I have a 2003. While I was going to get dinner i noticed my fuel, temp and oil gauges were all not working. Then i noticed my fog lamps, power locks, keyless entry were also not working. Then after i turned my car off the radio display, the ignition light and the inside door(power windows, power locks, trip re-set, etc.)lights would not go off. Even after opening my door locking the doors they would just stay on. I obviously have no idea whats wrong since im on here asking for some help. I disconnected the battery so it would not die. Please any help will be greatly appreciated!!! Thank You.

That is indeed a mystery... just out of curiosity... how old is the battery, have you done any work to the car lately that could result in a grounding problem, or loose cables anywhere, or anything that might lead to this...

With everything you've mentioned, you might want to take the car and get a Tech 2 scan done. This will narrow down what might be the cause. Otherwise...you'll be taring the car apart looking for a ground problem, module problem, data bus problem or?

You may want to try these tests. With everything going nuts it could be as simple as a bad battery cable.

https://www.gmforum.com/t279494/

https://www.gmforum.com/t279492/

As far as i know the battery is probably as old as the car so 6 yrs old. No i have not done any work on the car lately that would have caused a grounding problem or anything else..By the way thank you everyone for the help.

Ok after little tampering..disconnecting the battery re-connecting it everything is working fine..hmmm..idk?

With all the electronics on these cars, they like clean power and good grounds. Glad you were bale to get it solved.

For the recored, corrosion problems are common. I clean my battery connections 2 times a year.