P0430 Catalytic Converter Efficiency Low (Bank 2)
Drive normally - check soon
The catalytic converter on bank 2 no longer cleans the exhaust well enough. Check exhaust leaks, the rear sensor and engine faults before you replace it. Safe to drive for now.
- Safe to drive?
- Yes, for now
- Typical cost at a shop
- $125-$2,480 RepairPal national averages, parts and labor
- Emissions test
- Yes, in most areas with OBD emissions testing, a lit check engine light fails the test.
- Carmaker bulletins
- 4 notes with links
What it means
This is P0420 on the other bank. The rear oxygen sensor behind bank 2's converter is seeing swings the converter should smooth out. It applies to engines with two exhaust banks: V6, V8 and some flat engines.
The technical version
The catalyst monitor compares bank 2's rear and front sensors, or measures oxygen storage, when the engine is warm and cruising. Comparing both banks is the fast diagnosis: one bank clean and one failing localizes the fault; both failing points to a shared cause upstream.
Official name: Catalyst System Efficiency Below Threshold (Bank 2).
Symptoms
- Often only the light.
- A failed emissions test.
- Sometimes a sulfur smell or a rattle underneath.
Causes, most likely first
| Cause | How likely | How to tell |
|---|---|---|
| A worn bank 2 catalytic converter | most common | No other codes, bank 2 rear sensor swings like the front. |
| Misfires, rich running or oil burning on bank 2 | common | Misfire counts on bank 2 cylinders, fuel trim far from 0%. |
| An exhaust leak around the bank 2 sensors | common | Ticking or soot marks. |
| A slow bank 2 rear oxygen sensor | less common | It does not reach both high and low ends. |
| With P0420 also set: a shared cause such as oil burning | less common | Both banks fail together. |
How likely is our ranking from repair data and common practice, not a published rate.
What the live data shows
Bank 2 sensor 2 following bank 2 sensor 1 is the sign, as with P0420 on the other side. Compare the banks: one calm rear sensor and one swinging rear sensor points to that bank's converter. Bank 2 fuel trims help rule mixture problems in or out. Our P0420 page shows what a failing rear sensor looks like on a real car.
What to check first, in order
-
Read codes, freeze frame and misfire counts.
Fix misfires and mixture problems first.
What the data shows: Bank 2 misfire counts, bank 2 fuel trims.
Cost: no cost if you have a scanner
-
Check for exhaust leaks on bank 2.
A leak can fake the result.
What the data shows: Rear sensor reads lean for long periods.
Cost: free to look
-
Compare both banks' rear sensors at steady cruise.
Shows which converter is weak.
What the data shows: The failing side swings; the good side stays calm.
Cost: no cost if you have a scanner
-
Test the bank 2 rear sensor.
A lazy sensor can fake P0430.
What the data shows: It should rise under hard acceleration and fall when coasting.
Cost: $440-$523 at a shop (Oxygen sensor replacement, RepairPal)
-
Replace the bank 2 converter last.
Expensive, and it fails again if the cause remains.
What the data shows: Catalyst monitor completes and the code stays away.
Cost: $2,280-$2,480 at a shop (Catalytic converter replacement, RepairPal)
Is it safe to drive?
Drive normally - check soon
Yes, for now. It is an emissions fault.
Like P0420, the car drives normally and nothing dramatic happens if you keep using it. It fails emissions tests until fixed. Fix any misfire, rich mixture or oil burning before a new converter goes in, or the new one fails the same way.
Stop driving and get help if
- The check engine light flashes.
- The engine shakes or loses power.
- You hear a loud rattle underneath.
What it costs
| Repair | Typical cost |
|---|---|
| Check engine light diagnosis (shop)RepairPal, updated September 3, 2026 | $125-$183 |
| Exhaust manifold gasket replacementRepairPal, updated September 3, 2026 | $417-$596 |
| Oxygen sensor replacementRepairPal, updated September 3, 2026 | $440-$523 |
| Catalytic converter replacementRepairPal, updated September 3, 2026 | $2,280-$2,480 |
National averages for the full job at a shop, parts and labor, from RepairPal (updated September 3, 2026). Your price depends on the car and the area. Many of the first checks on this page cost nothing with a scanner. CarMD found the average check engine repair in 2025 was $554, from more than 39 million US vehicles. Catalytic converter replacement was CarMD's number 1 check engine repair in 2025, at an average of $1,511. Oxygen sensor replacement was number 2, at an average of $287. CarMD averages come from a different method (repairs reported by its users), so they can sit below RepairPal's shop estimates. RepairPal notes that catalytic converters are covered by a federally required 8-year or 80,000-mile warranty from the carmaker. On a newer car, ask the dealer before you pay.
Sources for the notes: CarMD 2026 Vehicle Health Index (press release, April 22, 2026); RepairPal: P0420 code page (federal converter warranty).
Can I clear it? Will it come back?
Clearing resets readiness. The catalyst monitor can take several days to run, and P0430 returns if the converter is still weak.
Will it fail an emissions test?
Yes, in most areas with OBD emissions testing, a lit check engine light fails the test.
Carmaker notes
Service bulletins and warranty extensions that name this code. Ask a dealer to check your VIN.
-
GM 2012-2013 Equinox and Terrain 2.4L
GM Special Coverage N192287100 (October 2020) covers catalytic converter and oxygen sensor wear caused by oil consumption, for 10 years or 150,000 miles.
GM N192287100 via NHTSA static.nhtsa.gov
-
Honda 2016-2017 Pilot, 2017 Ridgeline, 2018 Odyssey
Honda bulletin 20-100 (February 2021): engine software may read a good converter as worn, and injector wear can cause misfires. It covers P0420 and P0430 among other codes, for 10 years or 150,000 miles.
Honda 20-100 via NHTSA static.nhtsa.gov
-
Ford 2018-2020 F-150 2.7L EcoBoost, 2020-2021 Expedition and Navigator
Ford bulletin 22-2260 (January 2023): P0420 or P0430 may come from high sulfur in the fuel. The fix is to de-sulfate the converters, not replace them.
Ford TSB 22-2260 via NHTSA static.nhtsa.gov
-
Toyota 2022-2023 Tundra and Tundra hybrid, 2023 Sequoia hybrid
Toyota bulletin T-SB-0030-23 (June 2023): P0174 with P0430. The fix replaces the left No. 2 fuel delivery pipe and the left catalytic converter.
Toyota T-SB-0030-23 via NHTSA static.nhtsa.gov
Related codes
Also related, no guide yet: P0156, P0157, P0158.
How Obie handles P0430
Obie compares the rear sensors on both banks and the fuel trims, and tells you which cheap causes to rule out before a converter. Obie is part of ScanMyCar Pro. Codes and live sensors are free.
Questions people ask
What is the difference between P0420 and P0430?
P0420 is the bank 1 converter, P0430 is bank 2. The causes and checks are the same.
Can I drive with P0430?
Yes, for now. Fix it before your emissions test, and sooner if there are misfires.
Should I replace both converters?
Only if both test bad. If P0420 is set too, look for a shared cause first.
Sources
- RepairPal: P0430 code page repairpal.com
- RepairPal: Check engine light diagnosis (shop) (updated September 3, 2026) repairpal.com
- RepairPal: Exhaust manifold gasket replacement (updated September 3, 2026) repairpal.com
- RepairPal: Oxygen sensor replacement (updated September 3, 2026) repairpal.com
- RepairPal: Catalytic converter replacement (updated September 3, 2026) repairpal.com
- CarMD 2026 Vehicle Health Index (press release, April 22, 2026) prnewswire.com
- GM N192287100 via NHTSA static.nhtsa.gov
- Honda 20-100 via NHTSA static.nhtsa.gov
- Ford TSB 22-2260 via NHTSA static.nhtsa.gov
- Toyota T-SB-0030-23 via NHTSA static.nhtsa.gov
- Texas DPS emissions testing FAQ dps.texas.gov
- Arizona myazcar.com: OBD and the check engine light myazcar.com
- RepairPal: P0420 code page (federal converter warranty) repairpal.com
A guide, not a diagnosis. This page describes what P0430 generally means across OBD2 cars. What is actually wrong with your car depends on its live data and its history, and any repair decision deserves a proper diagnosis, whether that is you with a scanner or a professional with a lift.
