P0430 on Nissan

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.

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 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 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 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 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 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 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.

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 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 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.

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.