; see the cost breakdown. A flashing check engine light, a hot temperature gauge, or brakes that feel different mean stop driving and get help.
What P0430 means
P0430 is the same test as P0420 but for bank 2, the side of a V6 or V8 engine that does not contain cylinder number 1. The computer compares the oxygen sensor ahead of the converter with the one behind it. If the rear sensor signal starts swinging like the front one, the converter is judged to be storing too little oxygen.
Inline four cylinder engines do not have a bank 2, so you will only see this code on V engines and some flat or W designs.
If both P0420 and P0430 appear together, look for something that affects the whole engine, such as misfires, a fuel problem, or oil consumption.
Common causes (cheapest likely first)
- Exhaust leak near the bank 2 sensors. Cracked manifolds and loose flanges are common on V engines and can mimic a bad converter.
- Slow rear oxygen sensor on bank 2. An inexpensive part that should be tested before a converter.
- Misfire or rich running on bank 2. Unburned fuel overheats the catalyst. Look for misfire codes or fuel trim problems on that side.
- Oil or coolant contamination. Internal engine leaks coat the catalyst and reduce its efficiency.
- Worn bank 2 catalytic converter. Common at high mileage; confirm the other causes first.
Symptoms
- Steady check engine light
- Often no noticeable change in driving
- Sulfur smell
- Failed emissions test
- Rattle from the exhaust if the substrate is broken
DIY difficulty: Moderate
Same as P0420. Access to bank 2 sensors can be tight near the firewall on some vehicles, so allow extra time.
Tools: OBD-II scanner with live data, Oxygen sensor socket, Penetrating oil, Jack and jack stands
Estimated repair cost
This is an estimate, built from typical parts price ranges plus labor hours times an assumed shop rate of $110 to $190 per hour. Actual prices vary by vehicle, region, and shop. Diagnosis fees are often extra.
| Repair | Parts | Labor | Estimate (low / high) |
|---|---|---|---|
| Rear oxygen sensor, bank 2 | $30 to $120 | 0.3 to 1.2 h | $30 + 0.3 × $110 = $63 $120 + 1.2 × $190 = $348 |
| Exhaust leak repair | $15 to $150 | 0.5 to 2.0 h | $15 + 0.5 × $110 = $70 $150 + 2.0 × $190 = $530 |
| Bank 2 catalytic converter (aftermarket) | $250 to $1,400 | 1.0 to 3.0 h | $250 + 1.0 × $110 = $360 $1,400 + 3.0 × $190 = $1,970 |
Watch a repair video
P0420 How To Diagnose A Bad Catalytic Converter (EricTheCarGuy); same test applies to bank 2. Third-party video, loads from YouTube (privacy-enhanced mode) only when you press play. Procedures vary by vehicle. Search YouTube for “P0430 fix” videos.
P0430 by make
Brand specific notes: Nissan, Chevrolet. Other makes: the code works the same way; see all makes.
Repair manuals
Step-by-step service manuals with torque specs and wiring diagrams:
Haynes manuals Chilton manuals
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Related codes
Check for recalls
Before paying for a repair, enter your VIN in the NHTSA recall lookup. Emissions parts may also be covered by a federal emissions warranty; check your warranty booklet.
FAQ
What is the difference between P0420 and P0430?
Only the side of the engine. P0420 is bank 1, the side with cylinder 1. P0430 is bank 2.
Can I drive long distances with P0430?
With a steady light and a smooth running engine many people do, but you risk further damage if the cause is a misfire. Get it diagnosed before a long trip.
Why would only one converter fail?
Each bank can have its own problem, such as a leaking injector or an exhaust leak on that side, which wears its converter faster.