For emphasis, get the EASUnlock software, a laptop and a cable. It's a start and will tell you what's going on.

Seriously consider a Nanocom too. They're bit of outlay ($540). It will pay for itself in avoided heartaches and dealer trips.

For a few days, I've had 'airbag fault'. Hooking up the Nanocom told me "The drivers airbag has an open circuit - Permanent". So now I know exactly where to go. Especially since I'd recently swapped out a steering wheel. Turns out that wasn't the fault, nor was it the other likely candidate, the rotary coupler (aka clockspring) but in fact a connector inside the dash that just needed a squeeze to fix. How long would I have looked for that if I just had the message centre error to go on?

The Nanocom will do all ECUs in the car and allow you to set a lot of things.