Delphi ES20121 Oxygen Sensor - Front

Delphi ES20121 Oxygen Sensor for Mazda 626

Delphi ES20121 is a heated front oxygen sensor built for precise exhaust monitoring and OE-style replacement performance. It fits select 2000-2002 Mazda 626 applications, including the 2000 Mazda 626 with California Emission System and 2001-2002 Mazda 626 front positions.

Key Features

• Heated oxygen sensor for faster operating temperature and stable signal output
• 4-wire design with square connector shape
• 18 x 1.5 mm thread size for direct-fit installation
• 320.0 overall length for the specified application
• Includes oxygen sensor and instruction sheet
• OE heritage backed by Delphi’s 100 years of original equipment experience

Detailed Description

Delphi ES20121 is an emission control sensor engineered for front-position use on select Mazda 626 models. As a heated oxygen sensor, it helps the engine control system monitor exhaust oxygen content more quickly after startup, supporting accurate fuel control and emissions management. Delphi draws on long-standing OE supplier experience, and that background is reflected in the fit, connector style, and sensor construction of this replacement part. This part cross-references Bosch 15278 for the same application.

Compatible With: 2000 Mazda 626, front, with California Emission System; 2001-2002 Mazda 626, front. Search terms such as Mazda 626 front oxygen sensor replacement, 2000 Mazda 626 California emissions O2 sensor, and Delphi ES20121 oxygen sensor fitment all point to this application.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air-fuel mixture readings from a worn front sensor
• Slow sensor response during cold starts
• Emissions test failures tied to front O2 sensor faults
• Rough idle or drivability issues caused by inaccurate exhaust feedback

Installation Notes and Tips

Verify the connector shape, wire count, thread size, and front position before installation. Confirm the vehicle is a 2000-2002 Mazda 626 and match the California Emission System note where applicable. Inspect the exhaust bung threads and wiring routing before tightening the sensor to the specified 18 x 1.5 mm thread interface. Use the included instruction sheet during installation.

Quality Assurance

Delphi builds this oxygen sensor using OE heritage and knowledge developed through supplier experience with major automakers. That background supports consistent replacement quality for Mazda 626 front oxygen sensor service and related emission control repairs.