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.

 

ordered the capacitors today $10 10 pieces rubycon zlh
Thanks for the info

 

where did you get all six (4 different capacities & voltages) for only $10?

 

could changing these help if i have a power drain from somewhere? if the car sits for 2 days its completely dead. brand new alternator and battery.

 

**** 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?

 

which caps you need and how many depends on the year model of your LS400

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?

 

I cancelled the order I have a 91, there's actually a store in San Diego I can walk in and buy them called *****'s Electronics.

 

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.

 

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!

 

Thanks for the write up on this matter. Seems to happen a lot on the LS400's and not so much on the SC's. It does happen but it seems more often on the LS's..

 

Does anyone know off hand what capacitors I need for a 1993 Lexus LS400?

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!

 

+1 I would vote that this be added to the FAQ sticky. Maybe someone would be kind enough to break down how many, which type, and recommended brands to be saved in the first post.

 

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

 

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.

 

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