O2 Oxygen Sensor Upstream Downstream for Toyota Highlander (2001-2003) 3.0L

Direct-Fit Upstream & Downstream O2 Sensor Kit for 2001-2003 Toyota Highlander (XU20)

What it Does: This matched upstream and downstream O2 sensor kit monitors exhaust oxygen levels on 2001-2003 Toyota Highlander XU20 1MZ-FE 3.0L V6 models to optimize fuel trim and emissions.

The Stock Toyota Highlander Sensor Failure

Factory oxygen sensors on the XU20 chassis powered by the 1MZ-FE 3.0L V6 endure severe exhaust manifold heat soak and thermal cycling. Over time, internal heater elements frequently burn out, while carbon soot and fuel additives poison the ceramic zirconia sensing element. This sluggish voltage response disrupts closed-loop fuel trims, forcing rich running conditions and triggering ECU fault codes including P1135, P1155, and P0135.

Common Symptoms of a Failing OEM O2 Sensor

• Check Engine Light / DTCs: Stored codes like P1135, P1155, or P0420 from heater burnout or slow response.
• Fuel Trim Instability: Rough cold starts, idle surge, and rich exhaust from skewed air-fuel feedback.
• Compliance & Economy Drop: Reduced fuel mileage and failed emissions tests due to unburned fuel.

The Direct-Fit Planar Zirconia Oxygen Sensor Solution

This matched upstream and downstream kit restores factory response rates using thermal-shock-resistant zirconia elements and laser-welded stainless steel sensor housings. Internal dual-layer porous ceramic protection shields the sensing core from exhaust moisture and soot buildup. Pre-terminated OEM-style harness connectors and anti-seize-compatible threaded bungs provide true plug-and-play installation without splicing wires. Replacing both sensors as a matched set directly replaces OEM numbers 234-9023, 234-4215, 234-9009, and 89467-48011.

What's Included

• 1 Upstream Oxygen Sensor
• 1 Downstream Oxygen Sensor

Technical Specifications

Compatibility

• 2001-2003 Toyota Highlander 3.0L

Frequently Asked Questions & Fitment Warnings

Does this fit the XU20 Highlander?

Yes. This fits 2001-2003 Toyota Highlander models with the 1MZ-FE 3.0L V6. Excludes 2.4L 4-cylinder trims; confirm engine size before ordering.

Will this clear P1135 or P0420 codes?

Yes, if sensor-related. New sensors resolve heater circuit faults (P1135/P1155) and false P0420 catalyst codes after an ECU reset.

Is wiring splicing required for installation?

No. Pre-wired OEM connectors install directly; apply anti-seize only to the threads and torque to 30 lb-ft.

The Toyota Precision Standard

Engineered for accurate ECU signal feedback, this matched sensor kit maintains clean closed-loop combustion and CEL-free operation on XU20 platforms. Built to restore emissions compliance and factory throttle response.