P0430 on Toyota: How to Diagnose & Fix
Catalyst System Efficiency Below Threshold (Bank 2)
6 Toyota models · 6 documented issues · $200-$3,000 repair
P0430 on Toyota by model: symptoms, diagnosis and fix
Toyota Tundra V8 engines are prone to exhaust manifold cracking, particularly on the driver side where the air injection tube weld enters the manifold. Additionally, exhaust manifold bolts can corrode and break, causing exhaust leaks. The ticking noise is most noticeable at cold startup.
Common Symptoms
- Ticking noise at cold startup
- Exhaust smell in cabin
- Hissing sound from engine bay
- Reduced fuel economy
- Failed emissions test
How to Fix
Repair options include welding cracks (temporary), replacing with OEM manifolds ($800-$1,500), or upgrading to aftermarket headers ($1,000-$2,500). Broken bolts require extraction. Total repair costs range from $500 to $3,000+.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Toyota 17104-50220 genuine right exhaust manifold
replace a test-confirmed cracked or warped right 4.7L exhaust manifold Fitment/availability: Right-side 4.7L 2UZ-FE Tundra branch; use only after VIN, engine, production date, emissions and secondary-air configuration are confirmed Fitme…
- Toyota 17105-50210 genuine left exhaust manifold
replace a test-confirmed cracked or warped left 4.7L exhaust manifold Fitment/availability: Left-side 4.7L 2UZ-FE Tundra branch; use only after VIN, engine, production date, emissions and secondary-air configuration are confirmed Fitment…
- Toyota 17104-38011 genuine right exhaust manifold
replace a test-confirmed cracked or warped right 5.7L exhaust manifold Fitment/availability: Right-side 5.7L 3UR-FE/3UR-FBE branch; the page supersedes 17104-38010 to 17104-38011, and VIN, emissions and secondary-air configuration still …
- Toyota 17105-38011 genuine left exhaust manifold
replace a test-confirmed cracked or warped left 5.7L exhaust manifold Fitment/availability: Left-side 5.7L 3UR-FE/3UR-FBE branch; the page supersedes 17105-38010 to 17105-38011, and VIN, emissions and secondary-air configuration still re…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- TipDIY repairs can save significantly - dealer charges $800-$1,500 but DIY costs are typically 50-70% less
- TipConsider OEM parts for critical components like sensors and electrical parts - aftermarket can be unreliable
- TipGet a proper diagnosis before replacing parts - similar symptoms can have different causes
Sources for this issue (1)
A very common Highlander check-engine complaint is P0420 (Catalyst Efficiency Below Threshold, Bank 1) and its Bank 2 twin P0430. The downstream oxygen sensor readings track the upstream sensor too closely, indicating the catalytic converter is no longer scrubbing exhaust efficiently. Root causes are an aged/failed converter, a lazy air-fuel or downstream O2 sensor, or an exhaust leak upstream. It fails emissions inspections and is a frequent search/complaint across model years.
Common Symptoms
- Check engine light with P0420 and/or P0430
- Reduced fuel economy
- Sulfur/rotten-egg exhaust smell
- Emissions test failure
- Occasional mild hesitation
How to Fix
Diagnose before replacing: verify no exhaust leaks, check for oil/coolant consumption that poisons the cat, and scope O2/AF sensor switching. If a sensor is lazy, replace it (use Denso/OEM). If the monitor confirms low catalyst efficiency, replace the affected catalytic converter (California/CARB vehicles require a CARB-compliant unit). Clear codes and re-run readiness monitors.
Sources for this issue (2)
High-mileage XL20 Siennas commonly set P0420 (Bank 1) and sometimes P0430 (Bank 2) for catalyst efficiency below threshold. On this V6 layout Bank 1 is the rear (firewall) bank and Bank 2 the front, and the van carries four sensors: two upstream air/fuel ratio sensors and two downstream heated oxygen sensors. The most frequent real cause is a lazy downstream sensor whose switching has slowed with age, not a dead converter - but shops routinely quote catalytic converter replacement first, which on this van is a four-figure job. Exhaust leaks upstream of the rear sensor and unresolved misfires also set the code.
Common Symptoms
- Check engine light with catalyst efficiency code
- Slightly reduced fuel economy
- Failed state emissions inspection
- No drivability symptom in many cases
How to Fix
Before replacing a converter, graph the downstream sensor on a scan tool - a healthy rear sensor should sit relatively flat around 0.6-0.7V, while a sensor that mirrors the upstream switching is worn out. Also smoke-test or listen for exhaust leaks at the manifold and flange gaskets and clear any misfire codes first. A Denso or OEM downstream sensor is a few hundred dollars installed versus $1,200-$2,200 for the rear manifold converter, which sits against the firewall and is the labor-intensive one. No recall exists, though the converter may be covered under the federal 8-year/80,000-mile emissions warranty on vehicles still in that window.
Sources for this issue (3)
The cast iron exhaust manifolds on the 2001-2007 Sequoia 4.7L V8 develop cracks from repeated thermal cycling. The cracks typically appear at the flange where the manifold bolts to the cylinder head or between the runner tubes. A cracked manifold causes an audible exhaust leak (ticking noise on cold start that fades as the manifold expands when hot), a faint exhaust smell near the engine bay, and can eventually trigger a check engine light for catalyst efficiency if exhaust gases bypass the catalytic converter.
Common Symptoms
- Ticking or tapping noise from engine on cold start
- Exhaust noise that fades as engine warms up
- Exhaust smell near engine bay or cabin
- Check engine light for catalyst efficiency
- Visible cracks on exhaust manifold surface
- Soot stains around manifold flange area
How to Fix
Replace the cracked exhaust manifold ($300-$600 per side for parts). Both sides should be inspected as cracking often affects both manifolds. The exhaust manifold studs frequently break during removal due to corrosion — budget for stud extraction or replacement ($100-$200 extra). Total repair with gaskets and hardware runs $800-$1,500 per side at a shop. Aftermarket stainless steel headers ($400-$800 per side) are a popular upgrade that resists cracking. Always replace the manifold gaskets during the repair.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Toyota 17104-50151 right exhaust manifold subassembly
replace a confirmed cracked right exhaust manifold on the matching early-design branch Fitment/availability: Right-side early-design catalog branch shown for 2001-2005 Sequoia; confirm VIN, production date and air-injection configuration…
- Toyota 17105-50151 left exhaust manifold subassembly
replace a confirmed cracked left exhaust manifold on the matching early-design branch Fitment/availability: Left-side early-design catalog branch shown for 2001-2005 Sequoia; confirm VIN, production date and air-injection configuration b…
- Toyota 17104-50200 right exhaust manifold subassembly
replace a confirmed cracked right exhaust manifold on the matching late-design branch Fitment/availability: Right-side late-design catalog branch shown for 2004-2007 Sequoia; confirm VIN, production date and air-injection configuration b…
- Toyota 17105-50190 left exhaust manifold subassembly
replace a confirmed cracked left exhaust manifold on the matching late-design branch Fitment/availability: Left-side late-design catalog branch shown for 2004-2007 Sequoia; confirm VIN, production date and air-injection configuration bef…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Owner tips & cautions
- WarningSoak the exhaust manifold studs with penetrating oil (PB Blaster) for several days before attempting removal. Broken studs are extremely common on these engines and add significant cost to the repair.
Sources for this issue (2)
Owners of high-mileage fourth-generation 4Runners with the 4.0L V6 report catalyst efficiency codes P0420 and P0430; in one case only replacing the exhaust-manifold catalytic converters cleared them. It affects 2003-2009 4Runners with the 4.0L 1GR-FE V6. Owners reported the codes on a 2004 at 150,000 miles, a 2005 at 185,000 miles, a 2007 SR5 at about 180,000 miles and a 2008 at about 320,000 miles.
Common Symptoms
- Check engine light with catalyst codes P0420 and P0430
- Catalyst code comes back after oxygen sensors are replaced
How to Fix
Have a technician confirm the converters have failed before replacing them, for example by checking for misfires, exhaust leaks and downstream oxygen sensor readings. One owner reports that a cat cleaner and new oxygen sensors did not clear the codes.
Sources for this issue (2)
Owners of second-generation Tacomas with the 4.0L 1GR-FE V6 report code P0430 (Bank 2 catalyst efficiency below threshold), in several reports blamed on failed catalysts built into the exhaust manifolds. It affects 2005-2015 Tacomas with the 4.0L 1GR-FE V6; the owner reports linked here include 2005 and 2013 trucks.
Common Symptoms
- Check engine light with code P0430
- Code keeps returning after new converters while a misfire is present
How to Fix
Have a technician rule out misfires, exhaust leaks and the oxygen sensors before replacing a converter; in one owner report linked here, P0420/P0430 kept returning after new converters while a misfire was still present. Whether the federal emissions warranty covers a converter depends on the truck's age and mileage; ask a dealer.
Call to confirm they can assess your vehicle and perform the stated work. Search results do not confirm qualification, eligibility or coverage.
Sources for this issue (3)
P0430 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0430 mean on a Toyota?
P0430 stands for "Catalyst System Efficiency Below Threshold (Bank 2)." This code means the catalytic converter on Bank 2 (the side of the engine that does not contain cylinder #1) is not reducing emissions as effectively as it should. The computer compares the readings of the oxygen sensors before and after the converter; if the downstream sensor's signal starts mirroring the upstream one, it indicates the converter is no longer storing and processing oxygen properly. This usually points to a worn-out or damaged catalytic converter, but it can also be caused by faulty sensors or upstream engine problems that have poisoned the converter. The car will generally still run, but it will fail an emissions test. On Toyota it is documented across 6 models: Tundra, Highlander, Sienna, Sequoia, 4Runner, Tacoma.
What are the most common causes of P0430?
The most common causes of P0430 are: Worn-out or failed catalytic converter (Bank 2), Faulty downstream (post-cat) oxygen sensor, Faulty upstream oxygen sensor giving bad data, Exhaust leak near the converter or sensors, Engine misfire or oil/coolant burning that damaged the catalyst, Running too rich or too lean over time, Aftermarket or non-compliant catalytic converter. The specific cause varies by vehicle.
How much does it cost to fix P0430 on a Toyota?
Published repair estimates on Toyota range from $200 to $3,000 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
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Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.