Yamae

Oh, Yes. That's what happened here in Japan a lot. Most of owners who's car was not young and some strange problems are there, he or she wanted to use a used ECU picked up at junk yards to save money. I seldom have seen a person who was successful doing that.

Most of them were spending extra money for many parts as well as the ECU. The shop owner asked me to help and I found electrolytic capacitors were not holding enough capacitance as well as the ESR was increased.

Replacing them to low ESR electrolytic capacitors fixed the problems next to next. That was the beginning of the story.

A little later on, I found several owners here at Club Lexus having the same problem and I suggested them to replace those capacitors. There were no quick responses but all of the sudden you Cowboy replied me.

I'd say most of junk yard LS400 except collision cars were sent there because poor mechanics could not fix the problem. Those deteriorated capacitors may be beyond their understandings. Modern cars are equipped with many electronics devices but many of mechanics are not very familiar to those. Also many car owners are the same. Someone like you can help many people, Cowboy. If I were fluent enough in English, I also could help them more.

CaptainN

Pulled out the ECU, disassembled it, and found 3 brunt capacitors. sadly I didn't have the cam at that time. but will keep you posted once I get it fixed by evening!

hopefully the transmission problem get solved, and if not, at least I will be able to read the error code.

that explains everything, the car was stored for 2 years without moving! we'll see how it runs after it's fixed.

LScowboyLS

you must order the correct capacitors - the capacitors you have laying around or could purchase locally are not the correct type! - this repair takes a special brand and special rare type of Japanese capacitor in order to work! - there is also a huge problem of counterfeit capacitors on the market, this is why I provided the links to Digi-Key, the only authorized distributor of these 4 brands who stocks the correct special type.

please use the links to the correct capacitors in post #1 of our ECU capacitor thread

CaptainN

Capacitors where replaced with the Japanese one! made sure they're the correct order, the problem still persist! luckily there were another ECU in hands also suffered from brunt capacitors that were replaced with very same capacitors and WHAM!!! ALL PROBLEMS GONE!! it ran fine again!!

perhaps my ECU suffered from a short circuit???

Dranom

iTrader: (7)

Glad you got it sorted out!

peterls

As far as I know, capacitors go bad from not being used. They need to have some charge in them, to keep them healthy, otherwise once completely discharged, they go bad, the first time they are used again.
(and if I am wrong here, I am sure Yamae will correct me )

LScowboyLS

yes, vehicles that have sat a lot (like low mileage, snowbird-owned LS400's) are particularly afflicted with the ECU capacitor issues, though it eventually affects all LS400 models, as Yamae advises, though 98 and later have a better tolerance for it, so 98-00 models will be affected in the future more than today

Yamae

Yes, you are mostly right. The complete discharge is not a problem but the disuse for a long period of time causes problems.

You can find the detail at the middle part of http://en.wikipedia.org/wiki/Capacitor.

I just picked up the related part from there.
Electrolytic failure from disuse
Electrolytic capacitors are conditioned when manufactured by applying a voltage sufficient to initiate the proper internal chemical state. This state is maintained by regular use of the equipment. If a system using electrolytic capacitors is unused for a long period of time it can lose its conditioning, and will generally fail with a short circuit when next operated, permanently damaging the capacitor. To prevent this in tube equipment, the voltage can be slowly brought up using a variable transformer (variac) on the mains, over a twenty or thirty minute interval. Transistor equipment is more problematic as such equipment may be sensitive to low voltage ("brownout") conditions, with excessive currents due to improper bias in some circuits.