Bosch 13574 Oxygen Sensor - Downstream Left, Downstream Right or Upstream Left

Bosch Validated Oxygen Sensor for Mazda

Bosch Validated Oxygen Sensor Part Number 13574 is a specific-fit, narrow-band heated O2 sensor built for precise air-fuel-ratio feedback to the ECU. It supports stable combustion control and emissions management across changing engine conditions, making it a direct replacement for select Mazda 626 and Mazda Millenia applications.

The Bosch Validated Oxygen Sensor line draws on Bosch OE development in oxygen sensing, including narrowband designs that improve response time and closed-loop operation. This sensor uses a threaded metal housing, a rectangular female connector, and a 4-wire harness for a factory-style electrical connection.

Key Features

• Part Number 13574 Bosch Validated Oxygen Sensor
• Narrow-band heated oxygen sensor for air-fuel-ratio feedback
• Specific fit replacement with included wiring harness
• 4-wire design with pin terminals and rectangular female connector
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• Metal housing for durability in high-heat exhaust locations
• Wiring harness length: 21.4 in; overall length: 24.8 in

Fitment

• Fits 2001-2002 Mazda 626, upstream left.
• Fits 1995-2002 Mazda Millenia, downstream left.
• Fits 2000 Mazda 626, upstream left, without California Emission System; alternative fit 1.
• Fits 2000 Mazda 626, upstream left, with California Emission System; exact fit.
• Fits 1998-1999 Mazda 626, upstream left; alternative fit 1.
• Fits 1995-1996 Mazda Millenia, downstream right; exact fit.

What This Sensor Helps Address

• Incorrect oxygen sensor signal to the ECU
• Rough idle caused by inaccurate air-fuel feedback
• Delayed closed-loop fuel control after startup
• Elevated emissions from a worn or slow-responding sensor
• Check engine light concerns related to O2 sensor performance

Installation Notes

Confirm the sensor position before ordering, since this part is listed for upstream left, downstream left, and downstream right applications depending on vehicle and emissions setup. Match the 4-wire connector, threaded mount, 18 mm thread size, and harness length to the original sensor before installation. For 2000 Mazda 626 applications, verify whether the vehicle has California Emission System equipment, as fitment differs by configuration.

Quality Assurance

Bosch has decades of OE oxygen sensor development behind this Validated Oxygen Sensor line, with designs focused on accurate lambda measurement, fast light-off, and reliable heater control under thermal and vibration load. This part cross-references KJ0318861B9U and KL4718861B for the same application.