Dash went crazy

First check and see if the dash light dimmer control on the headlight switch is turned down all the way, which shuts off the dash lights. As far as the gas gage goes that is more then likely a defective gas tank fuel level sending unit.

Has the light been going to out slowly or happened all at once?

Have you turned the Dimmer all the way off or did you blow a fuse?

There is a Wheel or know that you can adjust the Dimmer on the Gauges, check and see if someone accicently turned it all the way off..

Wiring problem under the dash. Could be a ground issue as you said. You need to get under the dash and check the grounds.

Under the carpet, near the gas pedal, there is a ground wire screwed in, and that connection is going to be corroded. Clean up the connection and be sure it is tight. I just went through this with my 97 Seville. Fixed every electrical problem I was having with lights flashing, gauges going crazy, etc...

please keep me posted as well, ALL my gauges are doing the same. First the gas, filled it one day and it fell all the way and light turned on, then my themostat, freaked me out, thought i was overheating,...NO just the guage, NOW my spedometer is stuck on 120, and my RPM's are acting crazy. i have read tons with this same problem, WHY WONT the manufacturer DO SOMTHING??

bad ground from the sensr unit,bang on the fuel tank and see how it behaves to confirm

make sure u didnt break a wire, there are sensors on the brakes, make sure theyre plugged in

I'm begining to think the problem is related to erroneous speedometer input data, ( could even be a trans speed sensor, or the speedo itself ) which falsely makes the TRACTION CONTOL SYSTEM think the drive wheels are actually SPINNING, and losing traction, causing the light to appear. Hopes this helps

try disconnecting battery terminals for 15 min and reset computer

check your cluster