P0420 on Nissan: How to Diagnose & Fix

The 2004-2015 Titan VK56DE engine is prone to exhaust manifold bolt failure due to thermal cycling. The bolts break or the manifold warps, causing an exhaust leak that sounds like a ticking noise on cold start. The issue affects both banks but the driver's side (bank 1) is more common. Broken bolts can be extremely difficult to extract.

The 2009-2014 Murano VQ35DE 3.5L V6 engine can consume excessive amounts of oil, sometimes 1 quart every 1,000-2,000 miles. The issue is caused by worn piston rings and valve stem seals. Nissan TSB NTB13-076 addresses the oil consumption test procedure. If the engine fails the consumption test, Nissan may authorize repairs under warranty.

The Murano VQ35DE is prone to premature catalytic converter failure, often between 80,000-120,000 miles. The Bank 1 (firewall side) converter typically fails first. Contributing factors include the engine's tendency toward oil consumption, which poisons the catalyst, and heat soak from the converter's close proximity to the engine. Failed converters trigger emission codes and can cause reduced power and failed emissions tests.

The VQ35DE 3.5L V6 in the 2016-2023 Maxima can develop excessive oil consumption, burning 1 quart every 1,500-3,000 miles. The issue is more prevalent in higher-mileage examples and is caused by piston ring wear and PCV system issues. Low oil levels can damage the catalytic converters.

The Maxima VQ35DE is known for premature catalytic converter failure, particularly the Bank 1 (front) converter. Failure typically occurs between 80,000-120,000 miles. The catalyst substrate deteriorates, often triggered by oil consumption issues inherent to the VQ35DE, rich running conditions, or age. The pre-cat (close-coupled converter near the exhaust manifold) fails more often than the underbody converter due to extreme heat exposure.

The NV200 is one of the most targeted vehicles for catalytic converter theft due to its higher ground clearance and easily accessible exhaust system. Muffler shops report seeing 2-10 NV200s per week with stolen converters. Thieves can remove the catalytic converters in under two minutes. The NV200 has two catalytic converters, and often both are stolen. Replacement costs are significant and the vehicle cannot pass emissions inspection without them.

Early 350Z models (2003-2006) with the pre-revision VQ35DE engine consume oil excessively, often 1 quart every 1,000-2,000 miles. The issue is caused by thin piston rings and a catalytic converter design that pulls oil through the PCV system. Nissan revised the engine in 2005 (Rev-Up) and again in 2007 (HR) to address this, but the early DE engines continue to burn oil. High-RPM driving accelerates consumption.

The VQ35DE runs close-coupled pre-catalysts in the exhaust manifolds. When the ceramic substrate breaks down — accelerated by an engine already consuming oil, by misfires, or by heat — the fine abrasive debris can be drawn back into a cylinder during valve overlap and at high rpm, where it scores the bore and wrecks the rings. The result is not a converter repair but a rebuilt or replaced engine, and it is the single most consequential thing to check before buying an early Z. It compounds the known VQ35DE oil-consumption problem: burning oil poisons the cats, and dying cats then kill the engine. Owner reports cluster well into six figures of mileage. The 2007-2009 VQ35HR uses a different exhaust manifold/catalyst arrangement and does not carry this reputation.

The revised VQ35DE "Rev-Up" engine (2005-2006 350Z, also known as the VQ35DE Rev-Up) is notorious for excessive oil consumption, often burning 1 quart every 1,000-2,000 miles. The issue is caused by defective galley gaskets (oil passage o-rings) that leak oil internally. The standard VQ35DE (2003-2004) and the later VQ35HR (2007-2009) do not suffer from this issue to the same degree. Nissan acknowledged the problem but did not issue a recall. The Rev-Up engine can be identified by its higher redline (7,000 vs 6,600 RPM).

A recurring Versa complaint across both the 1.6L HR16DE and the 1.8L MR18DE is oil disappearing with no drips on the driveway and no visible smoke. The two mechanisms owners and mechanics land on are oil-control ring coking — the low-tension rings carbon up in their grooves and stop scraping — and worn valve guides/stem seals letting oil down the intake ports at idle and on overrun. The MR18DE compounds this with a plated aluminum bore rather than iron liners; where the plating is imperfect the bore wears and consumption climbs early. Forum reports span the whole range from a mild 200 ml per 1,500 km on a high-mileage car (arguably normal) to genuinely defective cases burning a quart every 200 miles by 75,000 miles. The real danger is not the oil cost: the Versa has no low-oil-level warning, only a pressure light that comes on far too late, so owners who trust the change interval run the engine dangerously low and destroy bearings or seize the engine.

The 4.0L VQ40DE Frontier is a repeat offender for catalyst efficiency codes, typically appearing somewhere past 100,000 miles as P0420 (Bank 1) or P0430 (Bank 2), often both. The converter is usually a victim rather than the root cause: unburned fuel from a misfire, an over-rich condition, or oil consumption cooks the substrate until the downstream oxygen sensor stops seeing a difference across the brick. Club Frontier threads repeatedly pair P0300-series misfire codes with P0420/P0430 on the same truck, and the earliest 2005-2006 V6 trucks are the most frequently discussed. Because the converters are close-coupled to the exhaust manifolds, a broken manifold stud or a manifold leak upstream will also drive the codes. In the worst documented cases the ceramic substrate breaks down and gets drawn back through the exhaust valves during overlap, contributing to cylinder wall scoring and oil consumption - so a converter code on a high-mile VQ40DE should never be dismissed as an emissions annoyance.

The exhaust manifold on the Altima is prone to developing cracks from repeated heat cycling, producing a ticking/tapping noise from the front of the engine that is loudest on cold start (and often quiets as the metal expands and the crack closes), along with an exhaust smell and a leak ahead of the catalyst. On many 2.5L model years the manifold is integrated with the front catalytic converter, so a cracked manifold and a P0420 catalyst fault often go together and make replacement more involved.

On many 2.5L QR25DE Altimas, the pre-catalytic converter material can deteriorate and be drawn back into the engine during valve overlap, scoring cylinder walls and accelerating oil consumption. Owners report needing to add oil frequently, loss of compression, rough running, and in severe cases complete engine failure. This issue is widely discussed in owner communities and tied to Nissan service information addressing catalyst and ECM updates on affected 2.5L cars.

P0420 (catalyst system efficiency below threshold) is one of the most common check-engine codes on the 2.5L Altima. The integrated exhaust-manifold/catalyst on these cars loses efficiency as the substrate degrades, the downstream oxygen sensor begins tracking the upstream sensor, and the ECM sets P0420. Untreated upstream causes — misfires, oil consumption, or a failing O2 sensor — accelerate catalyst breakdown. Because the front (main) catalyst is integrated with the exhaust manifold on many model years, replacement is costlier than a typical under-car converter. Nissan ran emissions recall PC717 on certain 2018 Altimas (QR25DE) that replaced the exhaust manifold/three-way catalyst assembly and two exhaust sensors at no charge.

The R52 Pathfinder with the VQ35DE engine experiences premature catalytic converter failure, often between 80,000-120,000 miles. The catalytic converters can become clogged or the catalyst substrate breaks down, triggering P0420/P0430 codes. Contributing factors include the CVT issues that can cause rich running conditions, oil consumption, and short trip driving. The Pathfinder uses two catalytic converters (Bank 1 and Bank 2).

The cast iron exhaust manifolds on VQ35DE and VQ40DE equipped Pathfinders are prone to cracking due to thermal cycling. The passenger side manifold is most commonly affected. Cracks cause an exhaust leak that produces a ticking noise on cold starts that may diminish as the engine warms up. Over time the crack worsens and the leak becomes constant.

The catalytic converter degrades or clogs over time (often accelerated by a rich fuel condition from a failing upstream O2 sensor, MAF sensor, or worn plugs), setting a P0420 catalyst-efficiency check-engine light and causing sluggish acceleration and rattling from a broken internal substrate. Separately, the Rogue's converter is a known theft target on some model years; theft leaves a very loud exhaust and a P0420/P0430 code. This is distinct from the already-covered exhaust flex-pipe/heat-shield rattle.

In rust-belt use especially, owners report the front exhaust flex section and attached heat shields corroding, leading to exhaust leaks, metallic rattles, and louder engine noise under acceleration. Some complaints describe a buzzing or tinny rattle at idle that is traced to loose converter or pipe heat shielding rather than an internal engine problem. This issue is repeatedly discussed in owner forums and independent repair databases for first-generation Rogue vehicles.

The KA24E engine in the Stanza develops oil leaks from the valve cover gasket, oil pan gasket, rear main seal, and front crank seal as the gasket materials age and harden. The most common and visible leak is from the valve cover gasket, which drips oil onto the exhaust manifold causing a burning oil smell. The rear main seal leak is more serious and labor-intensive to repair. These leaks are typical of aging KA24E engines across all Nissan applications.

The VK56DE V8 in the first-gen Armada is notorious for cracked exhaust manifolds. Both driver and passenger side manifolds develop cracks from thermal cycling, causing an exhaust leak that sounds like a ticking noise on cold start. The cracks worsen over time and can cause check engine lights from O2 sensor readings being affected by the leak. The catalytic converters can also be damaged by unmetered air entering the exhaust stream.

The TA60 runs close-coupled converters bolted to the manifolds plus secondary converters downstream. Owners repeatedly report the ceramic substrate in an upstream converter breaking apart, at which point the loose material blows downstream and packs the secondary converter, choking the exhaust. Symptoms progress from a P0420/P0430 efficiency code to a rattle from the exhaust, then to a truck that will not pull, runs hot, and feels like it has lost half its power because it cannot exhale. Because the same codes are also set by lazy oxygen sensors, plenty of owners replace sensors first and are surprised when the codes come back.

The B17 and B18 Sentra with the MR20DD engine is prone to premature catalytic converter failure, often before 100,000 miles. The converter substrate breaks down, triggering P0420 efficiency codes. Contributing factors include the direct injection engine's tendency to produce more particulates, short trip driving cycles that prevent the converter from reaching full operating temperature, and catalytic converter theft (the Sentra's low ground clearance makes it an easy target).

The KA24DE engine in the 240SX is known for developing oil leaks from multiple locations as gaskets age. The rear main seal is the most problematic, leaking oil onto the clutch (manual trans) or flex plate (automatic). Valve cover gaskets also harden and leak, dripping oil onto the exhaust manifold. The oil pan gasket and front crank seal are additional common leak points. These leaks are exacerbated by age and the high operating temperatures of the KA24DE.