My son has an Aristo (I know I know this is a GS forum) that has a pulse issue to injector #3 and was told it was a bad ECU after a few other typical symptoms of one going bad had developed. He replaced said ECU with one from Japan.

Same exact issue. Way too much fuel being squirted into cylinder #3. He has found a 3rd ECU but I'd like to know where one could get an ECU diagnosed or repaired for a time if my 04 GS300 decides to quit.

I know in time Honda ones go bad after solders get brittle and begin to lose contact. I'm figuring Toyota/Lexus circuit boards probably do too. Honda cars litter junkyards galore so finding one that works is no biggy.

But does anybody reading this know where one can get a Toyota or Lexus ECU diagnosed and/or repaired?

Thanks for any response.

 

You can try to repair the ECU with a service like that on eBay.
https://www.ebay.com/itm/Lexus-ECU-R...-127632-2357-0

 

Hello,

To have two independent ECUs fail in the same exact fashion is extremely unlikely, unless it is either a common thing on those cars or there is something else frying the ECU. It does not seem like a common malfunction on those cars, so before risking another unit, make sure to measure resistance of the injector and wiring from the ECU, you can also take old ECUs apart to see what might have caused an issue like that.

Hope this helps and best of luck!

 

Thanks for the replies Aegean and Arsenii.

Well it turns out many Toyota/Lexus models are plagued with a failing capacitor in the ECU so the likelyhood of the dice coming up snake eyes twice in a row with these is apparently not uncommon.

Here's the list.

 

While it is true, I am still not convinced that two separate ECUs that came from totally different cars would have the same exact flaw, at least something must be different. If you look at the list of issues that could happen as a result of bad capacitors, it is pretty much endless, so the odds of you getting an ECU with the same injector failed twice in a row are vanishingly small. In any case, even if it is an ECU fault, it will never hurt to verify that everything else is working as intended before you will go risk your new unit, just for a peace of mind.

Hope this helps and best of luck!

 

I'll second this. I'm not convinced either, yet. lol
While I've seen strange things so anything is possible, I would like to see the injector waveforms on a oscilloscope to compare from one cylinder to another to be sure.
The injector pulse lengths should be the same on each cylinder across the bank as seen on the scope.
Just some ideas.

 

Thanks!

The ECU will arrive in a few days. If that doesn't solve the issue we will go another route. So far the shop has replaced the o'ring on #3, that wasn't it, then 2 known working injectors swapped onto the rail and same results so my son ordered a 3rd ECU since some of the symptoms of a failing ECU also showed up in #2.
Both were for 93+. The one on the way is for 91/92. I did not mention in post 1 it's a 92 model.

One thing that kept us and now the mechanic from running the engine very long is fuel is loading up cylinder 3 and running into the exhaust pipe. Yikes!

 

Did the mechanic check to make sure the injector wire for the bad cylinder wasn't shorted to any other injectors?
It could be pulsing too long like originally thought or maybe it could be pulsing multiple times do to being shorted to other injectors which could in theory happen in the wiring harness or the ECU and flood that cylinder.
Multiple pulsing could quickly be seen on a scope too.
Yeah I know crazy theory but just thinking.

 

Good suggestions, thanks again.

So since it's my sons car and he speaks with the mechanic periodically I'm not sure what has been tried up to this point. We do not know for certain cylinder 3 was the issue but do know it is now.

It seems to me the mechanic is working on it in between jobs he knows what is wrong and can fix it, then get the customer back their vehicle. For my son it's a Sunday driver so he is in no hurry.

What I do know is an ECU was giving my son grief but then one day the car ran like crap with no code and fuel smell very strong. What cylinder or cylinders were affected we do not know. It acted like a vacuum leak. He and I checked over a few things and when it got beyond our realm he had it towed to the foreign car shop. But he had swapped in another ECU before that. The ECU he swapped in also showed some signs of issues.

The mechanic noted where the fuel was coming from and replaced the o'ring, which did not solve the issue. My son took a new set of injectors to the shop and the mechanic tried two with the same result. So the idea is next week swap the 91/92 ECU in and see if that solves the issue. If not the mechanic will begin trying to find the issue in what we would presume is a wiring issue.

What ever the outcome I know those ECU's have issues and I'm hoping to find a place that will replace all capacitors with new ones on one of the leftover ECU's.

 

Just reporting back in;
The 3rd ECU solved the issue.

And my son reported that he found a tinkerer friend of a friend who is going to rebuild the first ECU.

Thanks for everybodies input.

 

Hi friend,
This is exciting news and thank you for posting the update.
Reason this is interesting is because it is rare for a circuit board to fail in the same exact way twice when there are so many wires and peripherals with thousands of components and solder joints unless there is a design flaw or something more interesting going on.

It's rare but some of the boards I work on always have the same components fail first before everything else but these components are usually passives(caps) or hard working components related to Vreg circuits that shut down many things and not so specific as you are experiencing- which makes your posted fix more fun.

Please let us know what the tech finds, could be a good reason such as the lucky placement of a capacitor that tends to fail and leak juice on the trace that goes to #3 injector or something like that.
Also could be a 1 in a million bad luck but I'm guesing chances are there may be something unique about the injector #3 part of the circuit and a pattern may emerge on this car's ECU.

 

For clarification, we do not know for certain it was #3 that had the issue before, but do know there was one mis-performing. It was after the mechanic had taken things apart and reassembled that he had pinpointed it to #3.

The car began to have issues a few months after he bought it, but ran fine. Just random stuff. But one day it ran like doo doo. And a strong unspent gasoline smell wofted from the engine bay. He swapped out something known to cause issues, a pressure regulator or something that is vacuum operated. A part that had melted. Apparently common with that engine. That did not solve the issue so he did what his buddies at the Supra forums suggested and swapped out an ECU. Again that did not solve the issue.

Now, from what I understand the ECU had been rebuilt by a company who does not have a good reputation for reliable repairs. He bought it from a 3rd party. And when that did not solve the issue he had it towed to a shop that specializes in foreign car repairs.

I had gone over the engine bay with my son looking for wires frayed or issues with connectors. Things like that. We tested a few things too, all the while my son saying "dad, it's probably another bad ECU".

One thing I've learned over the last 10 years is my son knows a lot more about the electronics in Japanese domestic market sports cars than I ever will. In a way I'm glad he was right. His turbos have begun to spray oil a little bit and I was afraid oil had gotten into a non-weather tight connector…but which one? There are so many.

So now to solve the turbo leak issue. The Aristo is popular with people who like to modify their drive train so finding answers when something stock malfunctions is like finding an honest politician.

 

do you guys think that my issue could potentially be the same??
I just bought a 1995 GS300 with 216,000 miles for $350 (chu-ching) and it doesn't run. It will crank and as it cranks it sounds like it's misfiring like only 1 cylinder in firing, kind of a weird sound, I have never heard it on a car. The previous owner told me that he was driving normal, no issues, pulled off the line to accelerate and it lost power. He pulled over and had to TURN IT OFF. Then went to start it again and it wouldn't fire. I figured it was a fuel pump so I tested that first and it had zero psi lol. I thought I was done and tried to start again and got nothing. I double-checked fuel pressure at the fuel rail and it was gushing fuel everywhere so I started looking around some more. I looked at the timing belt and it appeared to be worn out and then saw that the exhaust cam and intake cam had both advanced one tooth (I don't have pics sorry) so then I replaced the belt and put it back in time. Tried to start it again, and still nothing but now the misfire sound I mentioned earlier sounds better as if 3/6 are firing??? I don't know. I checked spark and they all had spark, I checked the injectors (listened to them fire with a screwdriver while someone cranked the engine) and they all sound good, and the airways look good leading to the intake. I have checked other simple sensors but didn't get much out of them. I replaced plugs and wires while I had things taken apart. I have tried starting with starter fluid and got no change. Also, I didn't do a compression check because I started putting things back together after I fixed the timing belt think I was done and didn't wanna take it apart again to do it lol. But I will do it if someone recommends it.

I am trying to come up with things that make sense to me of what it could be. Could it be a bad ECU? Did I blow a head gasket ( I feel like it would still start even on a blown one with starting fluid and new plugs. Plus if the previous owner said he tried to start it again after it initially broke then I think it would have gone there too because that car was already warm... just my thoughts)? Cam position sensor/Flywheel sensor? This last guess is wild but maybe it jumped a gear on the timing belt, and fell into limp mode and shut the fuel pump off and won't let itself start... (honestly I don't even know what limp mode is on cars or symptoms of it so...) again these are just fun thoughts I have while I work.

Thanks for your help in advance!