First post . My 2001 325i refuses to start - cranks very slow and click, and the headlights come on despite not being turned on and it sounds like the climate control vents are going crazy under the dash. Battery shows 11.8 V when not running. It starts when jumped from another vehicle. Also, the CEL is on and error code P1155 is showing, along with misfire codes on four cylinders. P1155 is "intermittent O2 sensor, bank 2, sensor 2." Leading up to this has been a smell of fuel from the exhaust and a loss of power, along with increased fuel usage. Any ideas what I should check first? I've got the sensor in question but I'm not going to fit it in case that's not the problem! Many thanks, M.