Brand new body ecu from Toyota, less than a month old and it's already acting up again. Or, maybe? That's the question. I'm worried it is something else.

2000 SR5

I had posted before about some strange Gremlins I had, issues with the door lock button, dome light, key cylinder light, and the door buzzer stopped working... Also had an issue with the cluster freezing but I have no proof these items are related. Talked to some people and read dozens of other posts and threads, came to the conclusion I needed a new body ecu. The "junction box" under the steering wheel, left side.

After replacing the body ecu, the problems were 95% fixed. 95% because the Dome light still didn't work at first, but when I turned on the map lights it caused the dome light to flicker to life and it's been working ever since. So then it was 100%. Not sure what that was about. But there was an insta tly change with the new body ecu, door lock buttons have been working consistently since then.

As of 3 days or so ago, the damn door/key buzzer and the key cylinder light have stopped working... What on earth... This makes me feel like there's some kind of electrical problem, but as far as I can tell nothing really seems to go outside of normal voltage range... At least according to obdii. Is that to be trusted?

Anyway, I'm out of ideas and I really don't want to drop money on another body ecu. (In case something is making crap burn out) Thoughts? If it's not the body ecu... What could it be?

Post where I talked about swapping it:
Body ECU swap, problems fixed

Post where I had my cluster issue:
Found Speedo and Tach stuck, odometer displaying - - -

I had a rule of thumb when I was an auto tech for 13 years: if you think it's a computer, it's not a computer. 13 years working on predominately Japanese vehicles from the 90's to 20-teens. I think I replaced one airbag "computer" in a Nissan. It was more of a sensor but that's not the point. It's been my overwhelming experience that computers in general and especially Japanese and ESPECIALLY especially Toyota computers don't fail.

So yeah, it's not the body ECU. The scan gauge obd2 does zero for any form of actual electrical diagnostic. You need a wiring diagram, a multimeter, and a better foundation on the flow of electrons and the related principles. All due respect.

Based on the very limited description given for your complaint, I would guess it's some sort of switch in the ignition lock cylinder which sends signals to various electronics. It could have been the body ECU. But 2 bad ones? Naw. Especially when replacing it gave you "95%" better results. That's not a repair in my opinion.

Why did you replace the Body ECU? Was there any fail that was assuredly caused by it? Because the key lock buzzer, key light, and dome light are controlled by the combination meter, not the Body-ECU.

I would guess your issue is in the combination meter or you have a corrosion issue in one of the plugs or junction boxes that the circuit goes through. Like the man said, you need to take a wire diagram, a meter and trace the dang circuits. Then you would at least learn they don't go through the Body-ECU.

I'd get you started by posting a wire diagram, but your post does not contain year which makes it impossible to give any detailed electrical help..A link to the original thread would have been nice, too.

My point is I am worried if there is some kind of electrical fault that is damaging things. When I replaced my fuel sender the old one had physical burns on it's electrical connections. That's was something else that worried me but I couldn't find anything that could cause it.

As far as obdii I'm just talking about the voltage overall. Like in general if there was an over voltage situation then that would explain a lot.

In the previous case, it was the body ecu, replacing it fixed the door locks, doom light and buzzer. The 95% was due to the dome light bit working until I turned the map light on. again making me feel like there's some kind of electrical issue that I can't pin point.
But after that point everything was behaving perfectly so I thought maybe it was nothing.

Look, I have no idea why you both decided to post with jerk-ish attitudes. I'd rather you not post at all. I have no idea what point you're trying to prove but there is no need for it. We are all here to help each other and talk about cool truck stuff. All due respect.

I posted at like 2 am or something, forgot to add the year. Not the end of the world. 2000 SR5.

The body ecu DOES control the locks for sure, you can hear it when you toggle the locks. The relays clicking is what I am referring to. I went through hours of reading threads and gathering information that all came to the conclusion that it was the body ecu. Just to confirm though, are we talking about the same thing? The little junction/fuse box under the steering wheel on the left side.
if the body ecu truly does not effect these items, why did replacing it fix everything?

I've never seen anything mentioned about the combination meter, but I will look it up to learn about it.

Edit combination meter is Toyota talk for cluster. I see that a lot of things pass through there, but it seems odd that not everything is effected. Also still curious if the burnt fuel sender is related. But I can't imagine the gauge would work fine 99% of the time if it had a major issue.
More research required.

It's in the Geneva Convention, look it up!

-Ricky Bobby

Alright alright my apologies for being a d!ck. I really don't want you wasting more money on an unlikely repair. I see it all too often where people throw parts at cars without any attempt at actual diagnosis. And it sounded like that's what already happened and was going to happen again. The quick answer is there may not be a quick answer.

That being said, I'm honestly recommending a wire diagram and a multimeter. You need to get some hands on testing to have a chance. I no longer have direct access to OEM wiring like I used to so I can't offer any direct specific help unfortunately. All I can do is be a snarky keyboard warrior to dissuade from a potentially poor decision.

If you get your hands on wiring or operational info on those particular systems for that particular vehicle I'll be happy to try and guide you in any way I can. Until then, I'm about as useful as a passive aggressive comeback sprinkled with a dash of irony.

Ah..yeah I'm sorry I reacted a bit poorly. Just wasn't having a good day at that point.

I'm going to town today to get a multimeter (I just have an ultra shitty one that can't even test for continuity) and I downloaded some of the diagrams. My only current question is... Are there more diagrams that what the FSM shows? I only see a few mention the interior stuff, lights, body ecu, etc. I've seen a few pictures online ones that look a lot more advanced, but I'm not sure what year they are for. I mean maybe it's close enough or the same, I just figured it would be from the fsm. Haha

Well, start with the wire diagram. I didn't say the door locks were not controlled by the Body-ECU...they are. But your current issue is buzzer, dome light, and key light, and THEY are not. See attached EWDs for 2000, which is why I needed your year.

Let me give you some hard-learned advice. Stop trying to logic your way to the problem if it is not simple, and just trace the dang circuits one at a time. You will save money, time and aggravation.

Attached Images

	208 Key Reminder And Seat Belt Warning.pdf (47.0 KB, 44 views)
	106 Interior Light.pdf (58.0 KB, 52 views)

Hey Durk I appreciate the files and stuff man. Yeah like I told the other guy, I wasn't having a good day when I replied, sorry about that. Just a bit too much stress going on...

Alright, so! I bought a multimeter today, although I may go swap it for a Klein or whatever the other brand is called. I got a southwire but it doesn't seem to tell resistance correctly... Eh

These guys are pointing the OP in the proper direction. Circuits are going to have to be traced and verified that they are not shorting to ground nor other circuits.

Many times. Body lifts have been known to stretch and break the fuel pump tank connectors or wires in top of the tank.

Folks putting in amps and accessories damage the wire boot in the driver side fender wheel letting water basically get in and get the wiring harness connectors that are all in the driver side kick panel side.

Sadly it gets very expensive just swapping parts without verifying that's the issue. Being these rigs are now 18 + years old.

It would be best if possible to trace and verify that the circuits are good because corrosion causes resistance which drops voltage and can damage circuits as well.

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Yeah tracing is the next step, although I have to go and swap out the meter I got. The first one is bad...woo....

Are there and write ups on tracing? Just curious, physically, how to trace some items. I'm assuming I need to open the dash. But am I just tracing the cluster by its' self? If this makes sense.

Basically you have to be able read schematics. Use a multimeter probably. For write ups on basic wire tracing maybe you tube may help on that quest.

Buy half decent equipment if possible as nothing worth then bad equipment.

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Oh yeah I mean I get the basic idea. Checking for continuity but also resistance. I'm just wondering, am I taking the cluster out and bench testing it so to speak?

Also yeah gotta go back and get a different multimeter. Southwire any good?

Not sure about southwire..

Checking continuity resistance as well as verifying wires are shorted by insulation rubbing off as well.

Very common to have the wires short and break in the door jams as well as the tailgate. Causing issues as well as a few circuits are always hot in the tailgate ( Stop lights)

99 and up have the Communication multiplexer in them as to why users were asking the year as 96-98 do not have the communication bus in them. The multiplexer are slightly more complex but your checking wires at this point so not critical at this moment in time. :-)

over the years I have had a multiple of electrical problems...and thedurk is a prime resource.
your problem might be more complicated...but the last electrical issues that I had with interior lights and door locks acting up was a door switch shorting out. they call them courtesy light switch actually. surprising how many of the electrical things are linked to that. But you have a short someplace....my 2cents