Delphi ES20390 Oxygen Sensor - Rear

Rear Oxygen Sensor for Mazda 3

Delphi ES20390 is a heated rear oxygen sensor built for direct-fit replacement on select Mazda 3 applications. It uses a 4-wire design, a square connector, and an 18 x 1.5 mm thread size to match the original sensor interface on covered vehicles.

Compatible With 2006-2009 Mazda 3, rear, without California Emission System. Delphi draws on OE heritage and supplier experience to build aftermarket parts with the same application knowledge used in original equipment development.

Key Features

• Heated oxygen sensor for rear exhaust monitoring
• 4-wire configuration for the listed application
• Square connector shape for OE-style connection
• 18 x 1.5 mm thread size
• 800.0 overall length
• Package contents: oxygen sensor and instruction sheet
• Delphi part number ES20390

Detailed Description

This Delphi oxygen sensor is specified for the rear position on 2006-2009 Mazda 3 models without California Emission System. It is used to monitor exhaust oxygen content after the catalytic converter, helping the engine control system evaluate catalyst performance and maintain proper fuel control strategy. If you are replacing a worn rear sensor on a Mazda 3, ES20390 provides the correct connector style, thread size, and heated sensor layout for the listed fitment.

This part cross-references DENSO Auto Parts 234-4392 for the same application.

What It Helps Address

• Check engine light related to rear oxygen sensor performance
• Fault codes tied to slow sensor response or heater circuit issues
• Incorrect exhaust feedback readings from a degraded sensor
• Emissions test failures caused by a failing rear sensor
• Rough fuel control behavior linked to inaccurate oxygen data

Installation Notes and Tips

Verify the vehicle is a 2006-2009 Mazda 3 with rear sensor placement and without California Emission System before ordering. Match the square connector, 4-wire layout, and 18 x 1.5 mm thread size to the original part. Inspect the harness routing and exhaust bung condition during replacement, and follow the included instruction sheet for installation steps.

Quality Assurance

Delphi builds this replacement sensor with OE experience and application knowledge developed through long-term supplier work with major automakers. That OE background is reflected in the ES20390 design and fitment-specific construction for the listed Mazda 3 applications.