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All my crazy Lexus issues SOLVED!! (ECU-leaking capacitor)

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Old Sep 14, 2025 | 10:51 PM
  #1981  
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I just did the repair on my two 3S-GTE ECUs today. Took me a bit longer without a solder sucker but overall wasn’t too bad. I replaced with Panasonic FC series — these capacitors are just bulk decoupling caps for the 12V rail inside the ECU and the regulated supplies for the MCUs/etc, so I wasn’t too worried about ESR. I dug up the original datasheets for all of the stock capacitors and verified the new caps met or exceeded performance of the original parts.

For a 3S-GTE (I’ll look up the part numbers of ECUs later here, but from a 1995 SW20 MR2 and a 1997 ST205 GT-Four).
  • C105
    • Original: 220 uF, 10 V, Nichicon KM.
    • New: 270 uF, 16 V, Panasonic EEU-FC1C221
  • C002
    • Original: 47 uF, 63 V, UCC SXE
    • New: 100 uF, 63 V, Panasonic EEU-FC1J101B
  • C004
    • Original: 33 uF, 25 V, Panasonic NHE (aka GE)
    • New: 56 uF, 35 V, Panasonic EEU-FC1V560
  • C101, C894
    • Original: 100 uF, 10 V, Panasonic NHE (aka GE series)
    • New: 100 uF, 16 V, Panasonic EEU-FC1C101
  • C816
    • Original: 10 uF, 50 V, Nichicon PF
    • New: 15 uF, 50 V, Panasonic EEU-FC1H150
  • C823
    • Original: 15 uF, 35 V, Panasonic NHE (aka GE series)
    • New: 27 uF, 35 V, Panasonic EEA-FC1V270
  • C895
    • Original: 10 uF, 50 V, Nichicon PF
    • New: 15 uF, 50 V, Panasonic EEU-FC1H150

Minor diffs in lead diameter and height, but no fitment issues observed. All should be available Digi-Key, Mouser, etc.
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Old Sep 14, 2025 | 11:02 PM
  #1982  
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I didn't know what era of 3S-GTE has capacitor problems.
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Old Sep 14, 2025 | 11:07 PM
  #1983  
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Originally Posted by LeX2K
I didn't know what era of 3S-GTE has capacitor problems.
I think any Denso ECU from the 90s could be affected as similar core design / similar vintage of caps that were QATS based. S, JZ, UZ, etc ECUs seem to all be the same basic design, differing only in numbers of cylinders / etc and then the ROMs with specific fuel maps / logic.

I have a JZZ30 as well that I need to examine. Most of these are so low mileage that I’d guess the relatively low time spent biased may have prevented any leakage from occurring. One or two of the caps did spill as I desoldered, I blame the heat more as I wasn’t gentle, but perhaps they were close to it.
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Old Sep 14, 2025 | 11:15 PM
  #1984  
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Caps shouldn't puke their guts just from soldering. I don't attempt to solder suck the board I cut the leads off then pull them out, after that clean up with MG Chemicals solder wick. Safest method at least for me.
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Old Sep 15, 2025 | 08:44 AM
  #1985  
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Originally Posted by LeX2K
Caps shouldn't puke their guts just from soldering. I don't attempt to solder suck the board I cut the leads off then pull them out, after that clean up with MG Chemicals solder wick. Safest method at least for me.
That's what I tried to do, but had a few holes where I couldn't quite wick all the solder out. Judging from some of the caps, I don't think they thermally relieved the. negative/GND pads from the planes / polygons, which made things annoying.

Brought the boards into work today to scrub / wash off the flux so I'll take some close-out pics and post them here.
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Old Jan 5, 2026 | 12:45 PM
  #1986  
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[QUOTE=Yamae;11795784]

1, LScowboyLS had gone about a decade ago and never came back.

I wanted to reach out on here to let people know I've made contact with him via Facebook (Japanese ECU ECM PCU Repair by Lscowboyls) and had my ECU repaired successfully in my 97 Celica just recently. Response time was really good and turn around on the repair upon receiving ECU was good.
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Old Jan 13, 2026 | 09:37 AM
  #1987  
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Originally Posted by as99east
Try:

Relentless Motorsports

Tanin Auto Electronix

Jim Walker aka “The Lexpert” - he rebuilt mine. TheLexpert@gmail.com

Note that since you have an ECU that someone has already monkeyed with rather than the factory original, that may affect the warranty they will be willing to offer. Worth confirming that up front. Good luck!
Reporting another repaired ECU. I had Tanin Auto Electronix do the repair (along with the gauge cluster). I have opened up a couple of laptops/phones but am not doing that and/or soldering consistently enough to be confident in doing the repair correctly.

I wasn't experiencing any ECU-specific problems, but figured I would have it done preventatively since my speedometer and tachometer were intermittently working.
The car has around 171k miles, with about 3k of them under my ownership over the past 10 months or so.

Thankfully my ECU still had factory seals, so the warranty given by Tanin was 1 year (if you don't break the new seals they install).

Here's the video I made about it -
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Old Apr 22, 2026 | 08:55 PM
  #1988  
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Originally Posted by Yamae
---

Question, is there any way the ECU capacitor issue can cause a car to not start only when its warmed up?
its an extremely specific and constant re-occuring issue. car starts fine when cold/cooled down, but when its at operating temp, it will not restart, only the relay clicks rapidly.

car itself has new starter, coils, plugs, wires, timing belt job, fuel pump and fuel filter, replaced starter relay, battery new, car does run and drive fine, it did have a slight rough idle after all the new stuff was replaced, however i did also replace the coolant temp sensor (the 2 wire one that sends readings to the ECU) and the car does run better now...but the starting issue remains....replaced it thinking that one communicates to the ecu and prevents the starter from engaging....but, it was not successful in that.

the starting issue was going on before all the new parts....so nothing new or any work done has solved this problem.....

however, on a long drive, my cluster was flipping out (which this car has never done before), lights going blank and such flickering all over the place and when the backlights went out warning lighs appeared, and the when lights came back warning lights went away...and felt a random very slight cut out after 30 min of highway driving...i did remove the ECU and opened it, and found only one capacitor small leak that was along the fuel injection lines of the board which explains the weird cutting out driving experience...but the rest of the board is clean...
while yes another capacitor can be the issue without a leak as detailed in this sticky thread, is there any chance another capacitor being weak causing these cars to not start under this specific condition?

i know the ECU needs to be redone because of the other capacitor, but before i spend the money i want to fix this weird no start issue, or confirm that the ECU can actually cause this otherwise ill just be dumping more money into this car and all for nothing.

.

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Old Apr 23, 2026 | 06:42 AM
  #1989  
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Have you read this at the post #1?
● random not starting or cutting out.

QAS capacitors seldom last for 30 years and it is the often case that copper traces are damaged.
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Old Apr 23, 2026 | 07:52 AM
  #1990  
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Originally Posted by Yamae
Have you read this at the post #1?
● random not starting or cutting out.

QAS capacitors seldom last for 30 years and it is the often case that copper traces are damaged.
yes i did read that. but RANDOM not starting....my issue is it always starts when its cold/cooled down, but never starting when its hot. which is where im not seeing it as a random issue. is one of the capacitors connected directly to a temp related starting issue somehow?
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Old Apr 27, 2026 | 04:06 PM
  #1991  
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Originally Posted by sigtwenty
Question, is there any way the ECU capacitor issue can cause a car to not start only when its warmed up?
its an extremely specific and constant re-occuring issue. car starts fine when cold/cooled down, but when its at operating temp, it will not restart, only the relay clicks rapidly.

car itself has new starter, coils, plugs, wires, timing belt job, fuel pump and fuel filter, replaced starter relay, battery new, car does run and drive fine, it did have a slight rough idle after all the new stuff was replaced, however i did also replace the coolant temp sensor (the 2 wire one that sends readings to the ECU) and the car does run better now...but the starting issue remains....replaced it thinking that one communicates to the ecu and prevents the starter from engaging....but, it was not successful in that.

the starting issue was going on before all the new parts....so nothing new or any work done has solved this problem.....

however, on a long drive, my cluster was flipping out (which this car has never done before), lights going blank and such flickering all over the place and when the backlights went out warning lighs appeared, and the when lights came back warning lights went away...and felt a random very slight cut out after 30 min of highway driving...i did remove the ECU and opened it, and found only one capacitor small leak that was along the fuel injection lines of the board which explains the weird cutting out driving experience...but the rest of the board is clean...
while yes another capacitor can be the issue without a leak as detailed in this sticky thread, is there any chance another capacitor being weak causing these cars to not start under this specific condition?

i know the ECU needs to be redone because of the other capacitor, but before i spend the money i want to fix this weird no start issue, or confirm that the ECU can actually cause this otherwise ill just be dumping more money into this car and all for nothing.

.

Most likely it is the starter itself. I have had this exact same issue on my 93 LS400. It was the contacts in the starter. Cheap to replace but a lil bit of a PITA as the starter is under the intake manifold.

https://www.ebay.com/itm/40496614414...IaAlZYEALw_wcB
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Old Apr 27, 2026 | 04:08 PM
  #1992  
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Originally Posted by williamb82
Most likely it is the starter itself. I have had this exact same issue on my 93 LS400. It was the contacts in the starter. Cheap to replace but a lil bit of a PITA as the starter is under the intake manifold.

https://www.ebay.com/itm/40496614414...IaAlZYEALw_wcB
starter is brand new, and old starter did the same thing....which is why i did a new starter to begin with.
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