P0420 on Nissan

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.

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).

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.

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.

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 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 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 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).

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 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 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 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 Versa experiences premature catalytic converter failure and is a frequent target for catalytic converter theft due to its low ground clearance providing easy access. The converter substrate degrades over time, triggered by engine running conditions and short trip driving. Even when not stolen, the converter often fails between 80,000-120,000 miles. The combination of a common theft target and premature failure makes this one of the most impactful Versa issues.