All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor)
CL Community Team
Joined: Aug 2011
Posts: 4,172
Likes: 1,006
From: Japan
I must add some. In the past, I have fixed different ECUs and what I can say is that you have to be very careful for selecting the electrolytic capacitors. The internal impedance or the ESR is the key to select. The capacitance value was not very strict. Sometimes +200% did not cause any problem. For an example, I have used 100uF instead of 47uF and it was fully OK. But when I have used a regular type of capacitor, it did not fix some problem.
Those who could not succeed or who are about to fix the ECU, I suggest you to use low ESR type capacitors such as Rubycon type ZLH, Nippon Chemicon KZH, Panasonic EEU and other equivalents.
Those who could not succeed or who are about to fix the ECU, I suggest you to use low ESR type capacitors such as Rubycon type ZLH, Nippon Chemicon KZH, Panasonic EEU and other equivalents.
Last edited by Yamae; Sep 24, 2012 at 04:11 PM.
Thread Starter
Lexus Champion
Joined: Dec 2011
Posts: 4,078
Likes: 87
From: Birmingham, AL
ok so there's 4 different capacitors with 4 different voltages? I ordered a set of 10 pieces of rubycon zlh 1000uf 25v, what others do i need?
1995-97 LS400 needs 6 caps as follows:
Qty. 2 of 10uF - 50v
Qty. 1 of 47uF - 63v
Qty. 2 of 100uF - 10v
Qty. 1 of 220uF - 25v
not sure what you need the 1000uF caps for? - who told you to purchase that size?
Lead Lap
Joined: Jan 2007
Posts: 683
Likes: 3
From: UK
Sorry technical question, were the original capacitors in the ECU rated at 85 or 105 degrees?
Are the affected capacitors coupling or decoupling?
I assume as the capacitors age their ESR increases and capacitance decreases which in turn produces more heat and the cycle continues until the heat causes the plug to push out of the base and the electrolyte then leaks from the capacitor.
I normally use a product called 'Safewash" which is a water based foaming PCB cleaner that does not leave any residue then use the iso alcohol drying off with a hair dryer.
Thankfully I still have supplies of lead solder and don't have to use the leadfree substitute which is rubbish.
Are the affected capacitors coupling or decoupling?
I assume as the capacitors age their ESR increases and capacitance decreases which in turn produces more heat and the cycle continues until the heat causes the plug to push out of the base and the electrolyte then leaks from the capacitor.
I normally use a product called 'Safewash" which is a water based foaming PCB cleaner that does not leave any residue then use the iso alcohol drying off with a hair dryer.
Thankfully I still have supplies of lead solder and don't have to use the leadfree substitute which is rubbish.
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Thread Starter
Lexus Champion
Joined: Dec 2011
Posts: 4,078
Likes: 87
From: Birmingham, AL
the original capacitors are 105C, but far more important than temp rating is that the replacement caps are LOW ESR type!
I recommend 63/37 leaded solder for this job, and the safewash is fine but not necessary, vinegar and a soft toothbrush will clean the board safely as long as you follow that with a distilled water wash and then a couple of 91% iso-propyl alcohol washes
make sure you use one of the big Japaense cap brands - Rubycon type ZLH, Nippon Chemicon KZH, Panasonic EEU or Nichicon low ESR
inspect your work with a loupe afterwards
should be 6 or 7 caps depending on your model year, higher voltage caps than original are not necessary, but fine to use!
BE CAREFUL with the 4 ribbon cables that attach the two mainboards
ALSO - keep in mind that the capacitors do not have to be visibly leaking to be bad, therefore you want to replace ALL of them, even if they look fine!
I recommend 63/37 leaded solder for this job, and the safewash is fine but not necessary, vinegar and a soft toothbrush will clean the board safely as long as you follow that with a distilled water wash and then a couple of 91% iso-propyl alcohol washes
make sure you use one of the big Japaense cap brands - Rubycon type ZLH, Nippon Chemicon KZH, Panasonic EEU or Nichicon low ESR
inspect your work with a loupe afterwards
should be 6 or 7 caps depending on your model year, higher voltage caps than original are not necessary, but fine to use!
BE CAREFUL with the 4 ribbon cables that attach the two mainboards
ALSO - keep in mind that the capacitors do not have to be visibly leaking to be bad, therefore you want to replace ALL of them, even if they look fine!
Last edited by LScowboyLS; Oct 18, 2012 at 07:59 AM.
Driver School Candidate
Joined: Mar 2012
Posts: 31
Likes: 0
From: Michigan
I would like to order them before taking apart ecu, and do it in one go. I plan to do the dash capacitors at the same time - does anyone know their part numbers?
Thank you!
Thread Starter
Lexus Champion
Joined: Dec 2011
Posts: 4,078
Likes: 87
From: Birmingham, AL
here is the list of caps for 98-2000 models:
Qty. 2 of 10μF/50V
Qty. 2 of 47μF/63V
Qty. 2 of 100μF/10V
Qty. 1 of 220μF/16V
Qty. 1 of 33μF/35V
Qty. 1 of 47μF/25V
Qty. 1 of 330μF/35V
I am still working up a list of capacitors for the 1990-94 models
Qty. 2 of 10μF/50V
Qty. 2 of 47μF/63V
Qty. 2 of 100μF/10V
Qty. 1 of 220μF/16V
Qty. 1 of 33μF/35V
Qty. 1 of 47μF/25V
Qty. 1 of 330μF/35V
I am still working up a list of capacitors for the 1990-94 models
Last edited by LScowboyLS; Oct 8, 2012 at 07:13 AM.
Thread Starter
Lexus Champion
Joined: Dec 2011
Posts: 4,078
Likes: 87
From: Birmingham, AL
please remember, when servicing the ECU caps, these 4 critical points:
1. replace ALL of the electrolytic capacitors, even the ones that appear to be fine, they don't have to be obviously leaking to be bad - there are typically only 6 or 7 in total - the 98-00 models have 10.
2. make sure the caps you use are LOW ESR type and 105C rated and voltage is at least the original rating.
3. stick with high end Japanese caps - Rubycon, Nippon Chemicon, Panasonic, Nichicon.
Attachment 501425Attachment 501695Attachment 501426Attachment 501427Attachment 501695Attachment 501428Attachment 501695Attachment 501429
4. be very careful with the 4 ribbon cables that attach the two mainboards, if one of these comes partially loose then you have created yourself a lot more work.
1. replace ALL of the electrolytic capacitors, even the ones that appear to be fine, they don't have to be obviously leaking to be bad - there are typically only 6 or 7 in total - the 98-00 models have 10.
2. make sure the caps you use are LOW ESR type and 105C rated and voltage is at least the original rating.
3. stick with high end Japanese caps - Rubycon, Nippon Chemicon, Panasonic, Nichicon.
Attachment 501425Attachment 501695Attachment 501426Attachment 501427Attachment 501695Attachment 501428Attachment 501695Attachment 501429
4. be very careful with the 4 ribbon cables that attach the two mainboards, if one of these comes partially loose then you have created yourself a lot more work.
Last edited by LScowboyLS; Oct 21, 2012 at 11:04 AM.
Rookie
Joined: Oct 2012
Posts: 51
Likes: 1
From: Virginia
Model: 94 LS400
So i dont assume right now the 6 caps that are needed for 95 and up ordered from nippon, etc would be enough to order until the write up is done? i would like to do the dash and ECU at the same time again thanks for the help everyone.
Qty. 2 of 10uF - 50v
Qty. 1 of 47uF - 63v
Qty. 2 of 100uF - 10v
Qty. 1 of 220uF - 25v
So i dont assume right now the 6 caps that are needed for 95 and up ordered from nippon, etc would be enough to order until the write up is done? i would like to do the dash and ECU at the same time again thanks for the help everyone.
Qty. 2 of 10uF - 50v
Qty. 1 of 47uF - 63v
Qty. 2 of 100uF - 10v
Qty. 1 of 220uF - 25v