Bosch 15814 Oxygen Sensor - Downstream

Bosch Actual OE Oxygen Sensor 15814

Bosch 15814 is a narrow-band heated oxygen sensor built for downstream monitoring on select Subaru applications. It provides precise air-fuel-ratio feedback to the ECU, helping maintain stable combustion control and lower emissions under changing operating conditions.

Compatible with Subaru Baja, Legacy, and Outback downstream applications, this Bosch Actual OE Oxygen Sensor uses a threaded mounting design, a square female connector, and a 4-wire harness for direct-fit replacement. The Bosch 15814 is a practical choice when you need OE-style signal response and reliable closed-loop operation.

Key Features

• Actual OE Oxygen Sensor from Bosch
• Narrow-band heated oxygen sensor design
• Specific fit replacement with threaded mounting
• 4-wire configuration with included wiring harness
• Square female connector with pin terminals
• 18 mm thread size and 22 mm hex size
• Downstream sensor application for select Subaru models

Product Details

Bosch developed its oxygen sensor technology over decades of OE engineering, starting with early sensor designs and later advancing to planar narrowband construction for faster light-off and quicker closed-loop response. The Bosch 15814 continues that OE-focused approach with a ceramic sensing element, controlled heater operation, and materials selected for high-temperature and vibration resistance. This makes it a strong fit for drivers servicing a 2003-2006 Subaru Baja downstream oxygen sensor location, a 1999-2004 Subaru Legacy downstream oxygen sensor location, or a 2000-2004 Subaru Outback downstream oxygen sensor location. This part cross-references Subaru 22690AA73A for the same application.

What It Helps Address

• Check engine light related to downstream oxygen sensor performance
• Incorrect air-fuel feedback to the ECU
• Slow sensor response during closed-loop operation
• Emissions test failures tied to sensor degradation
• Rough combustion control caused by aging O2 sensor output

Installation Notes

Verify the downstream position, connector shape, wire count, and thread size before installation. This Bosch oxygen sensor uses a threaded mount with an 18 mm thread diameter and a 22 mm hex, so proper removal tools help prevent damage during service. Confirm harness routing and connector orientation on the Subaru Baja, Legacy, or Outback before final connection.

Quality Assurance

Bosch supplies OE-proven oxygen sensor technology to the aftermarket, drawing on more than five decades of development in air-fuel sensing and emissions control. The Bosch 15814 is built to deliver consistent signal accuracy and durable operation in demanding thermal and vibration conditions.