All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor)
02-07-14, 01:52 PM
#706
Lexus Champion
Thread Starter
1998-2000 still has the defective PF (M) and PR (M) series caps, but the circuit is not near as hard on the caps and is more forgiving of some ripple, so this repair can be put off, however on 1990-1997 models, these capacitors are failing like crazy and causing a lot of headaches for LS400 owners, everything from running issues to shifting, not to mention that their leakage can catastrophically ruin your ECU to a point where it must be replaced rather than repaired, and then the replacement ECU will *still* need new capacitors. 
It sounds like you have gotten to yours early enough to prevent all of that.
And in saying your capacitors were fine, what was the ESR that you measured for each cap?
It sounds like you have gotten to yours early enough to prevent all of that.
And in saying your capacitors were fine, what was the ESR that you measured for each cap?
02-07-14, 03:31 PM
#707
I went ahead & replaced the 6 electrolytic caps on my 97 LS even though I don't have a problem with my ECU. My OEM caps are the brown ones. Once removed & inspected, they're in pristine condition & bone dried all around & underneath the caps. I've also measured each one w/ a capacitance meter & they're all within spec. Getting to the ECU & removing the caps are not a simple task so it's not a job for everyone. These are electrolytic caps so they're mainly used as by-pass caps which means their main function is to filter out ripple voltages from the DC lines (12 Vdc & 5.2 Vdc). Based on my result, if your cars are 97 or newer & run great without any known problem with the ECU, I strongly recommend you should leave them alone. This may go against LSCowboy's & Yamae's recommendations as they're great assets to our Lexus community but like the old saying: Why fix it when it ain't broken? Perhaps, Toyota has used new batches of caps for 97 & newer models so they're less prone to failure? You're the owner of your car so do what you think is best for it. I bought mine when it was a year old so it has been with the family for 16 years now & has just passed the 200K mark. It has been a great machine with practically zero defect.
02-07-14, 06:03 PM
#708
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BACKUP is always your good friend so you will still have a way back when something goes wrong. in my case, the ECU seemed running fine, I bought a replacement ECU off ebay for 50 bucks and use it on my car for a while to make sure it works properly. I then replace the caps on the old ECU.
02-07-14, 09:33 PM
#710
Moderator
02-07-14, 09:35 PM
#711
Lexus Champion
Thread Starter
I think it is too early for LS430 to have capacitor issues yet, and I don't know of any defective series of capacitors used in LS430, so I would say you're likely good for several years
02-08-14, 12:51 PM
#712
LScowboy- When I measured the old ones I took out, I used a capacitance meter so it measures capacitance values directly. I can use an LCR meter or an analyzer if you're interested in the equivalent series resistance (ESR) values but I think it's unnecessary. If the capacitance value hasn't changed then most likely the ESR shouldn't neither or vice versa.
To other folks- The manufacturer normally conformal coated the PWB (printed wiring board) on both sides with a polyurethane coating after all components were populated & tested to prevent FOD (foreign object debris) from shorting thus damaging the board so if & when you removed the electrolytic caps, do not mistaken the coating underneath the caps as leaking upon inspection. The coating is clear, gel like but should be dried. If it's wet then your caps are definitely leaking.
To other folks- The manufacturer normally conformal coated the PWB (printed wiring board) on both sides with a polyurethane coating after all components were populated & tested to prevent FOD (foreign object debris) from shorting thus damaging the board so if & when you removed the electrolytic caps, do not mistaken the coating underneath the caps as leaking upon inspection. The coating is clear, gel like but should be dried. If it's wet then your caps are definitely leaking.
02-17-14, 08:33 AM
#713
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I just replaced mine (thanks to LScowboy). I have 93 LS also. None appeared to be damaged on mine. However, I was going to replace all anyways for precautionary measure. In the process of replacing, I could not tell for sure, but I found one that appears to be just starting to leak.
Replacing caps were not hard as none of caps were surface mount type. With a little bit of practice, I think anyone can do this.
After the replacement, I am noticing few changes. I did not have any major problems with engine running or erratic trans problems but had sticking speedo/tech needle and had CEL & TRAC-OFF light with code 25 & 26, that just did not go away. Those problems seem to be gone. I will have to keep monitoring as they may reappear but it seems to be gone for now.
These caps will leak eventually as it has shown in this thread. If you have put an effort to remove the ECU, why don't you replace all 8 of them. It only cost me $6, including shipping cost.
Replacing caps were not hard as none of caps were surface mount type. With a little bit of practice, I think anyone can do this.
After the replacement, I am noticing few changes. I did not have any major problems with engine running or erratic trans problems but had sticking speedo/tech needle and had CEL & TRAC-OFF light with code 25 & 26, that just did not go away. Those problems seem to be gone. I will have to keep monitoring as they may reappear but it seems to be gone for now.
These caps will leak eventually as it has shown in this thread. If you have put an effort to remove the ECU, why don't you replace all 8 of them. It only cost me $6, including shipping cost.
02-17-14, 10:23 AM
#715
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Needle Sticking Problem
This not related to the caps on ECU but I don't think the sticking needle problem is related to caps on the instrument cluster. Caps on my instrument cluster have been replaced recently as well.
02-17-14, 02:47 PM
#716
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I am new here. I just replaced the capacitors on mom's 1991 LS-400 (she is original owner and it now has about 70000 miles). Anyway, ECM is Toyota PN 89661-50032 S/N is 175000-4110J. I had 2 caps left from above shopping list, a 10 uF and a 100 uF capacitor, i.e. only 9 on the 2 boards. No problem as they were cheap from Digikey.
I did not find any caps that were clearly leaking or failed as in the photos.
They were very hard to remove. I have replaced other components from PCBs before but never any as difficult as these. I probably averaged 30 minutes each to get them out. Also took my time figuring out which pins were the Capacitor from the back side of the CB (didn't want to undo wrong item). Solder would re-harden in time it took to remove soldering iron and get my solder sucker tool in place.
She has had problems with fast idle and car dies at lights sometimes and spent much money trying to get it fixed. I hope this works. She is 88 and it scares her when the car dies at stop lights even though it only happens once every few months (too often for anyone).
Thanks for the nice article.
I did not find any caps that were clearly leaking or failed as in the photos.
They were very hard to remove. I have replaced other components from PCBs before but never any as difficult as these. I probably averaged 30 minutes each to get them out. Also took my time figuring out which pins were the Capacitor from the back side of the CB (didn't want to undo wrong item). Solder would re-harden in time it took to remove soldering iron and get my solder sucker tool in place.
She has had problems with fast idle and car dies at lights sometimes and spent much money trying to get it fixed. I hope this works. She is 88 and it scares her when the car dies at stop lights even though it only happens once every few months (too often for anyone).
Thanks for the nice article.
02-17-14, 06:43 PM
#717
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Hello
This is my second post with the same problem found again, in another ecu of course because the one I repaired as this thread is working perfect!
Here pics of what I found:
Oohh well, I ordered new caps again.. but you know what.. this ecu is from a honda civic 92!!!
It was giving problems with fuel pump activation and engine idling and after caps replacement all problems dissappear!!!
Thank you again guys!!
This is my second post with the same problem found again, in another ecu of course because the one I repaired as this thread is working perfect!
Here pics of what I found:
Oohh well, I ordered new caps again.. but you know what.. this ecu is from a honda civic 92!!!
It was giving problems with fuel pump activation and engine idling and after caps replacement all problems dissappear!!!
Thank you again guys!!
02-18-14, 05:59 PM
#719
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02-20-14, 10:08 PM
#720
Lead Lap
with the help of Cowboy got the caps replaced. Havetn driven the car yet. however first thing-my climate control started working normally agian. not long ago it started to freak out on auto setting and blast the fans no matter what at strong heat.
Also changed the transmission mount and no more sinusoidal vibration at 1500 rpm free rev.
Doid the ecu first then mount to determine their individual effects.
Also changed the transmission mount and no more sinusoidal vibration at 1500 rpm free rev.
Doid the ecu first then mount to determine their individual effects.