The 4-wire wide-band air/fuel ratio sensor is a replacement sensor for 2015-2024 Subaru Legacy, Outback and 2011-2012 Toyota Sienna in the upstream position. It reports the exhaust air-fuel ratio so the engine computer can meter fuel precisely. A built-in heater brings the element to operating temperature quickly after a cold start.

Walker Products 350-64044 Air/Fuel Ratio Sensor Features:

• Fits 2015-2024 Subaru Legacy, Outback; 2011-2012 Toyota Sienna
• Engine coverage includes 2.5L H4, 2.7L I4, 3.6L H6 applications
• Sensor location by application: B1S1 (bank and sensor number)
• 4-wire wide-band air/fuel ratio sensor
• Built-in heater for fast warm-up
• M18x1.5 threaded mounting with a 22 mm hex, 225 mm (8.9 in.) overall length
• Male square connector at the harness end
• Platinum electrode layer with a protective coating against combustion residue