O2 Oxygen Sensor Upstream Downstream for Infiniti FX35 M35 (2007-2008) 3.5L

Direct-Fit O2 Oxygen Sensor Kit for 2007-2008 Infiniti FX35,M35 (S50/Y50)

What it Does: This 4-piece upstream and downstream oxygen sensor kit monitors exhaust air-fuel ratios and converter efficiency on 2007-2008 Infiniti FX35 (S50) and M35 (Y50) VQ35DE 3.5L V6 models.

The Stock Infiniti FX35,M35 Sensor Failure

On high-mileage S50 and Y50 chassis models equipped with the VQ35DE 3.5L V6, extreme exhaust heat soak and thermal cycling degrade factory zirconia ceramic elements and internal heater circuits. Carbon soot and oil blow-by foul upstream wideband tips, causing sluggish voltage switching and skewed fuel trims. Failing downstream heaters trigger false converter faults and force rich open-loop operation, accelerating catalytic degradation.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light / DTCs: Triggers codes like P0031/P0051 (heater circuit), P2A00/P2A03 (A/F range), and P0138/P0158.
• Sluggish Closed-Loop Response: Delayed voltage transitions cause rough idle, hesitation, and erratic fuel trim corrections.
• Poor Fuel Economy & Emissions Failure: Rich fail-safe fueling fouls spark plugs and fails smog tests.

The Direct-Fit Ceramic Oxygen Sensor Solution

Replacing all four positions as a matched set restores Bank 1 and Bank 2 telemetry using OE-equivalent 234-5061 upstream and 234-4380 downstream sensors. Each unit features laser-welded stainless housings, porous PTFE membranes, and thermal-shock-resistant zirconia ceramic elements for rapid light-off. Factory-length shielded harnesses and keyed OEM-style connectors allow plug-and-play installation into stock exhaust bungs without splicing for reliable long-term output.

What's Included

• 2 Upstream Oxygen Sensors (234-5061)
• 2 Downstream Oxygen Sensors (234-4380)

Technical Specifications

Compatibility

• 2007-2008 Infiniti FX35 3.5L (S50 Chassis)
• 2007-2008 Infiniti M35 3.5L (Y50 Chassis)

Frequently Asked Questions & Fitment Warnings

Does this fit the S50/Y50 FX35,M35?

Yes. Direct fit for 2007-2008 Infiniti FX35,M35 with the VQ35DE 3.5L V6. Excludes 4.5L V8 FX45/M45 trims; confirm engine before ordering.

Will this clear P2A00, P0138, or P0031 codes?

Yes. Replacing failed sensors clears sensor-related P2A00/P2A03, P0138/P0158, and heater DTCs after a drive cycle, assuming no exhaust leaks exist.

Are connectors pre-terminated for direct installation?

Yes. All four sensors feature OEM plugs; apply anti-seize to threads only and torque to factory spec.

The Infiniti Precision Standard

Built for high-temperature VQ-series exhaust environments, this matched kit restores closed-loop fuel accuracy and emissions compliance. Expect CEL-free operation and balanced cylinder-bank telemetry.