Clicks no start

[RCH]

Hi, It's been awhile since I've been here.

2007 LBZ bought new, I've put just under 90k miles on it. Garaged since new. It has been running great no issues then yesterday I went to move it and when I turned the key I just got 3 clicks and nothing. I charged the batteries over night. All other power works fine.

It also changes oil life monitor to 0
But it doesn't affect the fuel filter life.

I did protect the harness coming from ecu years ago and it looks ok. I checked and cleaned the ground on the frame under driver's door.
Would the transmission neutral stop switch cause this as well?

It could be the starter but it has shown no signs of failing, don't they usually go out gradually?

Would appreciate ideas, I'm going to go more in depth with grounds next.

 

[2004LB7]

I'd try disconnecting both batteries first and see if it makes any difference. Aso make sure both battery terminals are clean and tight. Obvious stuff. Ground from engine to frame too

If it's the park/neutral switch, you can try it in neutral to see if it makes any difference

 

[darkness]

How old are the batteries? Did you load test them?

 

[RCH]

Thanks for the responses, the batteries are only about a year old. Tried starting in neutral no change. I did remove the GM battery terminals, cleaned them and reinstalled. Truck started right up. Those gm side post terminals hide alot of crap under them.
I ordered 4 side post studs so I'll go that way, at least I can see what's going on and there will be more contact area.

Thanks again,
Richard