Bosch 15431 Oxygen Sensor - Upstream Rear

Bosch Validated Oxygen Sensor for Mazda 6

Bosch 15431 is a narrow-band heated oxygen sensor built for precise air-fuel ratio feedback to the ECU. It supports stable combustion control and emissions management for 2003-2008 Mazda 6 applications with upstream rear placement.

As part of the Bosch Validated Oxygen Sensor line, this sensor reflects Bosch’s OE development history in oxygen sensing, including faster sensor response, accurate lambda measurement, and durable construction for demanding exhaust conditions.

Key Features

• Specific-fit oxygen sensor for 2003-2008 Mazda 6, upstream rear
• Narrow-band heated design for closed-loop fuel control
• 4-wire configuration with rectangular male connector
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• Metal housing and high-temperature-resistant construction
• Wiring harness included for direct replacement service
• Bosch part number 15431 for catalog and cross-reference use

Detailed Description

Bosch 15431 is a standard replacement oxygen sensor engineered for precise exhaust feedback in the Mazda 6. It uses a heated narrow-band sensing element to help the engine control module maintain the correct air-fuel mixture during warm-up and normal driving, supporting smoother operation and emissions control. The 6.6-inch wiring harness, 4 blade terminals, and threaded 18 mm mounting format match the specified application for straightforward service replacement. Bosch part number 15431 is also listed as a direct reference for this application.

This Bosch Validated Oxygen Sensor line is backed by Bosch’s long OE development background in oxygen sensing technology. Bosch began with early thimble-style sensors and later advanced to planar narrowband designs that improve response time and closed-loop operation. For Mazda 6 owners searching for a 2003-2008 Mazda 6 upstream rear oxygen sensor, Bosch 15431 provides the correct fitment details and OE-style construction.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air-fuel ratio feedback to the ECU
• Slow sensor response during closed-loop operation
• Rough idle or drivability issues tied to exhaust feedback faults
• Emissions test failures caused by a worn upstream rear sensor

Installation Notes and Tips

Confirm the upstream rear position and connector style before installation on the Mazda 6. Match the 18 mm thread size, 22 mm hex, and 4-wire rectangular connector to the original sensor. Inspect the harness routing and exhaust threads before installation, and verify the connector locks securely after replacement.

Quality Assurance

Bosch oxygen sensors are developed from decades of OE sensor engineering and validated for aftermarket use with OE-proven design principles. This part cross-references Monroe Shocks & Struts (e.g., AJ5818861B) for the same application.