Bosch 18026 Oxygen Sensor - Downstream

Bosch Validated Oxygen Sensor for Audi

Bosch Validated Oxygen Sensor Part Number 18026 is a specific-fit, downstream narrow-band heated O2 sensor built for precise air-fuel-ratio feedback to the ECU. It supports stable combustion control and emissions management for select Audi applications, including Audi Q5, Audi S5, Audi SQ5, Audi S4, Audi A5 Quattro, and Audi A4 Quattro.

Key Features

• Specific-fit downstream oxygen sensor for select Audi models
• Narrow-band heated sensor design for faster closed-loop operation
• 4-wire configuration with blade terminals and oblong connector
• 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 Validated Oxygen Sensor line backed by Bosch OE development experience

Product Details

Bosch Part Number 18026 uses a narrow-band heated sensing element to deliver accurate oxygen-content feedback after the catalytic converter. Bosch developed this sensor line from decades of OE oxygen sensor engineering, including ceramic sensing elements, optimized heater control, and materials selected for thermal and vibration resistance. The result is a replacement sensor that supports consistent ECU control in demanding driving conditions. This part cross-references Bosch Validated Oxygen Sensor applications using OE-style replacement part number 06E906265Q.

Vehicle Fitment

• Fits 2009-2017 Audi Q5, downstream
• Fits 2015-2017 Audi S5, downstream
• Fits 2010-2013 Audi S5, downstream
• Fits 2014-2017 Audi SQ5, downstream
• Fits 2015-2016 Audi S4, downstream
• Fits 2010-2013 Audi S4, downstream
• Fits 2008-2010 Audi A5 Quattro, downstream
• Fits 2009 Audi A4 Quattro, downstream

What This Sensor Helps Address

• Incorrect downstream oxygen sensor readings
• Check engine light conditions related to O2 sensor performance
• Delayed closed-loop fuel control after sensor aging
• Emissions test failures tied to sensor response issues
• Rough combustion control caused by degraded sensor output

Installation Notes

Install this sensor in the downstream position only for the listed Audi applications. Verify the 18 mm thread size, 22 mm hex, 4-wire connector layout, and oblong plug shape before installation. Because this is a threaded sensor with a specific-fit harness, compare the original connector and routing to the vehicle’s existing sensor location before replacement. For Audi Q5, Audi S5, Audi SQ5, Audi S4, Audi A5 Quattro, and Audi A4 Quattro applications, confirm the downstream placement matches the original part.

Quality Assurance

Bosch Validated Oxygen Sensor Part Number 18026 is built on Bosch OE development experience and validated replacement engineering for consistent sensor performance. Bosch has supplied oxygen sensor technology to vehicle manufacturers for more than five decades, and this product line reflects that OE-focused design approach.