P0420 on Toyota

The 2UZ-FE V8 in 4th-generation 4Runners is known for exhaust manifold cracking, especially as the vehicle ages and heat cycles accumulate. Owners usually hear a cold-start ticking or tapping from the engine bay that quiets somewhat as the manifolds warm up, and some eventually get catalyst-efficiency or oxygen-sensor-related codes due to exhaust leaks. The issue is well documented in owner forums and repair shops because manifold replacement is labor-intensive and often expensive on both banks.

Many 2007-2011 4-cylinder Camrys with the 2AZ-FE developed excessive oil consumption, often requiring a quart every 1,000-1,500 miles or worse. Toyota acknowledged the condition in service campaigns and TSBs tied to piston and oil-control ring design, and owners commonly reported low-oil warnings, engine knock on startup, and eventual catalyst damage if the condition was ignored. The problem is especially well documented on higher-mileage vehicles but can appear earlier depending on maintenance history.

The 1ZZ-FE engine used in 2000-2005 Celica GT models is notorious for excessive oil consumption, often burning 1 quart every 1,000-1,500 miles. The root cause is poorly designed oil control piston rings that allow oil to pass into the combustion chamber. Toyota revised the piston ring design in later production runs but never issued a recall for the Celica. High-mileage examples may consume even more oil, leading to catalytic converter damage from oil contamination.

The pre-catalytic converter (integrated into the exhaust manifold) on 2000-2005 Celicas can disintegrate internally, sending ceramic fragments back into the engine through exhaust valve overlap. This causes scoring of cylinder walls and accelerated engine wear. The pre-cat material breaks down from age and heat cycling. Removing or gutting the pre-cat and installing a proper downstream catalytic converter is the standard community fix, though emissions compliance varies by state.

The 1ZZ-FE engine used in many 2000-2008 Corollas is widely known for developing excessive oil consumption as piston oil-control rings stick or wear. Owners report needing to add oil between changes, blue smoke on startup or acceleration, fouled plugs, and eventual catalyst damage if the oil-burning is ignored. Toyota issued service information and owner complaints are abundant across NHTSA and enthusiast forums.

The 2.4L FA24 boxer engine in the GR86 consumes oil more than expected, particularly when driven hard on track. Consumption of 1 quart per 2,000-3,000 miles is common. The horizontal cylinder layout and high-RPM operation contribute to oil consumption past the piston rings.

The 3.5L 2GR-FE V6 in 2nd-gen Highlanders consumes oil excessively, often 1 quart per 1,000-2,000 miles. The root cause is piston ring design allowing oil past the rings into the combustion chamber.

The 2.4L 2AZ-FE 4-cylinder in the 2nd-gen Matrix consumes oil excessively due to defective piston ring design, often 1 quart per 1,000-2,500 miles. This is the same issue affecting Camry, RAV4, and other Toyota models with the 2AZ-FE. Toyota extended the warranty under enhancement ZE7.

The third-generation MR2 Spyder (2000-2005) uses the same 1ZZ-FE engine that plagues the Celica and Corolla with excessive oil consumption. The defective piston ring design allows oil to bypass into the combustion chamber. The MR2 Spyder is particularly susceptible because the mid-engine placement and higher operating temperatures can exacerbate oil consumption. Owners should check oil level at every fuel stop.

The pre-catalytic converter on 2000-2005 MR2 Spyders can disintegrate internally, sending ceramic material back into the engine cylinders during exhaust valve overlap. This is the same issue affecting all 1ZZ-FE-equipped Toyotas of this era. The ceramic debris scores cylinder walls and accelerates engine wear. Early removal or replacement of the pre-cat is considered essential preventive maintenance in the MR2 community.

The Paseo's cast iron exhaust manifold is prone to cracking due to thermal cycling, typically developing cracks between cylinders 2 and 3. The crack allows exhaust gases to escape before the catalytic converter, causing a ticking noise on cold starts that may quiet down when warm. The leak can also cause inaccurate O2 sensor readings and a check engine light.

The 3rd generation Prius with the 2ZR-FXE engine consumes excessive oil, often burning 1 quart every 1,000-2,000 miles. The root cause is defective piston rings that do not properly seal against the cylinder walls. Toyota extended the warranty to 10 years/150,000 miles for affected vehicles under a customer support program (ZE7).

The Toyota Prius is the single most targeted vehicle for catalytic converter theft in the United States. The Prius catalytic converter contains higher concentrations of precious metals (palladium, rhodium, platinum) than most vehicles because the hybrid system results in a cleaner-running engine that preserves the catalyst metals. The converter is also easily accessible under the vehicle and can be cut out with a battery-powered reciprocating saw in under 60 seconds. Thieves sell stolen converters for $100-$300 to recyclers who extract metals worth $500+. Gen 2 (2004-2009) and Gen 3 (2010-2015) Prius are the most targeted.

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.

The 3.5L 2GR-FE V6 in 2nd and 3rd generation Siennas can consume 1 quart of oil every 2,000-3,000 miles. Worn piston rings and valve stem seals are the primary causes. The issue is more prevalent in vehicles driven primarily in city stop-and-go conditions where the engine rarely reaches full operating temperature.

The 2.4L 2AZ-FE engine used in the Solara (shared with Camry and RAV4) has a well-documented excessive oil consumption issue. The piston rings do not maintain adequate tension against the cylinder walls, allowing oil to pass into the combustion chambers. Consumption of 1 quart per 1,000-1,500 miles is common. Toyota issued a Limited Service Campaign (LSC ZE7) for some Camry models but Solara coverage has been inconsistent. Running low on oil causes catalytic converter damage and potential engine seizure.

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.

The 2.7L 2AR-FE 4-cylinder in the Venza consumes oil excessively due to defective piston ring design. Consumption of 1 quart per 1,200-2,500 miles is common. Toyota acknowledged the issue with warranty extension ZE7 covering piston ring replacement.