surfRider

I hope this helps someone else as this did not even cross my mind until Yamae mentioned it to me in another thread. I was concerned that one of my replacement caps was not getting contact at the - lead (clearly marked on the board). Yamae mentioned that that is a ground. I did feel a little foolish as I have not messed with capacitors for some years, pretty basic. Upon checking the negative leads to ground for all of the replaced capacitors I found not only was the 47 uf not good but also one of the 15 uf. If I cannot correct the connection I can make a couple of jumper leads to ground for both of these. I thought someone else could use this simple test to check out their solder connections after cap replacement.

seattleted

Thanks so much for this amazing thread! I'm having very similar issues in my 1999 GS300. It started when on the road to visit my Dad in very rural Eastern Oregon. Car cut out, sputtering to a finish luckily off an exit where I luckily still had service. Towed into town at night and the next morning car started up no problem. But 400 miles from home and sounding very much like a fuel pump, I replaced the fuel pump. Figured out on the way home it wasn't the fuel pump. Car went into limp, RPM's not going above 2k. Pulled into a rest area and approximately 1.5 hours later car started and I went for it. Much cooler at night I made it all the way home. My mechanic at home thought it must be the coils (which were having issues) so he replaced but upon start up ... hmmm still having trouble. Great guy he only charged me for parts for the coils. He tested MAF, isolated the intake etcetera. His idea is that it's the ECU. Then I came upon this thread. I am working on getting the ECU out to figure out what capacitors I will need then I will give the ECU to my mechanic for the (hopefully) fix.

Symptoms:
Barely starting, sputtering start then dying, lack of power, turn the key and nothing happens.

I will update with progress. Is anyone familiar with the GS300 ECU for capacitors?

Dinocards

I am heeding your warnings Sir.. Took out ECU inspected both boards... Looks new and no leakage..however it's gonna happen soon. Murphy's law. Haha

cribbj

I have a ’94 Supra with A/T (actually it’s now my son’s car), and it was experiencing the blown cap symptoms:

• Hard to start
• Both CEL and MIL were lit
• No A/C
• No power
• Running rich
• Occasional misfire
• No codes when E1 & TE1 were jumped in the diag connector

I pulled the ECU (89661-14510) and opened it up to see if I could visually confirm the problem, and immediately found 2-3 capacitors that had this brown/black fuzzy junk around their bases:



I took stock of the caps and their location, and then crossed them over from Cowboy’s table in Post 1:



Here are their locations:

Main Board (BTW, the gizmo to the right, covered in duct tape is an embedded Greddy BCC):



Daughter Board:



I clipped the old ones out, and found that they were all leaking:



Yuk:













Desoldered and pulled out the remaining leads, wicked up the excess solder & cleaned up the corrosion on the board. This one had me worried about the possible damage to the trace, but it cleaned up OK in the end:




I installed the new caps (neglected to take pics), put the ECU back in, and the car now runs like a raped ape again.

Thanks to Cowboy & Yamae for a great thread & fix!

RA40

iTrader: (6)

Congrats on the successful repair

Yamae

Thanks, cribbj, for the report with detailed photos and the capacitors list. I'm sure many Supra members will be helped by you.

I have a question, cribbj. You introduced us 7 symptoms. Which was the first symptom among those?

cribbj

Hello Yamae, I wish I could answer your question, but I can't - this is my son's car and it was displaying all these symptoms when he gave it to me to fix.

According to him, the car would not "run right" intermittently, and when it did this, it would be hard to start, it was difficult to keep running when cold, the idle would vary from 1200 to 1500 RPM, and the A/C would not work.

He neglected to mention the MIL and CEL, misfiring, and lack of power.

weinerface

Hey guys!

ok so first I HAVE to say, Lexus owners in forums are just the most amazingly competent people I have ever seen. I bought a 92 sc400 for $500. interior is s*** but that is of no concern to me. Ive never owned an import, and when i got it the power steering was shot, ran rough, brakes were shot, exhaust was just something aweful sounding. I lurked this forum and was able to "with ease" I might add, fix every single issue. your troubleshooting and guides are second to none. im so happy wth my SC now I cant even describe......

.then.....duh duh dum.....on my way home from a 100 mile round trip and the auto trans decides, hey! first gear sounds good while doing 70mph! no codes, no blinking OD light no CEL just no power and its reving at like 5k, I pulled over right away put it in park and shut the car off. tried checking codes (i keep a paperclip in my cupholder from when i bypassed my fuel pump ECU diagnostic port seems unresponsive and i cant get the OD light to blink at all (it stays on while i have the OD button pushed in just fine, but wont blink even just the 2 blink meaning ok) I barely had any signal on my phone, i found this thread right away though and begain suspecting the transmission ecu based on the symptoms in the thread, although what i could read was limited cause the page kept not loading all the way.

so i decided screw it, ive got a donor car, if i lunch the tranny then oh well hopefully thats all i break. (i was 50 miles from home in the desert, i dont like to walk) Started the car shofted into drive and away i went, all seemed fine, for about 10 miles, then same thing. pulled over, turned the car off turned it back on and tranny worked fine for another 5-10 miles. it did this the whole way home except for the last mile or so where i put it in OD and just drove it at 10mph home down side streets. (when it throws itself into 1st it stays in first and will drive just fine as long as im creeping at 1st gear speeds)

so far:
tried resettiing ECU by removing negative battery terminal for 20 minutes= same symptoms
tried driving in OD on and off= same symptoms
checked fluid= looks fine

only thing that fixes it temporarily is turning the car off and on again, as soon as i start the car transmission woks fine again for 5-10 miles.

the whole way home i was waiting for other symptoms or anything else to happen to break the pattern but nothing did. so is it fair to assume its the capacitor issue? i have to work tomorrow so before i stay up tonight tearing my glovebox out I just want to get your guys expert opinions.

thank you so much!

RA40

iTrader: (6)

Happy that Club Lexus has provided the support info you need.

Before you get into the glove box and dash, this test can be performed prior to check the ECU.
https://www.clublexus.com/forums/ls4...-by-yamae.html

Qwertyui1

LS I have followed many of your posts about solving this ecu issue and helping others solve their ecu issue. I'm determined to pull mine and check its condition and most likely replace my caps with the caps you specify. I own a 95 sc400, could you provide a list of the caps I need to purchase.

surfRider

Need some ideas.

I have a 93’ LS 400 that has been giving me headaches for a few months. My local auto repair shop could not find the problem. It starts fine but chugs at idle, particularly in gear with the brake on. It feels very much like a vacuum line leak. The power and acceleration are terrible but it runs and does not stall. The check engine light and TRAK-OFF lights will come on after about 15 minutes driving, stay on for about 5 minutes and then turn off and does not come on again until the cycle is repeated by starting a cooled engine. There are no error codes when checked. The engine coolant temperature needle takes a long time to get up to temperature and at about 25% movement is when the engine check light comes on. The instrument panel was rebuilt by Jim Walker a couple years ago. This all sounds like an ECU issue but here is what I have done:
1. Checked ECU capacitors before pulling the ECU and check was fine. Inspection of the caps looked good without any leaking, etc.
2. Replaced the ECU capacitors per specs on this thread, twice.
3. Quadruple checked my soldering connections.
4 Replaced the coolant temperature sensor (auto zone brand).
5. Sealed a cracked EGR tube and cleaned the EGR valve although the tube has been cracked for ten years.
6 Replaced plugs and ignition wires.
7. Had it smog checked and it passes all emissions with good numbers but is failed when the check engine light comes on. I am going to retry this Monday after an hour or so of driving.
8. Replaced a bad vacuum hose from a rodent bite.

Could it be a bad thermostat, possibly stuck open? Would this create a bad fuel mixture as the engine temp does not match the run time, just guessing at this point?

I am pretty good with cars (retired mechanical engineer) as I built a street rod and work on the engine of my ’76 Porsche among other cars but cannot figure out what the problem is and without any error code am sort of shooting in the dark.
Has anyone had this issue before and learned a solution?

RA40

iTrader: (6)

Would do the ripple test to check the ECU output. My other thought is O2 sensor/s.

surfRider

I did the ripple test as a first step and the output was within the acceptable window. I want to check the 02 sensors but am not familiar with the test points. I have read that the pre cat numbers should be about 0.8 volts.

Qwertyui1

Opened my ecu and it looks clean. No leaking caps. What else could be causing my car to be limited to 2 rpms with no engine lights besides my egr?

KawiLex

ok, I replaced the caps today on a 98 LS!! So far the car is running perfectly, where it previously wouldn't start intermittently and had speedo issues, as well as supposed tranny issues. I guess I can't call it good until I drive it for a week or so but it seems to run excellently.

I hooked the ecu and VSC back up to the power but left them dangling there while I test it out. At this point I'm seeing an airbag light on the dash and wondered if anyone had any ideas. Do I need to put everything fully back together?

Thanks!

BTW, none of the caps looked bad.