Bosch 15257 Oxygen Sensor - Downstream Front

Bosch Validated Oxygen Sensor for Mazda MPV

This Bosch Validated Oxygen Sensor is a specific-fit, narrow-band heated replacement for the downstream front position on select 2002-2006 Mazda MPV models. Bosch part number 15257 is built to deliver accurate air-fuel-ratio feedback to the ECU for stable combustion control and lower emissions.

As part of the Bosch Validated Oxygen Sensor line, this unit reflects Bosch’s OE development background and focus on direct-fit replacement coverage. Bosch 15257 is engineered for consistent signal response, reliable heater performance, and dependable operation in demanding exhaust temperatures.

Key Features

• Specific-fit oxygen sensor for confirmed Mazda MPV applications
• Fits 2002-2006 Mazda MPV, downstream front
• Narrow-band heated oxygen sensor design
• 4-wire configuration with square connector and blade terminals
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• Wiring harness included for direct replacement use
• Metal housing and high-temperature-resistant construction
• Bosch part number 15257

Detailed Description

Bosch 15257 is a standard replacement oxygen sensor for vehicles that use a narrow-band heated O2 sensor in the downstream front location. It measures exhaust oxygen content and sends the signal to the ECU so the engine can maintain proper air-fuel ratio control during closed-loop operation. For Mazda MPV owners, this sensor provides a direct-fit solution for 2002-2006 models listed in the fitment data.

Bosch developed its oxygen sensor technology from early thimble-style designs to later planar narrowband sensors that improve light-off speed and closed-loop response. This Bosch Validated Oxygen Sensor uses advanced ceramic elements, optimized heater control, and durable materials to maintain stable performance under heat and vibration. If you are searching for a Bosch 15257 oxygen sensor for Mazda MPV downstream front replacement, this part matches the listed application.

This part cross-references Monroe Shocks & Struts (e.g., 172286, 182286) for the same application.

What It Helps Address

• Check engine light related to oxygen sensor performance
• Incorrect air-fuel ratio feedback to the ECU
• Slow closed-loop response after startup
• Rough combustion control caused by a worn O2 sensor
• Emissions test failures tied to sensor degradation

Installation Notes and Tips

Confirm the downstream front position and connector style before installation. This Bosch oxygen sensor uses a threaded mount, 18 mm thread size, 4-wire harness, and square male connector with blade terminals. Inspect the exhaust bung threads and wiring routing before tightening the sensor to specification.

For best results, compare the removed sensor’s connector, harness length, and mounting details against Bosch 15257 before installation. This helps ensure the correct Mazda MPV oxygen sensor replacement for the listed 2002-2006 applications.

Quality Assurance

Bosch has more than five decades of OE oxygen sensor development and supplies aftermarket sensors built to OE-proven standards. Bosch 15257 is part of the Bosch Validated Oxygen Sensor line, backed by Bosch’s long history in emissions control and sensor engineering.