Jchavis71

Ive got a 2000 GC 4.7. When I try to start it, all the lights die. Even the seat belt light is barely visible. The battery was replaced last year and is currently holding at 12.7V. I also cleaned the terminals to a shine and made sure they are nice and tight. Sometimes when I try to cycle the locks with the remote, it will also make the car completely dead too. Even a dead battery should be able to unlock the car, right?

What the could cause this? Thanks guys.

dave1123

Check your positive(+) battery cable clamp. It may be wrench tight, but not be putting any pressure on the battery post. The lead stretches and the ends of the clamp come together so the bolt won't tighten anymore, but it doesn't put pressure on the post. Try to twist and pull the cable off without loosening the bolt. You may be surprised.

If this is the problem, you can do what I did. Take the bolt out, cut the slot wider with a dremel tool, and put it back together. Just don't retighten it until the slot disappears. That would start the cycle all over again.

Jchavis71

Thanks Dave, I've read your posts before about checking this, so I made sure that I did this before claiming that the posts were tight. There is a gap on the terminal after tightening. But even with a bad connection, wouldnt the gauge lights come back on? After I try starting it, it just sits like the battery is beyond completely shot, but it still reads good on my DMM while connected to the car.

dave1123

Check the small battery wire that runs to the PDC. It supplies all the current for the vehicle except the starter. It may have a bad connection either at the PDC or the battery cable end itself.

Jchavis71

What is a PDC?

dave1123

Sorry. It's the Power Distribution Center. It's the fuse/relay box under the hood. There's a large red wire running from the battery cable clamp to it.

Jchavis71

Wow Dave, I officially feel like an idiot for not even thinking about that...and I'm an electronics technician. I will definitely check that tonight.

Jchavis71

Confirmed...my buddy forgot to tighten down that cable when we put the battery tray back in. Thanks, Dave.

dave1123

There is one item you should be aware of that wasn't involved with this problem, but you should be knowledgeable about. Underneath the battery, there is a thermal sensor that signals the PCM to cut back the battery's charge rate when it gets hot. If this sensor goes bad, it will cause the alternator to not charge the battery the way it should. I hope you reconnected it when you put the battery tray back in. It's a little thing most people aren't aware of and I'd hate to see you replace the alternator for no reason.

Jchavis71

Yup, I did a lot of research about that because when I had the engine running, I moved the battery and it killed. I thought that it may have been a pressure switch. It was caked with dirt when we pulled the tray out and I cleaned it thoroughly. Nonetheless, I know its plugged in and has a better connection now. The voltmeter on the gauge even went up 0.5V.