Hello i recently bought a C5 with 40k miles new battery and it didn't have any proems till yesterday it started dying when turned off even if its a minute of being turned off and will randomly regain power jumping it does nothing my voltage is a constant 21.7 no belt problems or fuse problems the battery shows its at 80% when tested i do not know what could be there problem but the light for a power malfunction has been going off since i also had some trouble putting fuel in it the pump kept clicking when ever i tired i was putting in 91 and it wouldn't let me fuel up has anyone else ren into this problem and how should i go around fixing this? (also the engine bay is very clean and the car has been oil changed never abused )

 

Moved to C5 Tech.

 

I would guess ignition switch.
Will you be troubleshooting yourself? Do you have DMM, test light, mad skillz to use them?

 

Wow!

 

Probably ment to say 12.7, I would try to charge battery close to 100%.