P0171 on Nissan: How to Diagnose & Fix

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. A Nissan dealer can perform an oil consumption test; if the engine fails it while under warranty, Nissan may authorize repairs.

The Z32 Twin Turbo has over 100 vacuum hoses that deteriorate with age, causing a cascade of problems including boost leaks, erratic idle, failed boost transitions, and check engine lights. The rubber hoses become hard and brittle after 25+ years, cracking and splitting. The complex vacuum system controls boost, EGR, HVAC, and fuel pressure regulation. A single cracked hose can cause multiple symptoms.

Repeated heat cycles — especially severe on the Twin Turbo, where the manifolds also carry the turbochargers — cause the Z32's exhaust manifold studs to stretch and snap, and the manifolds themselves to warp. Broken studs let the gasket blow out, producing the classic exhaust tick on cold start and acceleration, and on turbo cars the pre-turbine leak costs boost response. Extracting broken studs in the cramped bay (the passenger side is notoriously inaccessible) is labor-intensive, which is why so many cars are sold with studs already missing; RepairPal documents the warp-and-broken-stud pattern for the 300ZX with manifold replacement averaging about $1,190-$1,329.

A common first-gen Frontier issue is broken exhaust manifold studs, especially on the VG33E/VG33ER V6. Heat cycling warps the manifold and stresses the studs until one or more snap, creating a ticking exhaust leak that is loudest on cold start. Owners often mistake it for valvetrain noise, but the sound usually fades somewhat as the manifold heats up and expands.

The VG30E and VG33E exhaust manifolds warp slightly over years of heat cycling, which snaps the manifold-to-head studs (the rear stud on the passenger/right bank is the most common casualty). This creates an exhaust leak with a characteristic ticking/tapping that is loudest on a cold start and quiets as the engine warms and the manifold expands to close the gap. Nissan acknowledged the problem in a Technical Service Bulletin and released higher-strength replacement studs.

P0174 references Bank 2, which physically exists only on the Altima's 3.5L VQ35DE V6 (the inline-4 has no Bank 2), so this code points specifically at the V6 rear cylinder bank. It nearly always appears together with P0171, and that pairing is the diagnostic tell: a lean condition on BOTH banks is caused by something common to the whole engine rather than one injector. On the VQ35DE the usual causes are shrunken/hardened intake manifold and plenum gaskets that develop vacuum leaks, a cracked PCV or intake hose, or a dirty MAF sensor under-reporting airflow to both banks. Nissan issued ECM-reprogram guidance (TSB NTB19-030) for lean-code complaints on 2016-2018 V6 Altima/Maxima where fuel trims are borderline, so a software update can be part of the fix after mechanical leaks are ruled out.

First-generation (2000-2004) Xterras with the 3.3L VG33E/VG33ER V6 commonly crack the passenger-side (right) exhaust manifold over time due to heat cycling. A Nissan TSB acknowledged the issue. A cracked manifold produces a ticking/exhaust leak noise that is loudest on cold start, can trigger the check-engine light, and can affect downstream oxygen-sensor readings and performance.

On 2022+ Rogues equipped with the 1.5L KR15DDT variable-compression turbo engine, owners have reported rough idle, gasoline/fuel odor, hesitation, and check-engine lights tied to crankcase ventilation or related air-fuel control issues. These complaints are distinct from outright transmission concerns and appear in owner forums and complaint databases as the newer engine accumulated mileage. In some cases, the issue presents as drivability problems without obvious external leaks.

The MR16DDT 1.6 DIG-T is a direct-injected engine, so fuel never washes the back of the intake valves. Combined with PCV oil vapor routed into the intake tract, hard carbon deposits accumulate on the valve stems and seats, typically becoming symptomatic between roughly 60,000 and 100,000 miles. Deposits disrupt airflow and prevent valves from sealing, producing cold-start rough idle, a shaking/shuddering idle that smooths out under load, hesitation and eventually stored misfire codes. Owners on Juke Forums repeatedly report chasing coils and injectors before finding the valves coked. The problem is aggravated by short-trip driving and extended oil-change intervals.

The revised VQ35DE "Rev-Up" engine (2005-2006 350Z) is notorious for excessive oil consumption, often burning 1 quart every 1,000-2,000 miles. Nissan covered it in technical bulletin NTB07-088 (later revised as NTB07-088d) for 2005 Track and 35th Anniversary manual cars and 2006 manual cars: after an oil-consumption test, the remedy for excessive consumption was replacing the short engine assembly, and some owners report the replacement engine also used oil. 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).