Q: How many camshaft position sensor are on my 2012 BMW 328I 2.0 turbo

There are two camshaft position sensors on your model. Both position sensors, as well as the crankshaft position sensor, should be tested using an appropriate scan tool or automotive scope to determine if they are functioning. Due to the availability of scan tools and other diagnostic techniques, it is almost never necessary to replace parts on a "trial and error" basis. Also, it is very costly and wasteful to proceed that way. The best thing to do is have the vehicle fault actually diagnosed (pinpointed) and then replace only those parts which are confirmed by testing to be faulty. In your circumstance, the best way to proceed is to request a check engine light diagnostic. A certified mechanic from YourMechanic would use a code scanner to retrieve the specific diagnostic trouble code(s) from your car’s PCM that have caused the check engine light to illuminate. Using those codes, the appropriate individual vehicle components or sub-systems (often a sensor, circuit, and the like) are then carefully tested, based on specifications set forth in your car’s Factory Service Manual, to pinpoint the cause of the fault or the reason why the check engine light has illuminated. Once the faulty part or component is identified, it is explained to your satisfaction and the mechanic will let you know of the cost to repair. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.