Anti-theft red light on solid when key off

Re: ECU/ECM: I suspected it might be Urban Legend fantasy, but even without such a safeguard, taking on this swap project is nothing to take lightly. I have only partially removed a dash twice, both times on elderly Volvo's with bad evaporators. The old plastics holding things on the firewall were a challenge. Even taking my time, and being egg-shell gentle with the removal wasn't good enough for re-assembly here and there: I had multiple electrical glitches and things that rattled or squeaked and the dreaded electrical phantoms with things not coming back to life. Getting to this Tacoma ECU and its relatives to r&r, sounds like a similar adventure, except for the sophisticated (expensive) electronics in place to deal with these days.

 

As I’m sitting here thinking out loud…any chance the 4WD ecu could be the culprit on the parasitic draw? Or does that not power up until you turn the ignition? I thought it went through the 20A fuse in the cabin fuse panel. But here’s to hoping…

 

I've done quite a few dash jobs, most aren't too bad.
I haven't done a Tacoma yet but I have done a 2nd gen Tundra and there's alot of stuff to remove.

No the 4wd ECU doesn't have a keep-alive power, it's only powered when the key is on.

 

Unplugged at actuator. TL1 still at 0.63 v. But TL and TL3 went to 12V. They were 0 V before I unplugged.

 

Leave the Transfer Case Actuator unplugged and unplug the 4wd ECU then check TL1 for a short to Ground.

 

Unplugged from ecu and checked continuity between TL1 and a good ground. Zero continuity.

 

So the 4wd ECU is smoked, I guess you could take it out and pull the board out to see if you see anything.

 

That’s what I figured. Just ordered the alternator from Toyota. Advice on ordering a new ECU? Does it need to be programmed or would it just be plug and play?

 

Just get a used one, they can be had for around $100.
Just need to match the part number, no programming or setup required.
What part number is yours?

 

89533-04020

 

So it's 05-09 4wd without Rear Diff Lock.
Looks like around $400 new/ $200 used.

https://www.hollanderparts.com/used...9158-transfer-case,-(rh-dash),-id-89533-04020

I can't find a clear answer if the newer one (89533-04021) would work or not, those are cheaper used.

 

Back to the alternator draw…I have the 1GR-FE. I noticed on tue wiring diagram that there a line to the Body ECU. I’ve let the truck sit and parasitic draw is now down to 13mA with the alternator unplugged. So I must have been taking the readings to early and not allowing the All the computers to go to sleep. But plug I. The alternator and back to 300 mA draw. So I started doing some testing there before I go replace a new alternator. This diagram shows four wires for my engine w/o towing. I only have three in the alternator plug. One of those three (looks mint green but it’s hard to tell, the other two are white) the mint green one, has continuity to ground. Does that make sense?

 

The one going to the body ECU I haven't figured out for sure what it's for but my hunch is that it allows the Body ECU to turn on the Charge Warning Light independent of the alternator if the battery voltage is too low.

The Light Green wire is ignition power to the alternator regulator, your gona see a path to ground on it when the key is off because there is alot of stuf connected to it.

 

Got it. What’s weird is I don’t see that grey wire. There’s only three going into the plug. It shows I should have it ( by the *3 symbol). But I don’t see it at all. I’m assuming it still works without it. So weird.

 

Just put a flashlight on it. I think there’s a light grey, a white and the green. So I do have the light grey. So maybe I’m just missing one of the whites. That makes me feel better.

 

You should have the Grey wire in Pin 4, you won't have the Blue wire in Pin 3 though.

 

Oh the whites are on 1 pin. I didn’t notice that. Sweet. Don’t know why I’m still thinking about it…alternator already on its way!

 

Did you find a 4wd ECU?

 

Is it poop ow the ecu bo

 

I did. $400. I’ll let you know if that clears the issue. Comes in Tuesday.