Delphi ES20120 Oxygen Sensor - Rear

Rear Oxygen Sensor for Mazda Protege

Delphi ES20120 is a heated rear oxygen sensor built for 1999-2001 Mazda Protege applications. It uses a 4-wire design, a square connector, and an 18 x 1.5 mm thread size for direct replacement service on the rear position.

Built from Delphi’s OE experience and aftermarket engineering knowledge, this oxygen sensor is made for accurate exhaust feedback on the Mazda Protege rear oxygen sensor application. The ES20120 also cross-references DENSO Auto Parts 234-4751 for the same application.

Key Features

• Heated oxygen sensor for rear exhaust monitoring
• 4-wire configuration for proper signal and heater circuit operation
• Square connector shape for application-specific fitment
• 18 x 1.5 mm thread size
• Overall length: 880.0
• Package contents: oxygen sensor and instruction sheet
• Compatible with 1999-2001 Mazda Protege, rear

Detailed Description

The Delphi ES20120 oxygen sensor is engineered for rear-position use on the 1999-2001 Mazda Protege. As a heated sensor, it helps the engine control system monitor exhaust oxygen levels after the catalytic converter, supporting proper fuel control and emissions system operation. Delphi’s OE heritage is reflected in the sensor design, materials, and application-specific fitment.

For buyers searching for a rear oxygen sensor for Mazda Protege 1999-2001 or a Delphi ES20120 replacement, this part provides the correct connector style, thread size, and wire count for the listed application. It is also a direct interchange reference for DENSO Auto Parts 234-4751.

What It Helps Address

• Check engine light related to rear O2 sensor performance
• Faulty oxygen sensor heater circuit codes
• Incorrect exhaust oxygen readings after the catalytic converter
• Emissions test failures tied to sensor response issues
• Rough fuel control caused by inaccurate exhaust feedback

Installation Notes and Tips

Verify rear-position fitment before installation and confirm the connector shape, thread size, and wire count match the original sensor. Inspect the harness routing and exhaust threads before removal, and follow the included instruction sheet during installation. Because this is a rear oxygen sensor for the Mazda Protege, proper placement in the exhaust stream is important for accurate readings.

Quality Assurance

Delphi draws on more than a century of OE experience and supplier knowledge from top automakers, with that engineering background built into its aftermarket parts. The ES20120 is produced to support dependable fitment and consistent sensor performance for the specified Mazda Protege applications.