Where is the O2 sensor located on your 98 BMW 528i?

On a 1998 BMW 528i, the O2 (oxygen) sensors are located in two places: one is upstream (pre-catalytic converter) and the other is downstream (post-catalytic converter). The upstream sensor is typically found in the exhaust manifold or just before the catalytic converter, while the downstream sensor is located after the catalytic converter in the exhaust system. To access them, you may need to lift the vehicle and work from underneath or remove some engine covers. Always ensure the engine is cool before attempting any maintenance.