Jerking and putting.symbol flashing.

get your car fix right now
Pontiac Grand Prix 2004 Owners Manual Download

Look for a burned fuse or a fuse link which is inder the hood.

Used parts such as starters and altinators don't last. It might **** but it sounds like you need to buy a new starter,altinator, and battery. Or just start with buying one at a time.

Check the mixing valve under the dash should be behind the glovebox

a loose connection

I have the same issue. Did you ever find a solution, i need to fix this problem asap too.

change the back light

It's under the hood, on the driver's side, under a square, black box with a lightning symbol on it. Loosen the flower-shaped screw that holds the lid of the box down, remove the lid, flip it upside down and when you look at the inside of the lid, you'll see a map of all your car's fuses. There's also a fuse diagram on the very end of the dash, but it's accessible only when you open the driver's side door. When you're driving, that end of the dash is blocked by the closed door.

at the bottom of mirror there is a square symbol with vertical lines that look like wriggling snakes, it is the same symbol used for the heated back glass.

Check under the dash below the cluster/dash area for a disconnected/broken wire.