I took the VETTE from the shop and later that day I got a message REDUCED ENGINE POWER,SERVICE TIRE MONITOR SYS.,LOW FUEL-gauge went all the way down,SEAT BELT sign was ON,Service ABS-ABS was on, SERVICE VEHICLE SOON....it also happened last night as I was driving.This morning the battery voltage was below 13V when the key was set to ON-it is an OPTIMA red top so no leaks, was replaced about 2 years ago. It might be my grounds need to be cleaned or that the battery voltage was low or torque wasnt right so it gave all those messages at once.I haven`t checked for codes yet.Could this be related to the FUEL TANK replacement and they didn`t reconnect some stuff right or something else ? I know there was a post about this and I will search but if you have any ideas let me know so I can refer them to the shop-I am taking it back as of now.

Ok, here are all the codes-I erased them and will go for a ride-tyhey were all in History "H"

10-PCM P1626H,
28-TCS U1301H,
40-BCM U1255H,U1096H,1016H,
58-SDM U1301,
60-IPC U1255H,U1016H,U1160H,U1064H,U1088H,U1040H,U1176H,
80-RADIO U1096H,U1064H,U1016H,
99-HVAC U1064H,U1096H,U1160H,U1255H,
AO-LDCM B2264,U1255H,U1064H,U1016H,U1096H,
A6-SCM U1300H,U1255H,U1064H,U1016H,
BO-RFA U1000H,U1255H,U1064H,U1096H,U1016H,

So I cleared all of them and will go to take it back to the shop and see if they messed up something with the Fuel Tank fix.

Battery it's charge or connections would be first on my list. Enough juice? connections clean and tight?

Since you just had work done.....check the terminals that are screwed into the actual battery. If they're tight, I'd have the battery load tested, but I'm guessing the shop that did the fuel tank loosened the battery wires and didn't put them back on tight enough.

My car had a lot of seemingly non-related issues like yours after some major maintenance. Turned out to be an electrical connector that hadn't seated when everything was put back together. Unfortunately, there are lots of electrical connectors in the car. If it is not obvious around the areas where they worked, I would take it back and make them fix it.

I got the VETTE back from the shop-They said they needed to replace the FUEL sensor and asked for my old tank back-after the job was done they said everything was fine now. I drove it and later that night my FOB wouldnt open the doors-there was no reaction from the VETTE at all. I manually opened the door and tried starting the ignition-wouldnt start...got a message REDUCED ENGINE POWER and LOW VOLTAGE, LOW FUEL. I tried starting again and it did Start. I have no clue what they did but in my opinion-they have no CLUE what needs to be done. I never had any of those messages before the Fuel tank replacement-If I disconnect the battery and reconnect it would it reset or should I check the grounds-what do you guys think ??? Could it be the battery itself-it is an OPTIMA red top 2 years old ???

It probably is the charge of the battery.

Like leadfoot says it is probably a charge issue. Since you're getting so many seemingly unrelated codes I'd start with the battery. Taking a look around at your grounds and connectors wouldn't hurt.

Check my post re similar problem a while back - took off the battery connections, scraped everything ultra clean and reassembled with lots of Vaseline - no issues since. It's easy with these terrible side mounts to not have the round "terminal" on the end of the lead seated into the battery properly - sometimes it wants to be on an angle, then although the bolt seems tight, you will get intermittent "iffy" contact. Wish GM would use proper battery terminals like everyone else.

I took the VETTE from the shop yesterday and it seems to be fine for now. It was there for 3 weeks and the owner said they cleaned the grounds like I suggested and connections to the PCM etc. There was no Charge for that and hopefully the problem is solved. Will have to wait and see.