Bosch 15521 Oxygen Sensor

Bosch Validated Oxygen Sensor for Nissan and INFINITI

Bosch Validated Oxygen Sensor 15521 is a specific-fit, narrow-band heated O2 sensor built for downstream applications on select Nissan and INFINITI vehicles. It uses a threaded 18 mm mount, 22 mm hex size, and a 4-wire square connector to deliver accurate air-fuel-ratio feedback to the ECU for stable closed-loop control.

Compatible With 2002-2009 Nissan Quest, Maxima, and Altima, plus 2002-2006 INFINITI Q45 and 2003-2004 INFINITI M45, this Bosch oxygen sensor supports precise emissions monitoring in downstream positions. The Bosch Validated Oxygen Sensor line reflects Bosch’s OE development background and focus on durable, heater-equipped sensor construction for demanding exhaust conditions.

Key Features

• Bosch Validated Oxygen Sensor 15521 for specific-fit replacement applications
• Narrow-band heated oxygen sensor with 4-wire configuration
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• Square male connector with blade terminals
• Steel finish and metal housing for exhaust-system durability
• Wiring harness included
• Designed for downstream sensor locations on select Nissan and INFINITI models

Detailed Description

Bosch 15521 is a standard replacement oxygen sensor engineered for downstream monitoring on select Nissan Quest, Maxima, Altima, Q45, and M45 applications. As a narrow-band heated sensor, it helps the ECU read exhaust oxygen content accurately so the engine can maintain proper fuel control after the catalytic converter. Bosch’s long OE development history is reflected in the sensor’s ceramic element design, heater control strategy, and high-temperature materials chosen for consistent operation under heat and vibration.

This part cross-references 226A0AR210 for the same application.

What This Sensor Helps Address

• Check engine light related to downstream oxygen sensor performance
• Incorrect air-fuel feedback after the catalytic converter
• Slow sensor response during closed-loop operation
• Emissions test failures tied to oxygen sensor faults
• Rough or unstable fuel control caused by a worn O2 sensor

Installation Notes and Tips

Install Bosch Validated Oxygen Sensor 15521 in the confirmed downstream position for the listed Nissan and INFINITI applications. Verify connector shape, terminal count, thread size, and harness routing before installation. Use the correct oxygen sensor socket for the 22 mm hex and apply proper exhaust-thread service practices to avoid damage during removal and installation.

Quality Assurance

Bosch draws on more than five decades of OE oxygen sensor development, and this Validated Oxygen Sensor line is built to meet the demands of modern emissions systems with accurate signal output and durable construction.