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My intention is just extend the life of our LS400/Celsior not to affect the global electronics supply chain.
But in the past I have strongly experienced that my little work has affected a lot to parts manufacturing companies and the market situations. I had to be careful what I designed.
The other day, a director at the local Toyota dealer said, "Many old cars we have sold are still running around here and we cannot sell new cars well".
I said, "It may be because you have been doing good repair jobs".
He said,"We used to do the ECU replacing jobs but almost none these days. Old cars are still running many and I just wonder why?".
I don't think my assistances to local independent repair shops are affecting the dealer's business, but I just wonder why he said it to me.
This. This is AWESOME. Brought a smile to my face. Keep up the good work Yamae. My baby is running much better now thanks to the ECU fix.
My intention is just extend the life of our LS400/Celsior not to affect the global electronics supply chain.
But in the past I have strongly experienced that my little work has affected a lot to parts manufacturing companies and the market situations. I had to be careful what I designed.
The other day, a director at the local Toyota dealer said, "Many old cars we have sold are still running around here and we cannot sell new cars well".
I said, "It may be because you have been doing good repair jobs".
He said,"We used to do the ECU replacing jobs but almost none these days. Old cars are still running many and I just wonder why?".
I don't think my assistances to local independent repair shops are affecting the dealer's business, but I just wonder why he said it to me.
Toyota and the many behind the scenes in this model/time period did a job. Fixing these small bits has fantastic results in keeping these on the roads. Big thanks for your many contributions in keeping them road worthy.
i feel any car manufacturer has the capability to create the most reliable car ever, but refuses to since they would work themselves out of the market over time.
a wise engineer told me, anyone can design something to last forever, it's designing something to last only a selected number of years where the challenge lies. with this in mind, most car makes design to last only a few years before they want you to purchase another. it's the nature of the business to survive. offtopic, my apologies !
I have a 1995 Lexus ES300, could I have the same problem? I have the symptoms. What Capacitors should I use? Same ones?
ES300 series models were not sold in Japan. The model named Windom was an equivalent but only the body. The engine was different and I don't know much about ES300. But in the ECU, there must be electrolytic capacitors that contain quaternary ammonium salt since bigger engines required the less ripples for the processor's VCC line.
I did this repair on my '91 today. No problems, car seems to run fine now, but I guess it was not running too bad beforehand either. So I can't say it fixed everything, but it certainly did not make anything worse. We'll see if the engine code 25 comes back. I'll also be replacing O2 sensors (one done already) and the fuel filter just so I don't have to worry about those later.
EDIT - after a day, I can now tell there is an improvement. There were some minor glitches in shifting and idling that must have come in so gradually over the years that I did not notice them. I do now notice that they are all suddenly gone. Code 25 has still not returned. There were no significant visible signs of the caps leaking when I replaced them.
Post #1 right now calls for 11 capacitors for the 1991. I bought them all (several extras too) from Digi-key and searched and searched on the boards today but could only find 9 to replace. Post #1 currently says "1990-92 LS400 needs 10 or 11 caps as follows:"
Qty. 3 of 10μF - 50v - but I found only 2
Qty. 2 of 15μF - 35v
Qty. 3 of 47μF - 63v
Qty. 2 of 100μF - 10v - but I found only 1
Qty. 1 of 220μF - 16v
I found and replaced 2 on the left board and 7 on the right board. If anyone knows where the other two are hidden, please let me know. The 9 I found are all very obvious in the photos.
Some of the numbers on the label on the outside of my ECU are:
1750004110J
89661-50032
175000-4110 12V
1UZ-FE
0-467
As far as I know it is original and never opened before this.
EDIT - nice that I can still do this 6 years later. I will add that my 1991 does not have TRAC, no air suspension, no phone, IS a California car. ECU has been running solid since then.
Wow! Thanks for this. I'm having trouble with my display panel, windows/sunroof, and telescoping steering wheel. Do you think this could solve my problems?
Wow! Thanks for this. I'm having trouble with my display panel, windows/sunroof, and telescoping steering wheel. Do you think this could solve my problems?
The answer is No. The ECU doesn't control everything. None of them are related to the ECU discussed here. You should solve those separately. Search the forum and you will find most of those items.
But it is a good idea for you to replace those ECU capacitors since your car is not very young and different worn-out problems.
I did this repair on my '91 today. No problems, car seems to run fine now, but I guess it was not running too bad beforehand either. So I can't say it fixed everything, but it certainly did not make anything worse. We'll see if the engine code 25 comes back. I'll also be replacing O2 sensors (one done already) and the fuel filter just so I don't have to worry about those later.
Post #1 right now calls for 11 capacitors for the 1991. I bought them all (several extras too) from Digi-key and searched and searched on the boards today but could only find 9 to replace. Post #1 currently says "1990-92 LS400 needs 10 or 11 caps as follows:"
Qty. 3 of 10μF - 50v - but I found only 2
Qty. 2 of 15μF - 35v
Qty. 3 of 47μF - 63v
Qty. 2 of 100μF - 10v - but I found only 1
Qty. 1 of 220μF - 16v
I found and replaced 2 on the left board and 7 on the right board. If anyone knows where the other two are hidden, please let me know. The 9 I found are all very obvious in the photos.
Some of the numbers on the label on the outside of my ECU are:
1750004110J
89661-50032
175000-4110 12V
1UZ-FE
0-467
As far as I know it is original and never opened before this.
I'm glad to have this done.
1991 LS400 ECU, left board, 2 caps
1991 LS400 ECU, right board, 7 caps
Thanks for the report, oldskewel. So yours have 9 capacitors. There are some variations of the ECU depending on locations to ship.
I was able to, after changing the #1 speed sensor and transmission solenoids, fix my 1994 LS400, by switching out the dang ECM. Didn't wanna chance changing capacitors with my limited soldering experience and instead elected to get a rebuilt ECM from Auto Computer Exchange.
For anybody having same issue, error code 42 which is speed sensor #1, tranny not going into overdrive and no cruise control, you might wanna either try to change the ECM or do the caps thing as per this thread FIRST! I read later, after changing mine , if your speedometer works then it's highly likely that the speed sensor is not failing. Why it gives the 42 error code is beyond me, probably the caps things.
I opened up my ECM and it looks VERY CLEAN, not at all like the fotos posted by LScowboyLS. That's not to say the caps aren't toast or almost but no visible evidence but there's obviously something in the ECM that was acting up.
I'm relieved but now I just have to figure out how to put everything back together, I know I should've taken fotos! The schematic on the first page isn't quite how mine fit. Anybody got access to other model schematics???
I just replaced the capacitors on my 94 gs300 ECU. The factory capacitors all looked perfectly fine on the outside, but I suspect that they were causing some issues.
There were 9 capacitors in total (listed below). The soldering was a bit hard at first duen to using a 30 watt, cheapo soldering iron. I plan to install the ecu in the morning and I hope everything goes great the first try
2- 10uf
2-15uf
2-100uf
2-47uf
1-220uf
I also bought an excessive amount of capacitors and I have every size listed by the OP in my possession. I would be more than happy to help fellow members that may have a hard time sourcing them. Just pay for shipping that's all.
Great post.
i would greatly appreciate the caps, i have a lexus gs300 i bought 3 weeks ago. i change the transmission, fuel pump, router sparks plugs fuel filter. car still starts then shut off.
do you still have the extra capacitors. plz say yes
First of all, thanks to Yamae and LSCowboy for their contributions. I just replaced the 10 capacitors on my 91 LS400 and I can tell you where the capacitor you're missing is: Look in the lower left part of your board (the one with 7 caps) - there is an empty spot labelled "C413" about halfway between the center and lower left corner. My ECM is 89661-50041 and I have trac control. If your car doesn't have trac, it may explain the difference.
Btw, someone in post #469 also mentioned that they only had 9 capacitors.
Also, Yamae - is it important to put a protective coating over the areas that have been worked on?
Originally Posted by oldskewel
I did this repair on my '91 today. No problems, car seems to run fine now, but I guess it was not running too bad beforehand either. So I can't say it fixed everything, but it certainly did not make anything worse. We'll see if the engine code 25 comes back. I'll also be replacing O2 sensors (one done already) and the fuel filter just so I don't have to worry about those later.
EDIT - after a day, I can now tell there is an improvement. There were some minor glitches in shifting and idling that must have come in so gradually over the years that I did not notice them. I do now notice that they are all suddenly gone. Code 25 has still not returned. There were no significant visible signs of the caps leaking when I replaced them.
Post #1 right now calls for 11 capacitors for the 1991. I bought them all (several extras too) from Digi-key and searched and searched on the boards today but could only find 9 to replace. Post #1 currently says "1990-92 LS400 needs 10 or 11 caps as follows:"
Qty. 3 of 10μF - 50v - but I found only 2
Qty. 2 of 15μF - 35v
Qty. 3 of 47μF - 63v
Qty. 2 of 100μF - 10v - but I found only 1
Qty. 1 of 220μF - 16v
I found and replaced 2 on the left board and 7 on the right board. If anyone knows where the other two are hidden, please let me know. The 9 I found are all very obvious in the photos.
Some of the numbers on the label on the outside of my ECU are:
1750004110J
89661-50032
175000-4110 12V
1UZ-FE
0-467
As far as I know it is original and never opened before this.
09-18-14, 01:43 AM
I had to be careful what I designed.
job. 
Fixing these small bits has fantastic results in keeping these on the roads. Big thanks for your many contributions in keeping them road worthy. 
, if your speedometer works then it's highly likely that the speed sensor is not failing. Why it gives the 42 error code is beyond me, probably the caps things.
