hii have resently bort my bmw 323i. witch has now failed its mot i am trying to fix the issues myself but am having difficultes as my air bag light is on, i bort a diagnotics divce wicth reads srs codes but it will not read them on my 323. i no i have 2 diagnotic port on the car the 20 pin under the steering wheel(witch i have been trying to use) and the older 16 pin in the engine bay. should i be using the 16 pin? or is there something wrong with the 20pin connector?? ANY HELP WOULD BE MUCH APPRECIATED.