Where are the positions of BMW's front oxygen sensors 1 and 2?

[VanColin]

The first sensor always refers to the upstream oxygen sensor (before the catalytic converter), and the second sensor always refers to the downstream oxygen sensor (after the catalytic converter). A four-cylinder engine generally has only one bank, so the first sensor in bank 1 refers to the upstream sensor, and the second sensor in bank 1 refers to the downstream sensor. For six-cylinder or eight-cylinder engines: in the case of rear-wheel drive (with the pulley at the front of the car), the passenger side is bank 1, and the driver side is bank 2. The effects of a damaged oxygen sensor are as follows: Abnormal vehicle signals: An oxygen sensor malfunction usually triggers a warning light, causing abnormal signal output. The engine may shake, produce a sputtering exhaust sound, emit a pungent odor, and even disrupt the air-fuel ratio, leading to black smoke emission. If the front oxygen sensor is damaged, it must be replaced immediately and should no longer be used. Abnormal vehicle operation: If the oxygen sensor or its connecting circuit fails, it not only increases emissions beyond the standard but also worsens the engine's operating conditions. This can lead to symptoms such as stalling at idle, inaccurate engine operation, reduced power, and an imbalanced engine air-fuel mixture, resulting in increased fuel consumption.