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Crazy OEM nut.
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Discussion Starter · #1 · (Edited)
Has your MR2 been idling rough or unevenly? Is it hard to start first thing in the morning? When you come to a stop does the idle dip down a little too far and then come back up? Is the car dying entirely randomly, but then you can fire it right back up? If you said yes to any of those, you might have a capacitor going out in the ECU.

This is meant to serve as a "how to" guide for inspecting and replacing one or all of the capacitors in your ECU. This was done on a 93 SARD ECU (Japanese modified ECU), but the procedure is identical for any 93 JDM ECU, 93-95 US-spec ECU, and should be similar for any other 3sgte, 3sge, or 5sfe ECU.

First things first. A thank you to the guys over at Club Lexus for sorting this out for their cars. READ the entire first post in the link below. USE their links when it comes time to order your new capacitors.

http://www.clublexus.com/forums/ls4...exus-issues-solved-ecu-leaking-capacitor.html

And another thank you to a local member, James Blumenfeld for taking time out of his weekend to use his expertise to do this and show me how to do it properly.

So let's get to it!

First remove the ECU:

First pull the ECU fuse found in the fuse box located in the engine bay. Then remove the carpeting and fiber board on the engine facing side of the inside of the trunk. You'll see the ECU on the left. Use a 10mm socket to remove the three bolts holding it to the firewall.



Then remove the three grey connectors at the bottom of the ECU.



Lastly completely remove the white connector that's attached to the side of the ECU.



Your ECU should now be free to lift out of the trunk. Take the ECU to a well lit space you can work on and start with removing the top panel (should have the part number label on it), by removing the four screws, one at each corner, then do the same on the rear. Once you've lifted that off, you have another for screws to remove inside the ECU, shown here.



You can now fold the top board up and over to expose the entirety of the top and bottom boards.



On the 93 JDM and 93-95 US-spec 3sgte ECUs there are 8 capacitors in total. I'll highlight where all 8 are, and what capacitors you'll need, but only show one (idle control capacitor) being replaced. The procedure for all 8 is the same. Each of the 8 capacitor locations are marked here.



On the board, at the base of each capacitor is an etched in ID starting with a "C". Use the below list to identify what capacitor you need to use as a replacement.

C002 = 63v 47uF
C004 = 35v 33uF
C101 = 10v 100uF
C109 = 10v 220uF
C500 = 10v 100uF
C512 = 50v 10uF
C801 = 35v 15uF
C810 = 50v 10uF

We'll focus on C810, the idle control capacitor. Seen here, you can see it has already leaked out some. If you do not remove them and clean the board, they will eventually damage the board beyond repair.



To remove the capicitor, start from the back of each board, locate the leads for the capacitor, and using a soldering iron, release the capacitor from the board. Then use the soldering iron and a solder sucker to clean out the holes on the board. Then use a solution similar to the mentioned on the Club Lexus page, or a board cleaner from your locale electronics sore, to clean the board as best you can and remove any residue from the leaking capacitor. You can see here, that even after cleaning there remains some etching and discoloration of the board.



Now insert the new capacitor with the negative lead facing down, toward the connector end of the board/ECU (each negative terminal on the board is also marked with a "-"). Gently solder the leads to the board on the back side. Clip any extra leads sticking out and inspect your work. Make sure he solder is not touching any neighboring traces (copper lines on the board) or any other neighboring solder. If it is, use an exacto knife to separate them and clean things up.

You new capacitor should now securely be in place. Inspect all of your work, and recheck that you have the right capacitor values in the correct place.



Now reverse order to put everything back together and back into the car. (Don't forget to put the ECU fuse back in place!)

Then put the key in and turn it to the "ON" position for a few seconds. (~5 seconds) Then start the car. If it starts and everything is running smoothly, job done. Go for a drive to celebrate. If it does not, then recheck your steps and make sure either board in your ECU isn't too far gone from damage done by a leaking capacitor(s).
 

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You'll notice Nate's upper board has a daughter board" attached to it and the large integrated circuit could protrude down such that the replacement capacitor may need to be slightly relocated.
To gain access to the main board you'll neeed to remove the back cover as well - 4 phillips screws (actually they're JIS screws - with a little dot to mark them - which are slightly different from phillips screws but as long as you don't have to use excess force you'll be OK).

We had to mount one cap at an angle and another we used most of the lead length to move it off to the side about 3/4".
I put some teflon tubing over the exposed leads (you could just use some insulation from a piece of ~20 gauge wire as well).

Helpful hint - the longer lead on the caps is always the positive lead.
I used a low power solder station with a very fine tip. Sometimes the OEM solder is tough to melt so I melt a little bit of "regular" solder in the joint to get some flow in there.

Then on the relocated (or laydown) caps I put a little silicon sealent to hold it in place during those high G-force maneuvers.
It's best to use "low odor" silicon since it is far less corrosive.

Once the snow starts falling I'll be recapping my 5SFE ECU - and I'll post pictures.
 

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Awesome. Should be sticky.
 

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Ive got a Gen3 ECU that has intermittent issues I swear has to have this problem, but no capacitor leakage that I could see.

Since Ive already written it off and I dont need it, maybe Ill just proactively replace all of the capacitors and see if it dont fix it.

Having a spare ECU can come in handy. These things are only gonna keep getting harder to find.

If that works, maybe Ill nut up and proactively replace the caps on my IMEC sports ECU.
 

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Crazy OEM nut.
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Discussion Starter · #5 ·
Ive got a Gen3 ECU that has intermittent issues I swear has to have this problem, but no capacitor leakage that I could see.

Since Ive already written it off and I dont need it, maybe Ill just proactively replace all of the capacitors and see if it dont fix it.

Having a spare ECU can come in handy. These things are only gonna keep getting harder to find.

If that works, maybe Ill nut up and proactively replace the caps on my IMEC sports ECU.
It doesn't have to be fully blown out to be out of spec. Some of the ones we pulled appeared fine, but had just the tiniest amount of leak that you couldn't see with them in place.
 

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Ive got a Gen3 ECU that has intermittent issues I swear has to have this problem, but no capacitor leakage that I could see.

Since Ive already written it off and I dont need it, maybe Ill just proactively replace all of the capacitors and see if it dont fix it.

Having a spare ECU can come in handy. These things are only gonna keep getting harder to find.

If that works, maybe Ill nut up and proactively replace the caps on my IMEC sports ECU.
Most caps lose pretty much all capacitance after 10 years anyway. So almost everyone's ECU could use new caps.
 

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I need to get me one of those!
 

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Bumping this back up. Anyone know of anyone in the Los Angeles are that could perform these replacements? Or any place else? I've emailed taninautoelectronix.com, they do Lexus ECUs for $154, but I haven't received any kind of response.
 

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This is an old thread, but valid.

Heres a link to my thread. Its funny, I talked about doing it back in 2014, but never did. now I need to cause mine are bad.

http://www.mr2oc.com/61-3sgte-turbo/658722-gen3-engine-loss-power-cel-2.html

This is a thing guys. It really seems like the revision 1 ECUs were way beefier. Rev2 and Gen3 ECUs seem to be dying rapidly lately (a lot of them already have).
 

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I recently had the same issue, pulled my ECU and capacitors were to blame.

I will be updating the JDM ECU i just received when I get the capacitors in.
 

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I just recently replaced the idle capacitor on my ecu and it has improved my symptoms. I have leakage around the blue resistors that are right next to the idle capacitor in the picture. The resistors are TPC and VSV. I ordered replacements and they do not look the same. My question is, can someone identify what type and spec of resistor I need to order to replace them?
 

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I'm pretty sure you can verify this by setting your meter to test for resistance only when the resistor is isolated from the circuit board of course
 

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ECU capacitor replacement "how to" guide

Please post photos of the old and new resistors.
It would be unusual for the resistors (unlike the capacitors) to go bad unless an adjacent cap leaked and the fluid corroded the resistor leads. It's possible that you're confusing leakage for solder flux.
It's not unusual for the replacement resistors to look different - there are many manufacturers and appearances will vary.
Pictures!
 

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Resistors usually only fail from heat damage. This would be consequent to a different failure. For example, if another component shorts, then a resistor assigned to limiting the current in the circuit can overheat. Look for scorching or cracking, and also for heat damage to the board underneath. Ignore the brown deposits of rosin flux around the solder joints.

Carbon composition resistors, the ones with the brown phenolic bodies, are also somewhat unstable. Over decades, they can drift out of spec without showing outward signs of damage.
 

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Please post photos of the old and new resistors.
It would be unusual for the resistors (unlike the capacitors) to go bad unless an adjacent cap leaked and the fluid corroded the resistor leads. It's possible that you're confusing leakage for solder flux.
It's not unusual for the replacement resistors to look different - there are many manufacturers and appearances will vary.
Pictures!
I don't have pics since I've replaced the cap already and cleaned up the corrosion around the cap and resistors. I'm certain it's corrosion because it was bluish, just like the leakage around the cap. If you look at the last pic above, you'll see the blue resistors to the left of the cap. There was leakage on the bottom of the cap, and on both ends of the two resistors next to that cap. I believe they're labeled 2r2j or something like that.
 
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