Bosch 17251 Oxygen Sensor - Upstream

Overview

Bosch 17251 is a specific-fit wideband oxygen sensor for upstream applications on select BMW models. As part of Bosch’s Actual OE Oxygen Sensor line, it delivers precise air-fuel ratio feedback for modern engine management systems.

Compatible With BMW Alpina B8 Gran Coupe, BMW M850i xDrive, BMW X5, BMW X6, BMW X7, and related applications listed below, this Bosch oxygen sensor is built for accurate mixture control, stable operation, and reliable emissions monitoring.

Key Features

• Wideband A/F sensor provides continuous air-fuel ratio measurement across the full lambda range.
• Heated design supports faster sensor activity during cold starts and changing load conditions.
• Specific-fit configuration for direct replacement on listed BMW applications.
• Metal housing and robust ceramic construction support durability in high-heat environments.
• 18 mm thread size, 22 mm hex, and 5-wire layout for application-specific installation.

Detailed Description

Bosch 17251 is engineered as an upstream wideband oxygen sensor for select BMW performance and luxury models, including the Alpina B8 Gran Coupe, M850i xDrive, X5, X6, and X7. It uses a planar pump-cell design to provide the ECU with detailed air-fuel data, helping the system maintain precise mixture control under varying driving conditions. Bosch’s OE development background and wideband sensor expertise make this part a strong match for vehicles that rely on accurate feedback for fuel delivery and emissions management.

This part cross-references BMW OE numbers 11787935100 and 11787935130 for the same application. Bosch 17251 is a threaded, heated, wide-band sensor with an oblong male connector and blade terminals, built for the upstream position on the listed vehicles. The Bosch 17251 designation is useful when verifying the correct sensor for service work on BMW applications that require an Actual OE Oxygen Sensor.

What It Helps Address

• Incorrect air-fuel ratio readings from a worn upstream sensor.
• Rough running caused by delayed or inaccurate oxygen feedback.
• Reduced fuel economy from poor mixture control.
• Emissions faults related to sensor response or signal quality.
• Driveability issues during rapid throttle or load changes.

Installation Notes and Tips

Confirm the upstream position, connector style, wire count, and thread size before installation. Bosch 17251 uses a threaded mounting type with an 18 mm thread diameter, 6 terminals, and a 33-inch wiring harness length. Verify the vehicle’s original sensor configuration against the part number 17251 and the listed fitment before replacement.

Quality Assurance

Bosch has more than five decades of OE development experience and supplies oxygen sensors built to OE-proven standards. The Actual OE Oxygen Sensor line reflects Bosch’s focus on precise measurement, fast light-off, and dependable operation in demanding thermal conditions.