Bosch 15501 Oxygen Sensor - Upstream

Bosch Wideband Oxygen Sensor for Subaru

Bosch Validated Oxygen Sensor 15501 is a specific-fit wideband A/F oxygen sensor built for precise air-fuel ratio feedback to the ECU. It is listed for select Subaru upstream applications, including Subaru Baja, Impreza, Legacy, Outback, and Forester models.

Key Features

• Wideband A/F oxygen sensor for continuous, high-precision lambda measurement
• Specific-fit design with 4-wire configuration and included wiring harness
• Heated sensor with optimized heater control for faster operating response
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• Rectangle female connector with blade terminals
• Metal housing and robust ceramic construction for demanding thermal cycles
• Overall length: 23.2 in; sealing surface to connector end: 22 in

Product Details

Bosch 15501 is part of the Bosch Validated Oxygen Sensor line, a product line focused on OE-style replacement sensors with application-specific fitment. This wideband sensor provides the ECU with more detailed air-fuel ratio data than a traditional switching sensor, helping maintain accurate mixture control across changing load and temperature conditions. Bosch’s wideband sensor design uses the planar pump-cell architecture that helped establish the modern standard for engine management and low-emission systems.

This part cross-references Subaru 22641AA280 for the same application. It is a direct-fit option for Subaru upstream oxygen sensor service on 2003 Subaru Forester, 2003-2004 Subaru Impreza, 2003-2004 Subaru Legacy, 2003-2004 Subaru Outback, and 2003-2006 Subaru Baja. Bosch 15501 is also a relevant search match for Subaru Forester upstream oxygen sensor replacement and Subaru Impreza upstream wideband A/F sensor replacement.

Common Issues This Sensor Can Address

• Fault codes related to air-fuel ratio sensor performance
• Unstable fuel mixture control at idle or under load
• Reduced fuel economy caused by inaccurate oxygen sensor feedback
• Rough engine operation tied to delayed or incorrect sensor response
• Emissions concerns from a worn upstream wideband sensor

Installation Notes

Install in the upstream position only for the listed Subaru applications. Verify the 18 mm thread size, 4-wire layout, rectangle female connector, and 19.8 in wiring harness length before installation. Because this is a threaded sensor, use the correct oxygen sensor socket or 22 mm hex tool and follow the vehicle service procedure for connector routing and exhaust-thread preparation.

Quality Assurance

Bosch backs this sensor with more than five decades of OE development in oxygen sensing and engine management technology. The Bosch Validated Oxygen Sensor line is built to OE-proven standards for accurate signal output, reliable heater performance, and durable operation in high-temperature exhaust environments.