On a 1999 Ford Explorer 4.0L SOHC engine, the Bank 2 Sensor 1 (O2S Bank 2 Sensor 1) oxygen sensor is located on the exhaust manifold
after the catalytic converter on the passenger side (right side) of the engine. Bank 2 always refers to the passenger side bank of cylinders in this engine configuration. Sensor 1 refers to the sensor before the catalytic converter (on bank 1), whereas sensor 2 is after.
Keep in mind that this is a general location. The exact placement might vary slightly depending on specific vehicle modifications or manufacturing tolerances. It's best to consult a repair manual specific to your 1999 Ford Explorer 4.0L SOHC or use a visual guide (like an online parts diagram) that shows the sensor's precise location on your model year.
