O2 Oxygen Sensor Upstream Downstream for Mazda CX-9 (2011-2015) 3.7L

Direct-Fit Complete O2 Oxygen Sensor Kit for 2011-2015 Mazda CX-9 (TB)

What it Does: The complete upstream and downstream oxygen sensor kit replaces degraded factory lambda sensors on the 2011-2015 Mazda CX-9 to restore closed-loop air-fuel metering, resolve check engine codes, and optimize fuel economy.

The Stock Mazda CX-9 Sensor Degradation

Over extended thermal cycles, the factory zirconia thimble elements inside the OEM sensors on the MZI 3.7L V6 suffer from silicone poisoning, exhaust carbon contamination, and internal heater circuit failure. As response times lag, the PCM relies on inaccurate voltage feedback, forcing the fuel trims excessively rich or lean. This manifests as catalyst-inefficiency trouble codes (P0420/P0430), slow throttle tip-in, fouled spark plugs, and increased tailpipe emissions.

The Engineering Solution

This four-piece matched sensor kit provides two wideband air-fuel ratio upstream sensors and two switching downstream sensors designed specifically for the TB chassis exhaust geometry. Built with high-grade planar ceramic substrates, fast-acting internal ceramic heaters, and double-laser-welded stainless steel bodies, these units resist thermal shock and mechanical vibration. Factory-pinned pigtails with weather-pack connectors allow direct plug-and-play installation into the OE harness without wire splicing or pin depinning.

What's Included

• 2x Upstream Oxygen Sensors (Bank 1 & Bank 2 Sensor 1)
• 2x Downstream Oxygen Sensors (Bank 1 & Bank 2 Sensor 2)

Technical Specifications

Compatibility

• 2011 Mazda CX-9 3.7L V6 (Sport, Touring, Grand Touring)
• 2012 Mazda CX-9 3.7L V6 (Sport, Touring, Grand Touring)
• 2013 Mazda CX-9 3.7L V6 (Sport, Touring, Grand Touring)
• 2014 Mazda CX-9 3.7L V6 (Sport, Touring, Grand Touring)
• 2015 Mazda CX-9 3.7L V6 (Sport, Touring, Grand Touring)

Frequently Asked Questions & Fitment Warnings

Does this fit the TB CX-9?

Yes, this is a direct fit for the 2011-2015 Mazda CX-9 equipped with the 3.7L MZI V6 engine. Does not fit 2007-2008 CX-9 models equipped with the earlier 3.5L engine or 2016+ second-generation 2.5T SkyActiv-G models.

Do these sensors require anti-seize compound on the threads prior to installation?

Yes, ensure high-temperature anti-seize is applied to the sensor threads while taking strict care not to contaminate the protective perforated sensor tip.

The Mazda Calibration Standard

Preserve factory powertrain drivability, throttle responsiveness, and catalytic converter longevity with precise closed-loop fueling feedback built to endure sustained operating temperatures.