Q: I have a check engine light and it reads code p1727 on a bmw 2008 328i convertible

OBD-II diagnostic trouble codes do not and, indeed, cannot identify failed parts. Once you have a trouble code in hand, what you have to do is perform a diagnostic. In the course of that diagnostic individual parts are tested often with electronic based tools. It is only at that point, when individual components are tested, that you will be able to determine if a part has failed and thus must be replaced. In your circumstance, given this particular code, the output of the crankshaft position sensor should be tested, and viewed, on an appropriate scan tool. If the sensor waveform is normal and thus the sensor is OK, the wiring is then checked. If there is nothing wrong with the sensor or circuit, in the Factory Service Manual, there is a diagnostic flowchart for trouble code P1727. That flow chart cannot be reproduced here (it’s too lengthy) but if you intend to pinpoint the problem yourself simply follow the instructions in that flow chart. Alternatively, you can request a Check Engine Light diagnostic and the responding certified mechanic will get this promptly diagnosed and resolved, right at your location. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.