Possible causes – HO2S11 and HO2S21 sensors harness is open or shorted– HO2S11 and HO2S21 sensors circuit connectors (wrong connection)– Faulty Engine Control Module (ECM) Symptoms – Engine Light ON (or Service Engine Soon Warning Light) P0040 BMW OBD Code Description The heated oxygen sensor (HO2S) monitor determines if the HO2S signal response for a…