Pontiac Repair: 2005 Grand Prix problems, please help, bells and whistles, trip mileage

Question
I have a 2005 Grand Prix GT. It has the 3.8 series 3 motor in it and 3 button computer. Recently, as in the past 4 weeks and then yesterday, my car has messed up twice. Both times it did the same thing. First time it happened it did it right at start up. Then the other time was when I just cruising around town. The things that happen are:
1. Gas gauge go to empty
2. The DIC says I have low fuel
3. Trac control turns off and DIC tells me so also
4. RPM gauge drops to zero
5. Odometer and Trip mileage both say "ERROR MI"

and the only way I know to fix these issues is if I turn my car off and on.
The whole car is stock except for my aftermarket stereo. I had to install the Metra GMOS-01 adapter in order for my OnStar and bells and whistles to work properly. Then there is also another adapter so I can use my steering wheel controls with my stereo I installed. All speakers are factory but I added subwoofers powered by an amp. There is no capacitor and I have had this system installed for a year now and these problems I'm having just happened a few weeks. I'm afraid to take it to the dealership because it's still under warranty and I do not want to come to find my accessories void the warranty. So I'm looking for some advice to what my problem may be related towards and how to fix it maybe. Thanks for the help!

Answer
Hi There:

It sounds to me like you have a communication issue with the modules on the car. I would have the car scanned for codes at one of the big box auto parts stores and see what codes are in what modules and go from there. If you at least know what codes are stored you know where to start untill then you have nothing to go on.. Any kind of add on electronics on these newer cars can cause issues. not saying that is what the deal is here but it's possible.. All the computers on the car are linked together and if the communication line is corrupted between the modules what you have gong on here with this car is what happens..