Bosch 15427 Oxygen Sensor - Upstream or Upstream Right

Bosch Oxygen Sensor for Mazda Applications

Bosch Part Number 15427 is a narrow-band heated oxygen sensor built for specific Mazda applications, including 2003-2005 Mazda 6 upstream and 2001-2002 Mazda Millenia upstream right. It provides the ECU with air-fuel-ratio feedback needed for stable closed-loop fuel control and emissions management.

Key Features

• Specific-fit Bosch Engineered Oxygen Sensor for direct application matching
• Narrow-band heated O2 sensor for faster closed-loop operation
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• 4-wire design with blade terminals and rectangular connector
• Wiring harness included with 22.1 in harness length
• Metal housing with high-temperature-resistant construction
• Bosch Part Number 15427 for OE-style replacement identification

Product Details

Bosch Engineered Oxygen Sensor 15427 uses a switching-type narrow-band design to measure exhaust oxygen content and send accurate feedback to the engine control unit. Bosch developed this sensor line from its long-running OE oxygen sensor engineering, including planar narrowband technology that improves light-off speed and closed-loop response. For Mazda 6 and Mazda Millenia service work, this sensor supports precise fuel trim control under changing load and temperature conditions.

This part cross-references KL1D188619U and L32118861B for the same application. Bosch 15427 is a practical choice when replacing a worn upstream sensor on a Mazda 6 or Mazda Millenia and restoring proper sensor response.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Slow or inaccurate upstream air-fuel ratio feedback
• Rich or lean fuel trim conditions caused by sensor aging
• Reduced closed-loop fuel control response
• Emissions test failures tied to sensor degradation

Installation Notes and Tips

Install Bosch 15427 only in the confirmed upstream positions listed for the vehicle. Verify the 4-wire connector, threaded 18 mm mounting, and harness routing before installation. Because oxygen sensors operate in high-heat exhaust locations, inspect the connector, wiring, and exhaust threads for damage before fitting the new sensor.

Quality Assurance

Bosch backs this oxygen sensor with more than five decades of OE development in emissions and engine management sensing. The design uses ceramic sensing elements, controlled heating, and heat-resistant materials to maintain consistent operation in demanding thermal and vibration conditions.