Bosch 13557 Oxygen Sensor - Upstream

Bosch Wideband O2 Sensor for Subaru

Bosch Validated Oxygen Sensor 13557 is a specific-fit wideband air-fuel ratio sensor for select Subaru applications. It delivers continuous, high-precision AFR feedback to the ECU, helping maintain accurate fuel control in real-world driving conditions.

• Wideband A/F oxygen sensor with continuous lambda-range measurement
• Specific fit for direct application matching
• Heated design for faster sensor warm-up
• 4-wire configuration with square male connector and blade terminals
• Threaded mounting with 18 mm thread diameter and 22 mm hex size
• Wiring harness included with 12.7 in harness length
• Metal housing with robust ceramic sensor construction

Bosch Validated Oxygen Sensor Line

The Bosch Validated Oxygen Sensor line focuses on OE-style replacement sensors built around Bosch wideband technology. Bosch introduced the planar pump-cell design that became the standard for modern engine management, and this part reflects that development with fast light-off, controlled heater operation, and stable signal output under changing load and temperature conditions. Part number 13557 is built for Subaru Legacy and Subaru Outback upstream applications, including 2000-2001 Subaru Legacy upstream, 2000-2001 Subaru Outback upstream, and 1999 Subaru Legacy upstream with California Emission System.

This part cross-references 22641AA00A for the same application.

What It Helps Address

• Check engine light caused by a failing upstream air-fuel ratio sensor
• Rough idle or unstable fuel trim readings
• Reduced fuel economy from inaccurate mixture control
• Delayed sensor response during warm-up or load changes
• Emissions test failures related to oxygen sensor performance

Installation Notes

Install Bosch 13557 in the upstream sensor location only for the listed Subaru Legacy and Subaru Outback applications. Verify the 18 mm thread size, 4-wire connector style, and harness routing before installation. Use proper oxygen sensor service tools and follow factory torque specifications to avoid thread or connector damage.

Quality Assurance

Bosch brings more than five decades of OE sensor development to the aftermarket, and this wideband oxygen sensor is built to the same OE-proven standards used in modern engine management systems. For 2000-2001 Subaru Legacy, 2000-2001 Subaru Outback, and 1999 Subaru Legacy California Emission System applications, Bosch 13557 provides a direct replacement solution backed by Bosch engineering experience.