Original problem was 02 sensor bank 2 sensor, replaced it check engine light turned off then the following Friday I go to get X3 inspected and check engine light comes back on car starts jerkying and shaking I loose power and acceleration changes check engine would turn on ... And then turn off and eventually stayed on IT WASNT BLINKING ! i got to advance Auto had them read the codes and it threw like 22 code all like hex codes don't know that means but examples of some of the codes was ratio,engine time shutdown and basically everything that pointed to O2 sensor issues along with a new problem misfire in cylinder 2 now I have since replaced the ignition coil in cylinder 2 and car went back to normal running smooth no jerkying and check engine light went off so so far I fixed the problem but what did actually happen any answers ???