I don't think that the 1st and the 2nd problems are related to ECU capacitors. Needles are mostly mechanical related and the brake light warning circuit is an independent circuit. The main ECU has nothing to do with it.

 

This is a fabulous thread! I have a 98 Avalon (build date 4/98) that I suspicion has a problem in the ECU. It is giving me two problems. This car has 145,000 miles and runs great. The check engine light is not on but it fails our emissions test because they say it is not resetting itself. Some tests show no communication and some show no codes when they do get communication. Our testing center says it shows that it is not resetting itself and so it fails. I've changed the battery out recently but it has been driven every way you could imagine and for many miles since the change. No check engine light ever except on the initial key turn (when all the lights come on).
Here is a problem that it has had for a couple of years. If you start the engine and then turn it off it will NOT restart unless you first take the key out of the ignition and put it back in. It will then fire right up. This is also how I get it to make communication with some OBD readers. It spins the engine fine but it will not fire unless the key is taken out and re-inserted.
I opened the ECU up and it looks great except for one cap which "may" be bulging. It appears the hermetic sealant on the board has tiny cracks right where you might expect a cap to pop.
In the pic below, it is the one at the top right side (47uf).
My real problem right now is that I would like to replace the caps but they are surface mounted and not the through hole type that are in the 1st page list. There are six caps, all the same value as those on the first page for the 98's only they are surface mount design. I need help ordering the right ones to replace them with. I do have experience in this type work but I want to make sure to use the best caps and I'm really leaning on you guys to help me with that. Please help me find these caps in the right package for my ECU.
I've searched this thread but I'm unable to find any info on surface mounted caps.
Also, if anyone thinks I should check something else please share your thoughts. Any help would be greatly appreciated!

 

I'd select the capacitors in the link below for the ECU. It is about the series Nichicon UCZ.
http://www.nichicon.co.jp/english/pr...pdfs/e-ucz.pdf

But I don't think you can fix your problem just changing capacitors. You need measuring equipments and skills to investigate the circuit. Things are not always simple, you know. The process I found the ECU capacitor problem on a Celsior is that I needed to analyse the circuit thoroughly and confirmed ripples at the regulated DC lines.

 

Thank you Yamae for your response! I was just shutting things down for the night. Work comes early for me in the morning but you give me hope and my rest will be much sweeter now!
I'll let you know what I find out. You're helping a lot of people and your time is appreciated much!

 

Do you know what kind of capacitors I need for my 1993 gs300

 

I recently purchased an ECU of the same part number as mine from ebay that had the caps replaced. I tossed it in the car and the car would crank but wouldn't start. I popped my old ECU back in and the car started fine with no problems. I had the battery disconnected between switching ECUs and once the new one was in, turned the key to ON and let the car sit like that for about a minute before trying to start it.

Just out of curiosity before I request for my money back, is there a procedure to be followed for putting in an ECU that wasn't originally in that car? Like some sort of flashing type of procedure?

 

What year? If you have an immobilizer, you need to get the ECU programmed to your keys in order to get spark/fuel.

 

It's a 94, it does have the factory alarm on it. Is there a rough estimate of how much it would cost?

 

As far as I know the gen 1 should all be a just install and go. I don't know the 93's and 94's though. There are some updates to them, but since they are NOT a CAN system there would be no reflashing a thing, especially if you have to jumper the data port to read the codes. So that alone says its plug and play. The only important thing is the ECU that you got needs to be one that has what your car has as far as the Trac option. If you have Trac you need a Trac ecu, if you don't, you need an ECU that is not Trac. If all that is cool then the ecu you got is toast. And what I think happened is its some wanta be ECU tech that doesn't know a thing about ESD, and likely fried some circuits. Too many people are flippant about ESD, you see it on youtube all the time. I know all about it because I ruined a mother board for a pc one time by not being careful.

 

From what I've been reading, people were able to put a different ECU in their 93-94 without issues. I've also read that the different models ( 50140, 50141, 50142) are all compatible and a non-trac ecu will work in a trac car. I can't really vouch for this, but a couple of people have stated that it's fine in this thread:

https://www.clublexus.com/forums/ls-...numbers-2.html

I'm going to e-mail the seller and try to find out as much information about where this ECU came from, but from the looks of it, trying to get my money back is my best bet.

 

I think it was Yamae that posted a list of the ecu's and years and build dates they came in. You will not be using a 90 to 92 ecu in a 93 or 94 that I know of.
How can a non trac ecu work in a trac car?

 

I meant as in the different 93-94 models, they can be interchanged according to various other posters on the forum. I've also read that non-trac ECUs will work, but the traction light stays on and is inoperable. So the car runs, but doesn't have trac. This is all based off of what I read, is it true? who knows lol.

Anyway the seller is allowing me to return it for a refund, so that's a positive. I'm currently searching for an ECU that I don't have to pay an arm and a leg for, so if anyone has one please PM me.

I'm going to replace the CAPS in the one currently in my car, I would just like to have a spare one in case I damage mine.

 

Here's a tid bit of info that may help others.
I didn't replace my caps in mine. I don't think they were bad anyway. My problem as explained in earlier posts may be a different one.
I bought a used ECU from a salvaged wreck. Swapping out ECU's is no big deal but with the "immobilizer" system any other ECU is useless without the keys that originally matched it.
Reprogramming the "new" ECU to match your old keys is required on my 98 Avalon.
I found the eprom chip that stores that info and was able to swap the one from the original ecu onto the "new" one.
Worked like a charm but I don't think my original problem was cured leading me to believe my problem is elsewhere.
See my post, #1382, for a pic of the chip and its location. The eprom location is IC900, located at the lower right side in the pic above. Make certain to get the "polarity" correct when swapping. It will be marked with a small white line on the upper end of the chip.
My model is the only one I know about but I did see online where others had been done as well, sometimes requiring two chips be swapped.
I'm sure it could be done on any if the correct eprom can be located.
For the more experienced techie, this chip can actually be re-programmed using your computer if it has a serial port.
Search the net for how to do this. I may do my old one just for the fun of it. It'd be good to have a ready to go spare on hand.

 

So Ive had to put a hold on repairing my ECU. Every trace I bypass seems to have no effect despite passing continuity tests. I replaced all but 1 capacitor. I finally had to order a replacement used ECU and that fixed my problems. I would like to keep working on the old ECU and get it working as a backup and to practice my soldering skills. The thing currently holding me back is the lack of a board diagram since its a multilayered board. I think there may damage I cannot see. I have email Toyota customer service asking for a diagram. I doubt I will get it but its worth a shot.

-Z

 

I know they show it on some youtube videos, using a dmm to check continuity on a pcb. Personally I would not recommend it because if the dmm uses a 9volt battery it could damage IC's. I'd like to hear from Yamae on this one. It doesn't take much over voltage to punch through the very small barriers in micro miniature electronic components.