Bosch 15323 Oxygen Sensor - Upstream Left

Bosch Oxygen Sensor for Mazda 626

Bosch Validated Oxygen Sensor 15323 is a specific-fit, narrow-band heated oxygen sensor for precise air-fuel ratio feedback to the ECU. It is listed for the upstream left position on select Mazda 626 models, including 1998-1999 and 2000 applications without the California Emission System.

Key Features

• Specific-fit oxygen sensor for direct application matching
• Narrow-band heated design for closed-loop fuel control
• Round connector with blade terminal and 4-wire harness
• Threaded mounting with 18 mm thread size and 22 mm hex size
• Metal housing with high-temperature-resistant construction
• Wiring harness included for a cleaner replacement setup

Product Details

Bosch 15323 is part of the Bosch Validated Oxygen Sensor line, built around Bosch OE development experience in oxygen sensing technology. The sensor uses a heated narrow-band design to deliver stable signal feedback during warm-up and normal driving, helping the engine control module maintain accurate combustion control. For Mazda 626 owners searching for an upstream left oxygen sensor replacement, Bosch 15323 provides the correct fitment for 1998-1999 Mazda 626 and 2000 Mazda 626 models without the California Emission System.

This part cross-references KLG418861A for the same application.

What This Sensor Helps Address

• Check engine light related to oxygen sensor performance
• Rough idle caused by inaccurate air-fuel ratio feedback
• Reduced fuel control from a slow or aging upstream sensor
• Emissions test failures tied to faulty sensor readings
• Delayed closed-loop operation after cold start

Installation Notes

Install in the upstream left location only when the vehicle match is confirmed. Verify the 18 mm thread size, threaded mounting style, and round connector before installation. Because this is a heated narrow-band sensor, proper connector routing and secure harness placement help protect the wiring from exhaust heat and vibration. Always confirm emission system configuration on 2000 Mazda 626 models, since this listing excludes California Emission System applications.

Quality Assurance

Bosch has more than five decades of OE oxygen sensor development behind this Validated Oxygen Sensor line. The design uses advanced ceramic elements, optimized heater control, and heat-resistant materials to support consistent signal output under demanding thermal and vibration conditions.