The oxygen sensor installs in the upstream position on select 2016-2021 BMW applications. It measures the exhaust air-fuel ratio across a broad range so the engine computer can meter fuel precisely. It uses a female oblong connector with 5 terminals.

Walker Products 250-25132 Oxygen Sensor Features:

• Fits 2016-2018 BMW 340i, 340i xDrive; 2016-2020 BMW 740i; 2017-2019 BMW 340i GT xDrive
• Fits 2017-2020 BMW 440i, 440i Gran Coupe, 440i xDrive, 440i xDrive Gran Coupe, 540i, 540i xDrive, 740i xDrive; 2017-2021 BMW M240i, M240i xDrive
• Fits 2018-2019 BMW 640i xDrive Gran Turismo; 2018-2021 BMW X3; 2019-2021 BMW X4 with the 3.0L I6 engine
• Sensor location by application: B1S1 (bank and sensor number)
• 5-wire wide-band oxygen sensor
• Built-in heater for fast warm-up
• M18x1.5 threaded mounting with a 22 mm hex, 375 mm (14.8 in.) overall length
• Female oblong connector at the harness end with 5 spade terminals
• Platinum electrode layer with a protective coating against combustion residue