DENSO Oxygen / Lambda Sensor – Pre Cat / Upstream • DOX-0317

Suitable for selected Mazda MX-5 Mk1 / NA 1.6 and 1.8 models from approximately July 1996, plus early MX-5 Mk2 / NB 1.6 and 1.8 models up to approximately August 2000 production. This is the upstream / pre-catalyst regulating oxygen sensor.

DENSO DOX-0317 is a Direct Fit heated oxygen / lambda sensor supplied with the correct vehicle-specific connector and wiring arrangement. It is designed as a direct replacement for the corresponding original sensor without requiring a universal sensor to be spliced into the vehicle wiring loom.

This sensor is positioned before the catalytic converter and operates as a regulating sensor. It measures oxygen content in the exhaust gases and provides feedback to the engine-management system so that the ECU can control the air-fuel mixture.

Product Specifications

• Brand: DENSO
• Product range: Direct Fit
• Product type: Oxygen / lambda sensor
• Sensor type: Switching-type oxygen sensor
• Sensor design: Heated, finger-type sensor
• Sensor function: Regulating sensor
• Installation position: Upstream / pre-catalyst
• DENSO part number: DOX-0317
• DENSO reference: 234000-4070
• DENSO reference: 065500-4820
• Thread size: M18 x 1.5
• Cable length: 880 mm
• Number of pins: 4
• Connector: Direct-fit vehicle connector
• Thread: Pre-greased
• Net weight: Approx. 142 g
• GTIN / EAN: 8717613016381
• Mazda OE references: BP3A-18-861 / BP4W-18-861B
• Quantity required per vehicle at this position: 1
• Quantity supplied: 1 sensor

Important Fitment Note

DOX-0317 is the upstream / pre-catalyst regulating sensor. It should not be assumed suitable for every MX-5 NA or NB simply because the engine capacity is the same.

Detailed application data restricts the later Mk1 / NA applications to approximately July 1996 onward, while early Mk2 / NB applications are generally restricted to vehicles produced up to approximately August 2000. Later NB and Mk2.5 vehicles use different sensor specifications depending on engine and application.

Typical Reasons for Replacement

An oxygen sensor may require replacement because of age-related deterioration, heater-circuit failure, contamination, damaged wiring or connector problems. A faulty regulating sensor can contribute to an engine-management warning light, incorrect mixture control, poor running or increased fuel consumption, although these symptoms can have other causes and should be properly diagnosed before replacing components.

Fitment Advice

Confirm that the sensor being replaced is the upstream / pre-catalyst regulating sensor before removal. Compare the connector, cable arrangement and original Mazda reference where necessary, particularly around model-year change points.

For imported, modified or previously repaired cars, matching the part number or component style on the part being replaced is recommended.

Other Items to Consider

• Downstream / post-catalyst sensor where separately fitted and required
• Exhaust manifold and exhaust gaskets
• Exhaust-system fasteners
• Ignition components where poor running is being investigated
• Routine service components where appropriate

Useful Tools / Consumables

• Suitable oxygen / lambda sensor socket
• Ratchet and extension as required
• Torque wrench
• Penetrating fluid where appropriate for seized exhaust threads

Difficulty Guide

DIY Difficulty: Moderate. The sensor is threaded into the exhaust system and may become difficult to remove after prolonged exposure to heat and corrosion. Correct sensor identification and careful handling of the electrical connector are important.

Why DENSO?

DENSO is a long-established Japanese automotive component manufacturer with extensive experience in engine-management and emissions-control technology. Its Direct Fit lambda sensors are application-specific replacements supplied with the appropriate connector and wiring arrangement for straightforward replacement of the corresponding original component.

What's in the Box?

• 1 x DENSO DOX-0317 Direct Fit oxygen / lambda sensor

Installation Notes

Allow the exhaust system to cool before starting work. Disconnect the electrical connector before removing the existing sensor and avoid twisting or damaging the wiring during installation.

The sensor is supplied with a pre-treated thread. Take care not to contaminate the sensing element and install using the appropriate tightening procedure.