I have massege on my dash default withholding system and my car D'not start....What is the problem

Crank shaft position sensor is bad. This is the most common failure. Its location is on the rear drivers side of engine, where the transmission bell housing mates to the engine, only one small bolt and a two prong electrical connector hold it on. Usually will not throw a trouble code. If you remove it you can test it with an ohm meter, will have an erratic reading or read open loop, can malfunction intermittently or permanently after parking vehicle and won't restart. Applying some heat source to it during ohm testing with a hot air heat gun will usually cause the sensor to read open loop if your not sure if its bad or not. This reply is probably way to late, but I just happened to come accross it while online. Harry (master certified MBZ diagnostic tech) , aftermarket stereo? dome lights? car alarm? Use a multimeter and see what fuse has power draw when car is off. , Hi 1) Turn the key to position #1 and make sure the menu in the instrument cluster is on the total mileage and trip mileage screen. 2) Press the 'accept call' button and hold it. Then press the 'ok' button, this will take you to another menu screen. 3) Scroll around to find 'assyst plus', hit 'ok'. 4) Find the 'full service' option and hit ok 5) Confirm service with the ok button, it will then say 'service confirmed'. 6) Use the back button to scroll back out.