This bulletin applies to 2016 BMW 3 Series Gran Turismo vehicles. The Service Engine Soon light (MIL) may be on with only DTC 118602 (oxygen sensor before catalytic converter, fine mixture control, exhaust gas after catalytic converter too lean) stored. The cause: an actual engine related problem and/or DME software issue. Perform the following test plan as recommended with the latest version of ISTA:
1. Electrical system troubleshooting of oxygen sensor before the catalytic converter.
2. Oxygen sensor heating troubleshooting.
3. Troubleshooting function of oxygen sensor before catalytic converter.
4. Mixture control troubleshooting.
5. Check lines and plug connections.
6. Functional check of oxygen sensor heating after repair.
It is important to complete all of the above steps and ensure that none of the following may be a cause of the fault:
1. Tank ventilation system.
2. Intake, exhaust and crankcase breather systems tight and without leaks.
3. Fuel injection.
4. Air mass sensor.
5. Ignition.
6. Crankshaft and camshaft sensors.
7. Throttle valve.
If no faults are stored and all of the other components listed and the leak tests are inconclusive, replace the pre-catalyst oxygen sensor (only if not previously replaced).
Program the vehicle using ISTA/P 3.59.0 or higher.
About the Author
Information courtesy of Mitchell 1
Information for Technical Service Bulletins comes from ProDemand, Mitchell 1's auto repair information software for domestic and import vehicles. Headquartered in San Diego, Mitchell 1 has provided quality repair information solutions to the automotive industry since 1918.
Mike Mavrigian
Motor Age Editor
Mike Mavrigian has written thousands of automotive technical magazine articles involving a variety of specialties, from engine building to wheel alignment, and has authored more than a dozen books that crisscross the automotive spectrum. Mike operates Birchwood Automotive, an Ohio shop that builds custom engines and performs vintage vehicle restorations. The shop also features a professional photo studio to document projects and to create images for articles and books.