I have a xo vision x349nt deck in my car and i have subs and an amp hooked up also, the problem i am having is when i turn my car on the amp initially powers on but only for a second then turns off but the blue led light on the amp stays on after the red power light intially turns on then quickly off. any thoughts?

How is the system connected? Are you using aftermarket amp or factory amp, check speaker wire from amp yo subwoofer, and volume levels kn the amp if aftermarket.

try another rca output on stereo

Make sure and check the RCA wires in the back of your radio that send audio to the amp and make sure that they're connected to the OUTPUT/SUBS RCA's and not an input rca's. Also, check your ground and make sure no speaker wires in the subs are shorted. Try one speaker at a time see if that helps.

Model LCD 7'' :Innolux AT070TN07 + Touch panel (unknow)

Don't ground it. It's the amp remote wire. You're grounding 12V. Go here for the wire specs. Hopefully you haven't shorted anything in the unit. http://www.xovision.com/pdf/XO1915BT.pdf

radio shack online or crutchfield.com may have what you need

Get RCA "Y" connector, radioshack, etc.
Or, plug your 1 RCA into the amp and wire to sub from amp

well first i recomend checking with local laws prior due to it could be illigal.... now to you awnser 3 solutions for you A. try connecting your brake wire to the head units harness on ground B. you will need to run power to a switch hook the brake wire to the other side and togle the switch a few times every time the deck turns off and on or C. check ebay and other sites for a "black box" this will simulate the pulation from your ebreak making your deck think its on this can be a costly part anywhere from 35 to 180 dollers

According to the specs for the xo 1945- the output is; 50W x 4 Max Power Output , and I do not see a pre amp output listed. So I think to connect subs, you will need a separate AMP.
The way this works; the rear speaker wires from the xo 1945 hook into the Add-on amp, for example a 4 channel amp. In a 4 channel amp, the rear speakers come off two of the channels of the add-on, and the subs come off the other two channels. There is also the option of bridging two channels for more output power to ONE sub.
You did not mention what size sub(s) you were thinking of adding, but keep in mind that the ox 1945 puts 50 watts MAX per channel. So, if you add two 12" subs and a 1500 watt amp to drive them, your total sound is going to be very uneven.
If you go on line and look up auto audio or amps, you'll get a good idea of all the Sub and amp options that are available.... Hope this helps.