Bosch 18117 Oxygen Sensor - Downstream

Bosch Oxygen Sensor for Mazda CX-7

Bosch 18117 is a direct-fit, heated narrow-band oxygen sensor for downstream use on select 2007-2012 Mazda CX-7 models. It provides the ECU with air-fuel-ratio feedback needed for stable closed-loop fuel control and emissions monitoring.

Built as part of the Bosch Engineered Oxygen Sensor line, this replacement sensor reflects Bosch’s OE development experience and uses a ceramic sensing element, controlled heater operation, and high-temperature materials for consistent signal output under demanding exhaust conditions.

Key Features

• Direct-fit oxygen sensor for downstream placement
• Fits 2007-2012 Mazda CX-7, downstream
• Heated narrow-band design for faster closed-loop response
• 4-wire configuration with square female connector
• Threaded mounting with 18 mm thread size and 22 mm hex
• Wiring harness included for application-specific installation
• Standard replacement grade for emission control service
• Bosch part number 18117

Detailed Description

Bosch 18117 is engineered for vehicles that rely on a switching-type oxygen sensor to monitor exhaust oxygen content after the catalyst. On the Mazda CX-7, downstream sensor feedback helps the engine control module verify mixture control and catalyst efficiency while maintaining smooth combustion management. The Bosch Engineered Oxygen Sensor line is based on Bosch’s long OE development history, including narrow-band planar sensor designs that improve light-off speed and closed-loop operation compared with earlier sensor generations.

This Bosch oxygen sensor uses a metal housing, threaded mount, and 4-wire heated layout with a square connector and blade terminals. The direct-fit design supports a clean replacement on the specified Mazda CX-7 applications without requiring universal sensor adaptation. Bosch 18117 is also referenced by part number 18117 in catalog searches for Mazda CX-7 downstream oxygen sensor replacement.

This part cross-references Monroe Shocks & Struts (e.g., L33M18861E9U) for the same application.

What This Sensor Helps Address

• Check engine light related to downstream oxygen sensor performance
• Incorrect air-fuel feedback affecting fuel trim control
• Slow sensor response during closed-loop operation
• Emissions test failures tied to oxygen sensor faults
• Rough or inconsistent combustion control caused by aging sensor output

Installation Notes and Tips

Fits 2007-2012 Mazda CX-7, downstream. Confirm the connector shape, wire count, and threaded sensor location before installation. Use the correct oxygen sensor socket for the 18 mm hex and inspect the exhaust bung threads for damage or corrosion before threading in the new sensor. Bosch 18117 includes the wiring harness for the specified application, and the direct-fit layout is intended to match the original sensor connection point.

Quality Assurance

Bosch backs this oxygen sensor with OE-driven engineering and materials selected for heat and vibration resistance in exhaust service. Bosch 18117 is built to the same standard replacement expectations used across the Bosch Engineered Oxygen Sensor line.