Any help would be greatly appreciated. This is bringing back nightmares of an Explorer I finally ditched last year after failing to diagnose the gremlin. Here's the story.


My first Vette
I bought a C5 a few months ago with 29k miles on it. I replaced serpentine & AC belt mainly because the chirping was annoying at startup. No other problems. Driving a 1-2x a week for an hour plus in that time. The only other thing I've done which was well over a month ago was by one of those FM transmitters so I can bluetooth my music through the cigarette lighter. I always pull it out when I'm done driving.

The battery is a year old from the previous owner who babied it. Wife and I took it two long rides two weeks ago no problems.
In the last week it will not hold a charge. I've looked for lights on, put the phone in the trunk on record, glove box, etc. Always goes black.

I charged the battery the last few days. Get it to 12.7 turn it on and it goes up, so I think the alternator is fine. Drive it each days and then it would be dead the next day. I thought it was draining overnight which I thought was extremely fast for a parasitic draw, and tonight after I drove it was already down to 12.11 after I turned the motor off five minutes before and it would not start a second time. So it is draining rapidly. Could it be the alternator pulling it down with it off? Again, it is dropping so fast when the car is off.

The only other non factory things in this car, were a 12 disc cd changer which I unplugged after these problems started, and one of the weirder things is an aftermarket amp in the trunk that isn't lit up in any way, so I'm not sure it is even working. What is odd, is the Bose amp is still under the footwell.

I did a touch test on the relays. The 42-IGN relay was hot and stayed warm. Switch 37 in footwell was warm but cooled. The fact I couldn't restart the car after driving it is making me think it might not be an electronic gremlin.

I also had a check engine light come on, but it went away yesterday and came back.
Only code I'm getting is P15158 - Electronic Throttle Module to PCM.

 

My first Vette

 

You need to voltage drop each fuse looking for what may be causing your drain...if you think it's the alternator just disconnect the B+ cable and check the draw...we don't pull fuses anymore.