fsuguy

I have a '92LS400 and can confirm that this model does not have the separate FP ECU - instead it uses the FP resistor; the available literature indicates that after 1992, the LS400 utilized an FP ECU... so the LS400 models from '93 on should have a separate FP ECU.

Yamae

What is that literature? Could you show it?
Toyota engineers never designed the separate ECU for the FP. Every LS400's FP is controlled by the main ECU.

dicer

http://www.lexussouthatlantaparts.com/showAssembly.aspx?ukey_assembly=767427&ukey_make=1082&ukey_model=15669&modelYear=1994&ukey_category=21749&ukey_trimLevel=19107

Here you go Yamae, this is the parts book for a 94.
Oh and this may be only on US cars so you may be correct as well.

kthomas325

Hi there, 3 weeks ago out of nowhere my 98 LS400 with 252k started to have its temp gauge, outside temp/thermometer near a/c vents and then a/c compressor just just quick working intermittently. This started happening on my drive from Daytona to Orlando. Must of the time it would just be the water temp gauge falling down to off/cold then popping back to life. If it stayed down for longer than 8 to 10 seconds the exterior temp would stop reading and only show blank. If this lasted up to a minute or so then the a/c compressor would stop. I have owned the car for 2 years and put about 30k miles on it. New battery, fan clutch, every mount under the car, timing belts, cam seals, OIL SEAL, anything and everything has been kept up except it has the vague on center steering do to worn something in the top of the rack between firewall and steering wheel and of course it has vertical play in the wheel to but just a bit. Both tele, and scope work with wheel. After running into your great write up and ready about some similarities with the windows and a/c, I had my ECU pulled out from under glove box and sent off to illinois place to replace possible leaking capacitors. They called and said everything was perfect on the board and sent it back. Since re-installing those problems are gone..------ A/C, Ext Temp, Water Temp, are having zero problems ..BUT ....now.... the drivers window switch works the sunroof works, cruise works, everything except the windows, the power door lock button, the door lock key fob, sometimes the trunk lid release. the weirdest thing is though the other door window switches appear not to work unless u open door and try it again, then it will work as supposed to just never from drivers door. Also when i open door with the dome light set to come on when door is opened, it only turns on the bottom door lights, not the main overhead dome light. Any thoughts? I wasted 3 weeks and $89 thinking i had bad capacitors. Is there some fuses im missing or what? Please help ole wise one because i love my LS and i dont know what the heck is going to on!!
TK

Yamae

Judging from your statement above, the MPX network body computer is not working properly. Because the dome light is controlled by that. Didn't you stress the MPX network body computer while dealing with the main ECU?

OKSTANCE

got a newly rebuilt ecu...fixed every issue I ever had...which was a lot..and made no sense..

96UCF20

What sort of issues did you have prior to installing the rebuilt ECU?

dicer

And for what year car?

ZionXIX

Hello all,

I am new to this forum but I've been a lurker for a while. This thread inspired me to focus my electrical problem investigation on my vehicles ECU. Much to my surprise I found 2 blown capacitors. Using the guide posted here I was able to order some replacement caps from digikey. I bought a couple of tools and got to work on the pcb. My capacitors emptied their contents onto approximately a US quarter sized area and left some rather nasty, dry, dark, crusty substance that was very well adhered to the board. I cleaned with alcohol, cotton swabs and a tooth brush but that stuff only came off in small patches. I used a small jewelers screw driver to gently scrape to remaining crust off of the board. I only used the weight of the tool, no excessive force. After scraping I noticed some gaps in at least 2 of the traces. A multimeter confirmed really high resistance on those traces. I'm looking for advice on how to repair those traces. They are very narrow and adjacent to each other. I have considered bypassing with wire but one of the traces ends with a "dot" that is basically the same width as the trace I don't know If I would be able to solder a wire to such a small point. I have several pictures and can upload later if you guys want to see what I'm talking about.

Thanks, -Z

Yamae

Without knowing what is your vehicle, I can't give you the detail but at least I can say is that other electrolytic capacitors on the board are also not in good conditions any more even if they are not leaked. One more thing I can say is that it may be a bit too late to fix judging from the situation. The leaked liquid tends to go inside the layer of the board and eats the copper trace there. If so, there is no way to fix the board.

ZionXIX

This is board comes from a 1996 Toyota 4runner SR5. I have posted some links to my dropbox so that you can view the photos at full resolution. At this point I dont have super amounts of hope for the board but i have decided to make a fun little project to work on in my spare time. Let me know if there are any problems with my links.

Thanks, -Z


Before capacitor removal
https://www.dropbox.com/s/2mvzpt7zoi...62522.jpg?dl=0


After capacitor removal, Before cleaning
https://www.dropbox.com/s/zh9lf7j3xm...74408.jpg?dl=0

After scrubbing with Alcohol and cotton swabs/ tooth brush
https://www.dropbox.com/s/zg4lrlcfjx...75140.jpg?dl=0

After scraping with small screwdriver
https://www.dropbox.com/s/5zup6oazg9...73551.jpg?dl=0

Here is the pin point in question that I am wondering if soldering a wire to it is even possible
https://www.dropbox.com/s/5je9iu4sy5...cated.jpg?dl=0

Yamae

If I were you, I would use wires 28AWG or thinner for signal lines to bypass every damaged trace soldering at both ends which shaped a small circle after polishing the surface. I would also check those are connected to the internal layer. This often needs a X-ray machine or an equivalent. For the power lines I would use thicker than 28AWG wires depending on the width of the trace. A 1.0 mm trace needs to use 26AWG or thicker.

ZionXIX

Hey thanks for the advice. Luckily the larger trace shows good continuity. I think its just 2 or 3 small traces that need attention. Im glad you mentioned a wire gauge because I was unsure which one to pick. It might be a while before post any progress. I live in the middle of nowhere and it takes like 2 weeks for anything to be shipped.

Thanks, -Z

jaaa

I finally managed to find an ECU from a pick/pull to work on the cap issue. Took just 15 minutes to go to LScowboyLS's first post and ordered(actually double ordered) the six caps I needed to replace all the caps on my 1996 lexus ls400. Took me a couple hours to replace the caps on the pick/pull one and installed it in my car. It may be a placebo effect, but I feel the car has more low end response with the new ECU. Took me around an hour to do the cap replacement on the second unit, since I had all the locations and set up to hold the boards in place. My only problem was my eyesight problem with close up work at the age of 67. I just may sell one of the ECUs or keep it as a spare. Anyway, thanks LScowboyLS for the links, it took almost no time at all to have the two sets of caps ordered and on the way. Total cost was around $13 and they arrived from snail mail in three days!

BTW, while I was at the pick/pull place, the lady at the check out station whispered to me that normally the workers in the back pull all the ECUs out of the cars for resale before they get to the public. She said they make a good amount of money by pulling them.

joytech22

Hi guys,

This is weird, my ECU has 9 caps on it but they're different to the 9 listed by oldskewel's post - for the record, my LS400 is a 95 year build, 96 plated.

These are the 9 caps mine requires - none on PCB 2:
2x 10uf 50v
2x 15uf 35v
2x 100uf 10v
2x 47uf 63v
1x 220uf 16v

This is in Australia, this model does not have an OBDII port and the ECU removal method was the same as the 98 models (along with like 3-4 other computers in the same space).

Our model engine power was also advertised with 204kw unlike most other countries with 194kw for the UCF20's.. My reason for replacing caps is:

• Tach/odo needles sometimes stay at 0 and suddenly work after a few seconds
• Brake light out dash indicator coming on randomly/Not detecting light out for a long time during driving
• Poor performance when engine is warm (replaced ECT sensor already)