| decoding the codes of 1999 328iC
So on our 328Ic with a check engine light and resultant code 19 on table 11which indicates an oxygen sensor fault heater circuit cylinders 1-3. This model has a relay where the Bentley maualshows it and its functional. After removing the fuel rail cover and disconnecting the O2 sensor connectors ala the Haynes manual I discovered four wires Red/White/Black/Yellow. Continuity troubleshooting here indicated an open circuit between the red and white on the rearward sensor vs. a continuous circuit on the forward. I believe I have a failed O2 sensor. The confusing part is it would stand to reason the the forward one would be for cylinders 1-3 and the rearward for 4-6. Unless the wiring switches course as it is routed around the engine I am going to have to wait until I can expose the exhaust manifold cover where these sensors are located(someone correct me if I am wrong) to check again. I could just replace them both since this seeminly labor intensive job could take some time. I don't wan to have to do it twice )Any advise apprciated or if I am on the right track hit me back? | 
