O2 Oxygen Sensor Upstream Downstream for Scion xB (2008-2015) 2.4L

Direct-Fit Upstream & Downstream O2 Oxygen Sensor Kit for 2008-2015 Scion xB (AZE151)

What it Does: This matched upstream and downstream oxygen sensor kit monitors pre- and post-catalyst exhaust oxygen content on the 2008-2015 Scion xB (AZE151) with the 2AZ-FE 2.4L engine to regulate closed-loop fuel trim and verify converter efficiency.

The Stock Scion xB Oxygen Sensor Failure

On the AZE151 Scion xB powered by the 2AZ-FE 2.4L, factory oxygen sensors endure severe thermal cycling, carbon fouling, and oil-ash contamination common to higher-mileage engines. Over time, the internal zirconia ceramic element fractures or slows down, while the integrated heater circuit burns out under continuous electrical load. This causes sluggish millivolt switching and skewed air/fuel ratio feedback, triggering P0138, P0136, P0031, or P2195 fault codes and forcing open-loop rich fueling.

Common Symptoms of a Failing OEM Oxygen Sensor

• Check Engine Light / DTCs: Triggers heater circuit or slow-response codes like P0031, P0136, P0138, or false P0420 catalyst alerts.
• Rich Running & Fouling: Sluggish upstream voltage causes heavy exhaust soot, rough idle, and premature spark plug wear.
• Failed Emissions & Economy Drop: Open-loop ECM fueling reduces fuel mileage and prevents OBD-II emissions readiness monitors from setting.

The Direct-Fit Heated Zirconia Oxygen Sensor Solution

Replacing both sensors as a matched set restores rapid closed-loop ECM communication across the entire exhaust stream of the 2AZ-FE 2.4L. Built with laser-welded stainless steel housings and dual-shielded planar ceramic sensing elements, these direct-fit units resist thermal shock, moisture intrusion, and exhaust-gas poisoning. Factory-length heat-sleeved harnesses and OEM-style weatherproof connectors eliminate wire splicing, ensuring accurate air/fuel telemetry matching OE reference 8946712070.

What's Included

• 1x Upstream Oxygen Sensor (Direct-Fit)
• 1x Downstream Oxygen Sensor (Direct-Fit)

Technical Specifications

Compatibility

• 2008-2015 Scion xB 2.4L (2AZ-FE, 2-Sensor System: 1 Upstream, 1 Downstream)
• Excludes 2004-2006 Scion xA / xB 1.5L (1NZ-FE, different generation and engine)

Frequently Asked Questions & Fitment Warnings

Does this fit the AZE151 xB?

Yes. This is a direct fit for the 2008-2015 Scion xB equipped with the 2AZ-FE 2.4L engine. It does not fit 2004-2006 Scion xA or xB models equipped with the 1.5L engine.

Will this clear P0136, P0138, or P0031 codes without splicing wires?

Yes. Factory-style connectors plug directly into the OEM harness to resolve heater circuit and slow-response faults like P0031, P0136, and P0138 once codes are cleared.

Are both upstream and downstream sensors included for installation?

Yes. This kit includes 1 upstream and 1 downstream oxygen sensor; chase dirty exhaust bung threads if corroded and torque both sensors to factory specification.

The Scion Precision Standard

Engineered for accurate air/fuel stoichiometry, crisp throttle response, and CEL-free emissions readiness on your AZE151. Restore factory closed-loop 2AZ-FE fuel control and reliable daily drivability.