Well even though my thermostat housing was on the lower radiator hose, the picture was quite helpful just to show me what to look for when I was trying to find the ground. So thanks!

So yesterday, I checked for codes again after the battery light failed to come on when I turned the car on, and I got one - I'm pretty sure code 20 (2 longer blinks of the CEL, no short ones), which according to my service manual is the Electric Load Detector. So my new question is: does the code mean there is something wrong with the ELD itself, or does it just mean that the ELD is detecting a problem? And where would be the best place to start looking for that problem? Any help would be appreciated.

Jim-PA- that is the pic from "techauto" on the 4th gens.

OP-If the tach is involved - YES - check the coil and ICM. There is an output from the coil that drives the tach...so if it starts bouncing as/when the issue happens then that is an indicator as to where the issue is...IMO.

Ok, thanks. The ICM was replaced about a month ago, so I guess I'll take a look at the coil next. Any ideas about the ELD code?

My car had the same problem as yours. It was my ICM. I replaced it and all was good. There are 4 spade connectors on the ICM, make sure they fit good and snug. Could be one of them is a little loose.

Good luck

Did you ever figure this out? Mind does the same thing. I can't figure it out and hate to get rid of it

Solved
 

Hi, yes! We did figure it out. Sorry, I should have posted the solution long ago. After messing around with it a bunch and replacing some parts that probably didn't need to be replaced and not getting anywhere, we got a wiring diagram, took a closer look, and found a loose engine ground wire. That was it. Fixed the problem 100 percent. Good luck!