O2 Oxygen Sensor Upstream Downstream for Toyota Highlander (2008-2010) 3.5L

Direct-Fit Upstream & Downstream O2 Oxygen Sensor Kit for 2008-2010 Toyota Highlander (XU40)

What it Does: This matched 4-piece upstream and downstream oxygen sensor kit monitors pre- and post-catalyst exhaust oxygen levels on the 2008-2010 Toyota Highlander (XU40) 2GR-FE 3.5L V6 to maintain closed-loop fuel trim precision and catalytic efficiency.

The Stock Toyota Highlander Sensor Degradation

On the XU40 chassis with the 2GR-FE 3.5L V6, factory oxygen sensors endure severe thermal cycling and exhaust soot buildup at the manifolds. Over high mileage, internal ceramic elements suffer micro-fractures while heater coils burn out from sustained heat soak. Sluggish voltage switching then skews ECU fuel trims and triggers fault codes including P0031, P0051, P0138, or P0420/P0430.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light / DTCs: Stored heater or response faults like P0031, P0051, P0138, or catalyst codes P0420/P0430 from lazy sensor switching.
• Fuel Trim Instability: Erratic air-fuel feedback forces rich or lean compensation, causing rough cold starts and throttle hesitation.
• Economy & Emissions Loss: Stuck closed-loop trims increase fuel consumption and prevent OBD-II readiness monitors from setting.

The Matched 4-Sensor Direct-Fit Solution

This 4-piece kit replaces all upstream and downstream sensors simultaneously using stainless steel housings and double-layered shields engineered to resist moisture and thermal shock. Precision ceramic elements ensure rapid heater light-off and stable voltage output across the operating range. Interchanging with OEM numbers 234-9022, 234-9008, 234-4509, and 234-4149, each sensor features factory-length harnesses and weatherproof connectors for zero-splice installation.

What's Included

• 2 Upstream Oxygen Sensors
• 2 Downstream Oxygen Sensors

Technical Specifications

Compatibility

• 2008-2010 Toyota Highlander 3.5L (Confirm engine before ordering)

Frequently Asked Questions & Fitment Warnings

Does this fit the XU40 Highlander?

Yes. This is a direct fit for the 2008-2010 Toyota Highlander equipped with the 2GR-FE 3.5L V6 engine. Excludes 2.7L 4-cylinder and 3.3L Hybrid models; confirm engine before ordering.

Will this clear P0031, P0138, or P0420/P0430 codes?

Yes, when triggered by worn sensors. Replacing all four units (234-9022, 234-9008, 234-4509, 234-4149) restores heater resistance and ECU feedback, though a damaged catalyst substrate still triggers P0420/P0430.

Do these sensors require wire splicing?

No. Each sensor features factory-style plug-and-play connectors and OEM-length harnesses; coat threads lightly with anti-seize only and torque to factory spec.

The Toyota Precision Standard

Built for the XU40 platform, this matched 4-sensor kit restores factory closed-loop ECU precision and CEL-free emissions compliance. Clean Bank 1 and Bank 2 lambda telemetry ensures consistent fuel economy and reliable catalytic monitoring.