If you disconnected the battery, that reboots the computers in the car.
Which means it clears any trouble codes (CEL’s)
When you are having any problems that involves a CEL being on, you should pull the codes before disconnecting the battery.

 

Yes, I know that disconnecting the battery clears all the codes. My son tried using the old key and that’s when he threw the check engine light. And then the scanner would not even hook up to the car. But the car was running. So I disconnected the battery. Used the key I have been using. Ran it around 15 blocks and it ran fine. Can all of this have to do with maybe my key. Or is there something else in the ignition.

 

My 1st impression was an ignition switch problem or wrong/bad chip key or loose wires activating the antitheft system. Getting different behavior with a different key says it’s the key, but gauges jumping around suggests bad connections somewhere.

Check recall status. Maybe an open ignition switch recall.

Go back and re-read Oldblue’s comment about tightening the fuse block bolts. Take it very seriously. Tight isn’t tight enough.

Back in September you had similar problems and U0073. What’s been going on since?

In comment #17 in that thread you mentioned that someone had suggested ignition switch work. Was that ever done?