O2 Oxygen Sensor Upstream Downstream for Nissan 350Z (2003-2004) 3.5L

Direct-Fit Upstream & Downstream O2 Oxygen Sensor Kit for 2003-2004 Nissan 350Z (Z33)

What it Does: This 4-piece upstream and downstream O2 oxygen sensor kit monitors pre- and post-catalytic converter exhaust oxygen levels on the 2003-2004 Nissan 350Z (Z33) VQ35DE 3.5L V6 to regulate closed-loop air-fuel ratios and verify catalyst efficiency.

The Stock Nissan 350Z O2 Sensor Failure

Factory oxygen sensors on the Z33 chassis equipped with the VQ35DE 3.5L V6 endure severe thermal cycling, exhaust carbon buildup, and oil vapor contamination inside the dual-bank exhaust manifolds and mid-pipes. Over time, internal ceramic zirconia sensing elements glaze over or fracture from heat soak, while internal heater circuits burn out from resistance spikes. Once response latency increases, the ECM loses accurate stoichiometric fuel trim control, triggering P0135, P0155, or lean/rich fuel trim faults like P0171 and P0174.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light / O2 & Fuel Trim DTCs: Triggered fault codes such as P0130, P0135, P0155, or P0171/P0174 caused by open heater circuits or sluggish sensor voltage switching.
• Erratic Closed-Loop Fueling & Poor Economy: Delayed upstream sensor feedback forces the ECM into rich open-loop default maps, fouling spark plugs and increasing fuel consumption.
• Failed Emissions Inspection & Rough Idle: Compromised downstream monitoring and skewed Bank 1/Bank 2 air-fuel balance cause inconsistent idle quality and elevated tailpipe emissions.

The Direct-Fit 4-Piece Oxygen Sensor Solution

Replacing all four sensors simultaneously restores synchronized Bank 1 and Bank 2 voltage feedback across the Z33 dual-exhaust architecture. Each sensor utilizes a corrosion-resistant stainless steel housing, high-temperature internal heater element, and OE-grade zirconia sensing core engineered to withstand exhaust thermal shock. Pre-terminated factory-style harnesses match OE lengths and connector keying for direct plug-and-play replacement of part numbers 234-4302, 234-4308, 234-4312, and 1A250-24403 without wire splicing.

What's Included

• 2x Upstream Oxygen Sensors
• 2x Downstream Oxygen Sensors

Technical Specifications

Compatibility

• 2003 Nissan 350Z 3.5L
• 2004 Nissan 350Z 3.5L

Frequently Asked Questions & Fitment Warnings

Does this fit the Z33 350Z?

Yes. This is a direct fit for the 2003-2004 Nissan 350Z equipped with the VQ35DE 3.5L V6 engine. Confirm your 3.5L engine before ordering; this kit does not fit 2005-2009 Nissan 350Z models or later VQ35HR dual-intake engines.

Will this clear P0135, P0155, or P0171 codes, and are all four sensors included?

Yes. This matched 4-piece kit includes both Bank 1 and Bank 2 upstream sensors and both downstream sensors to resolve O2 heater circuit faults like P0135/P0155 and slow-response fuel trim codes like P0171 after clearing ECM memory, provided no exhaust leaks or wiring harness damage exist.

Is wire splicing required for installation?

No. All four direct-fit sensors include factory-keyed electrical connectors and OE harness lengths for plug-and-play installation into existing exhaust bungs; clean bung threads with a thread chaser before torquing and avoid getting anti-seize on the sensor tip.

The Nissan Performance Standard

Accurate exhaust oxygen feedback is essential for maintaining combustion efficiency, catalyst health, and crisp throttle response on the Z33 platform. Replacing all four sensors as a matched set keeps Bank 1 and Bank 2 fueling balanced under aggressive street and high-RPM driving loads.