Denso 234-4040 Oxygen Sensor - Downstream Rear

Denso OE Style Oxygen Sensor 234-4040

Denso 234-4040 is a heated, specific-fit oxygen sensor built to OE-style dimensions for direct replacement in select Mazda applications. It is engineered for the downstream rear position on 2000-2005 Mazda 626 and 2003-2005 Mazda 6 models, with the correct connector and threaded mounting for a precise fit.

The Denso OE Style line focuses on exact replacement fitment and sensor performance. This oxygen sensor uses Denso’s aluminum oxide trap layer to help protect the ceramic element from silicone and lead contamination, supporting stable exhaust feedback and consistent engine management.

Key Features

• OE Style replacement oxygen sensor for specific Mazda applications
• Heated sensor design for faster operating response
• Specific fit with a male connector and 4-wire configuration
• Threaded mounting with 0.708 in. thread diameter
• 18.70 in. wiring harness length for application-specific routing
• Built to strict OE standards for replacement accuracy

Detailed Description

This Denso oxygen sensor, part number 234-4040, is designed for downstream rear placement on Mazda 6 and Mazda 626 models listed in the fitment data. It is a direct-fit emission control sensor that helps the engine control system monitor exhaust conditions after the catalytic converter. For buyers searching for a Mazda 6 downstream rear oxygen sensor or a Mazda 626 OE style O2 sensor, this part number provides the correct fitment profile for the listed vehicles.

This part cross-references Bosch 15326 and NTK 22097 for the same application. The Denso OE Style product line is built around first-time fit accuracy and OE-level construction, making it a practical choice when replacing a worn or contaminated sensor on a Mazda 6 or Mazda 626.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Slow or inaccurate exhaust feedback to the engine control module
• Reduced fuel economy caused by a failing downstream sensor
• Emission test failures tied to sensor response issues
• Driveability concerns from contaminated or aging sensor elements

Installation Notes and Tips

Verify the downstream rear position before ordering, since this sensor is specific to the listed applications. Confirm connector style, wire count, and thread size against the original part before installation. Use proper oxygen sensor service tools and follow the vehicle service procedure for removal and torque specifications.

Quality Assurance

Denso manufactures and tests this oxygen sensor to OE standards, with precision-built dimensions intended to match the original application. The aluminum oxide trap layer is included to help protect the sensing element from contamination and support long-term sensor performance.