I want to remove the under dash fuse panel. It is more than just a fuse block, it is also the under dash junction block for all the wire harnesses and has a boatload of plugins. It doesn't look to be that hard, but looks can be deceiving. If anyone can give me some pointers, I would appreciate it.

Back story -

My cigarette lighter and power outlet on the floor will occasionally blow the fuse. I don't use them that often and when I do, many time I will have to replace the fuse in order to use it. Maybe 2 weeks ago I went to plug in my TomTom and the cigarette lighter was dead. Went to put a new fuse in and the one I pulled out looked good. Replaced it anyway and still had no power.

Yesterday I got around to trying to figure out why. Checked the ground to the lighter socket and it is good. So much for the easy stuff. I checked the 12 volt wire to the cigarette lighter for continuity and it is good. I have 12 volts at the fuse but not at the pin on the junction block where the cigarette lighter wire attaches. Sooooo... I have an internal junction block problem.

Since I rarely use the cigarette lighter, if removing the junction block is too hard of a problem, my car will no longer have a working cigarette lighter.

 

I have not done the fuse box, but I have unplugged the entire wire harness from the ECM, and it was np, it looked scary, but only one way they go on. Mine was a 2008, had no issues. Was 100 degrees in my garage though, flexible wires. Not broken clips.

 

I haven't removed mine yet but I think it will come out, just some trim pieces in the way and space looks tight up in there.
Don't know if it is practical to trace the wire or just run a new wire to the cigarette lighter from the plug at the fuse panel/Body ECU.
-> I'm sure you probably have all this stuff , just posting for others if they want to follow along or need it.

2008 RX350, Gray wire, loacted at Plug 1M, pin 10, on the back of the fuse panel/Body ECU goes to the cigarette lighter.


Path of wire where it starts at the fuse and goes internally thru the fuse panel/Body ECU to the plug on the back and then continues as a gray wire to the cigarette lighter.

 

Thanks. This is a little trickier than the ECM. It has something like 10 harnesses plugged into the front and back sides. The junction box is kind of like a flat box. The fuse panel on the bottom is molded into the junction box and is the width of the box but not the thickness. The junction box dimensions are approximately 5.5" wide, 3.5" thick and 8 or 9 inches tall.

What I hope for is that I can open the thing up and actually fix it. I didn't see any screws or clips holding the halves together.

 

Thanks, I appreciate the info.

Once I figured out where on the junction box the wire is located (pin M10), I pulled the connector out and ohmed the wire to the cigarette lighter for continuity. To my disappointment, the wire is good - so much for an easy fix. When I check for 12 volts on pin M10, I get nothing, meaning problem inside the junction box.

I have the Lexus service manual and on my 07, I don't see the ECU being involved in the circuit. One of the pins on the ignition switch sends power to the accessory relay that is mounted on the junction box. The accessory relay then supplies several fuses with 12 volts, the cigarette lighter and the power outlets being among those fuses.

Access to the junction block doesn't appear that bad. I removed the lower dash panel, I call it the knee panel, and you can get your fingers on it. That's how I was able to unplug the connector and ohm the wire.

I'm not afraid to do this stuff, I've done it all my life. I just looking for info on some nasty little trap toyota may have built in. As they say - forewarned is forearmed.

Here's a photo of the car my wife had before we got her the IS250C -

 

Like a boss!
Awesome pic, hope I never have to pull out the dash, that looks like a couple $1,000 job. lol

The Body ECU circuit board is located inside the junction fuse box as you know but you are right, it is not used for the cigarette lighter circuit from what I see too.
Whole unit pulls apart by jamming up something into the plastic tabs on the side and sliding apart- nothing tricky except for a delicate circuit board and some jumper cards inside.
Only gotcha I am aware of is a delicate yellow airbag plug with tiny tabs that look like they can break easy which I'm sure you saw.

Quote: "When I check for 12 volts on pin M10, I get nothing, meaning problem inside the junction box."
Did test on my backup unit to compare for you, mine ohms out from the cigarette lighter fuse thru the box to the plug on the back(1M, pin 10, gray wire).




Here is a good shot showing the mounting holes(2 on the top and one on the side?)




That's all I got, hopefully someone will chime in who has removed it already and let us know how much of a job it is.

 

This is great info. I did not know that the body ECU was inside the junction block. I hate that the car makers integrate all the modules together.

With all the airbag recalls, maybe I should break the thing so the airbag won't deploy. Crashing into a brick wall while not wearing the seatbelt may be safer than having the airbag explode and shoot shrapnel in your face.

I didn't think to try this. It would be a good double check before pulling the junction block out. I would hope that if there is no 12 volts, there is no continuity. If there was continuity and no 12 volts, that would be a real head scratcher.

Miscellaneous comments.

I looked up the part number and it is different for JDM and NAP cars as well as with heated seats and without heated seats. I'm guessing that must be because of the body ECU. Lexus list price for mine is $1062.56. Used on ebay $175. I would probably go to the local pick & pull and get one.

When I pulled the dash on the other car, it took about 4 hours. I'm thinking that taking photos was probably an hour of that. But the first time is always longer. About 2 weeks later, a guy on the forum where I posted all the photos asked me to go to the local pick & pull with him because he wanted to replace his dashboard. He hadn't pulled his out yet, so he wasn't sure of the process. With the 2 of us working together, we had the dashboard out in 20 minutes, no lie! Knowing what you're doing and having all the tools in front of you speeds things up a little bit.

Here are 2 photos I got off of ebay -

This is the side facing the rear of the car - what you see when you remove the lower dash panel.


this is the side that faces the engine compartment.

 

This one looks like it was in a serious accident or mishandled, looking at the broke off mounting tab.
Makes me wonder what's broken on the inside!

A tip for anyone buying on ebay- I saved $100 on mine and paid only $50-60(don't remember exact amount).

Most sellers have no idea what this 'thing" is so I did a search a few different ways that got me many more results- searching for "Fuse Box" or "Junction Box" or "Body ECU".
Then I carefully looked at the pics to see the actual part# because many were listed wrong.
I sent a couple emails to sellers when I found one in good condition and said, "I would buy it if it works properly for a spare unit but I don't want to put any more than $60 into it" and Viola...

I'm keeping my extra unit in case I ever get a dreaded parasitic draw- I can swap this baby out and rule out the Body ECU.

Cheers!

 

You're right about that particular junction panel. I did an image search on Google and that was the first correct image that was displayed (you gotta be real careful on google image search). I wouldn't buy that one because A) it is damaged and B) it is too high priced. That's why I go to a pick & pull.

Here is the car it came out of:
does need a little touch up paint

 

Anyone who buys something like this...




Coming out of a car like this...




Can only be hoping to add some intermittent parasitic draws and maybe some complicated Body Electric glitching for maximum fun and excitement! hahahaha

 

If you really like working on your car, that could give you something to do in your spare time.