Oxygen sensors constantly monitor engine emissions and relays this data to the DME. Using these readings the computer determines the proper air/fuel mixture as well as how efficiently the catalyst system is functioning. Symptoms of a failed oxygen sensor range from an EML to poor fuel economy and severe loss of power. A failed upstream sensor will typically cause the engine to run poorly and a failed downstream sensor will typically present as a catalyst efficiency code.
Sluggish oxygen sensors do a lot more than just light up your dashboard with an annoying Check Engine Light—they directly choke your BMW’s performance.
