The BMW E39 was the basis of the 5 series. It was manufactured in 1995 and introduced to the United States in 1997, running its tenure until 2004 when the BMW E60/E61 succeeded it. Dual manifolds from the engine and two converters presents four oxygen sensors in the E39's exhaust system. The two front sensors monitor the spent fuel to air ratio and the two rear sensors monitor the emissions post catalytic converter. They transmit the data via voltage signals to the computer in the engine. If there is an anomaly in the data, the computer will trigger the malfunction indicator light and the "check engine" light.
Locate the diagnostic link connector (DLC) for the BMW E39. It is located under the driver's side dashboard near the steering wheel post.
Plug the OBD II code reader into the DLC.
Turn the ignition key to the key on/engine off position. This is two clicks forward in the ignition that empowers the electrical components but does not activate the engine.
Read the menu board of the code reader. Use the scroll buttons on the face of the code reader to maneuver through the menu options. Choose the "Read Codes" selection and press the "Enter" button. This option will take a minute to send the command the computer of the engine. Once it has communicated and discovered the status of the diagnostic trouble code (DTC), it will display the universal code with a brief description on the screen of the code reader.
Compare the information of the code to determine the oxygen sensor or sensors that have failed to the code guide (supplied with the code reader). The brief description on the menu of the code reader (depending on the individual code reader) may even indicate which sensor has failed or detected a problem.
