Bosch 17203 Oxygen Sensor - Upstream

Bosch Wideband O2 Sensor for Mercedes-Benz

Bosch 17203 is an Actual OE Oxygen Sensor built as a specific-fit wideband air-fuel sensor for precise upstream mixture monitoring. It is engineered for 2012-2015 Mercedes-Benz C250 and 2012-2015 Mercedes-Benz SLK250 applications, where accurate air-fuel ratio feedback is critical for drivability, emissions control, and fuel management.

The Bosch Actual OE Oxygen Sensor line focuses on OE-level fit and signal accuracy. This wideband design uses a heated sensor element, a 5-wire harness, and a threaded 18 mm mounting interface with a 22 mm hex size. The oblong male connector, 53.3-inch overall length, and included wiring harness support direct replacement on the specified Mercedes-Benz upstream location.

Key Features

• Part number 17203 Bosch wideband A/F oxygen sensor
• Specific fit for upstream placement on select Mercedes-Benz models
• Heated sensor for faster operating temperature
• Wide-band sensor type for detailed air-fuel ratio measurement
• 5-wire design with included wiring harness
• Threaded 18 mm mounting with 22 mm hex size
• Metal housing with steel finish

Detailed Description

Bosch 17203 is a wideband oxygen sensor that provides continuous air-fuel ratio feedback across the lambda range, giving the engine control unit more precise data than a traditional switching sensor. That level of signal detail supports accurate fuel control during idle, cruise, acceleration, and load changes. For Mercedes-Benz C250 and Mercedes-Benz SLK250 upstream service, this Bosch Actual OE Oxygen Sensor is built to match the original application requirements with a specific-fit connector, threaded mounting, and OE-style sensor architecture.

Bosch developed the planar pump-cell wideband design used in modern engine management systems, and this sensor reflects that OE-focused engineering approach. If you are replacing a failing upstream sensor on a 2012-2015 Mercedes-Benz C250 or 2012-2015 Mercedes-Benz SLK250, Bosch 17203 provides the correct fitment and sensor type for the listed application. This part cross-references Mercedes-Benz 0065422718 for the same application.

What This Sensor Helps Address

• Check engine light related to upstream oxygen sensor performance
• Incorrect air-fuel ratio readings reported to the ECU
• Rough idle or inconsistent throttle response tied to sensor feedback
• Reduced fuel economy caused by inaccurate mixture control
• Emissions test failures linked to oxygen sensor faults

Installation Notes and Tips

Confirm the vehicle is a 2012-2015 Mercedes-Benz C250 or 2012-2015 Mercedes-Benz SLK250 with upstream sensor placement before ordering Bosch 17203. Match the connector shape, wire count, and threaded 18 mm sensor interface to the original part. Inspect the exhaust bung threads and wiring routing before installation, and verify the harness reaches the factory connection point without strain.

Quality Assurance

Bosch backs this Actual OE Oxygen Sensor line with more than five decades of OE development and aftermarket supply experience. The sensor is built with robust ceramic construction and OE-proven design principles used in modern emissions and engine management systems.