Strange Electrical Issue - Accessory Fuse/Body ECU

Hi. I've got a '97 SR5 that started doing some strange things recently.

The aftermarket radio from PO has always had a bit of background (grounding?) noise that comes through the speakers. I've owned it for about 15 months. In the last month or so it would get pretty loud every once in a while. Then about two weeks ago I started my truck one day, the noise was really loud, then the radio shut itself off, rebooted, then did the same thing.
I noticed by accident at different points that the noise was once temporarily reduced by hitting the brake pedal and another time by accidentally putting down the the passenger side lock, which signaled electrical issue to me.

Then it happened again on startup and the idle was odd, kind of stumbling. Ugh.

My son's dad suggested the ICV as a possible source of strange running issues, so cleaned that (definitely needed to be done), put in new gaskets. Made a difference, but didn't fix the problem I'm having.

So I pulled out my multimeter. Found that the 15A accessory fuse in the junction block has the following voltage readings:

No key, 0.3V-0.4V
Key in acc/on, 12.2V
Engine running, fluctuating around 1.4V-1.6V

Same readings on accessory wire in ignition switch. The part that really concerns me is that with the engine running all the fuses in the junction block/body ECU area have the same fluctuating readings around 1.5V, but don't seem to be impacted with the key in accessory or no key at all.

I'm still trying to sort out the wiring diagrams, but was hoping someone might have some insight to offer, ideas of where this might be coming from or things for me to test. I don't really understand how all the body ECU stuff interacts and operates.

A couple of others things... I initially suspected the aftermarket radio wiring, but that looked pretty clean. And, it still had the problem with the radio, clock and cigarette lighter disconnected. Also, the noticeable problem (loud speaker noise, radio shutting down, stumbly/just not right engine) is very intermittent, but when I re-tested those fuses tonight I got the same numbers without those things happening.

Could it be the ignition switch? The body ECU? An exposed wire somewhere?

Any help would be greatly appreciated.

 

Anybody have any clues as to what might be going on?

 

Check all your grounds. If I understand what you're saying...it sounds like a bad ground.

 

Thank you.

I haven't specifically dealt with a bad ground yet, so I wasn't sure if it would cause something like this, but I guess I should just check them upfront from now on.

And pretty much all the electrical problems I've had so far (mostly with my deceased dad's BMW E36) have involved multiple control modules, which has made it difficult to diagnose for someone trying to teach themselves.

I'll report back on what I find.

 

Well, it's always a good place to start. Check all grounds. Then check all main power connections. Toyota ECUs are pretty tough so I wouldn't suspect it until you rule out many other things.

When you have multiple electrical gremlins, start from the source and work up.

Used BMWs are misery.