1) Be as descriptive to the make/model/year/engine size/fuel etc as you can.
2) Feedback is king,describe the syptoms/noises/area/affects to the vehicle as in detail as possible.
3)Inform us of any work recently carried out,it may be associated.
4)most modern stuff needs code reading,I have one similar to this
I find sometimes when my snap on one wont go in this does,go figure
Please read the instructions thoroughy before using though,because you are opening the ecu with it,you need to close it as well.
Make a note of any codes before clearing,we do quite often get what is called ghost codes,which means a non working part will also make another not work,so you have to read between the lines sometimes.
I think that is it for now.