DENSO Oxygen / Lambda Sensor – Post Cat / Downstream • DOX-0334

Suitable for Mazda MX-5 Mk3 / Mk3.5 / Mk3.75 (NC) 1.8 and 2.0 petrol models. This is the downstream / post-catalyst diagnostic oxygen sensor.

DENSO DOX-0334 is a Direct Fit heated oxygen / lambda sensor designed for the rear sensor position on the Mazda MX-5 NC exhaust system. It is supplied with the correct vehicle connector and wiring arrangement, avoiding the need to splice a universal sensor into the original wiring loom.

Unlike the upstream regulating sensor, the downstream sensor is located after the catalytic converter and is primarily used by the engine-management system to monitor exhaust oxygen levels after the catalyst and assess catalytic-converter operation.

Product Specifications

• Brand: DENSO
• Product range: Direct Fit
• Product type: Oxygen / lambda sensor
• Sensor function: Diagnostic sensor
• Installation position: Downstream / post-catalyst / rear
• Sensor type: Switching-type oxygen sensor
• Element type: Finger / thimble-type sensor
• Heating function: Heated
• DENSO part number: DOX-0334
• DENSO cross-reference: 234-4340
• DENSO reference: 234000-4853
• Thread size: M18 x 1.5
• Cable length: 440 mm
• Number of wires: 4
• Number of pins: 4
• Connector: Direct-fit vehicle connector
• Thread: Pre-greased
• Net weight: Approx. 102 g
• GTIN / EAN: 8717613016558
• Mazda OE references: LFG2-18-861A / LFG2-18-861B
• Quantity required per vehicle at this position: 1
• Quantity supplied: 1 sensor

Important Sensor Position

DOX-0334 is the downstream / post-catalyst diagnostic sensor. It must not be confused with the upstream / pre-catalyst regulating sensor, as the two positions use different sensor specifications and perform different functions.

This DENSO sensor is listed for both 1.8 and 2.0 MX-5 NC applications across the Mk3, Mk3.5 and Mk3.75 production period.

Typical Reasons for Replacement

An oxygen sensor may require replacement because of normal sensor deterioration, heater-circuit failure, contamination, damaged wiring or connector problems. A downstream sensor fault may trigger an engine-management warning light or catalyst-monitoring fault code, although the underlying cause should be correctly diagnosed before replacing components.

Fitment Advice

Confirm that the sensor being replaced is the rear / downstream sensor after the catalytic converter before removal. Compare the electrical connector, cable length and OE reference with the existing component where necessary.

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

• Upstream / pre-catalyst oxygen sensor if separately required
• Catalytic converter condition
• Exhaust gaskets and fasteners
• Exhaust-system leaks where diagnostic faults are being investigated

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 can become difficult to remove after prolonged exposure to heat and corrosion. Correct identification of the rear sensor 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-0334 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.