Denso 234-4721 Oxygen Sensor - Upstream

Denso OE Style Oxygen Sensor 234-4721

Denso 234-4721 is an OE-style heated oxygen sensor built for exact replacement and first-time fit. It is engineered for specific applications on the Mazda Protege and Mazda Protege5, with a threaded mounting design and a 4-wire female connector for direct installation.

For drivers searching for a Mazda Protege upstream oxygen sensor or a Mazda Protege5 upstream O2 sensor, this Denso part number 234-4721 matches the original-style configuration and wiring layout used in the listed applications.

Key Features

• OE Style replacement oxygen sensor for specific fit applications
• Heated sensor design for faster operating response
• 4-wire configuration with female connector
• Threaded mounting type with 0.708 in. thread diameter
• 9.45 in. wiring harness length for proper routing
• Built to OE standards for accurate replacement fitment
• Aluminum oxide trap layer helps protect the ceramic element from silicone and lead contamination

Product Details

Denso 234-4721 is part of Denso’s OE Style line, which focuses on direct-fit replacement sensors built to match original equipment dimensions and electrical requirements. This oxygen sensor is designed for upstream placement on 2001-2003 Mazda Protege and 2002-2003 Mazda Protege5 models. The specific-fit design helps simplify replacement on vehicles that require the correct connector, thread size, and harness length.

This part cross-references Bosch 13870 and NTK 22533 for the same application.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air-fuel mixture readings
• Reduced fuel economy caused by a worn upstream sensor
• Slow sensor response during closed-loop operation
• Driveability issues tied to contaminated or aging O2 sensor elements

Installation Notes

Verify the upstream sensor location before ordering and confirm connector style, thread diameter, and harness length against the original part. This sensor uses a threaded mounting design and a female connector, so the vehicle-side connector and exhaust bung must match the listed specifications. For best results, inspect the harness routing and connector condition before installation.

Compatible With 2001-2003 Mazda Protege, upstream, and 2002-2003 Mazda Protege5, upstream.

Quality Assurance

Denso manufactures and tests this oxygen sensor to OE standards for consistent fit and performance. The OE Style product line is built around direct replacement accuracy, helping ensure the right part and the right fit for the listed Mazda applications.