SnotRocket2

Hi Guys, Been searching and reading about the ecu cap issues FP ECU issues etc, no start so on. I've almost replaced many parts but the issue thats happening is odd.

SO it's a 93 SC400. I've checked the following parts and found no issue/proper voltage.

Fuel pump
FP ECU
Battery
EFI Relay ... this is where I solve the problem.

So the issue is first thing in the morning, I can fire up the car no issues, the tell is the CEL is on. Once ive fired up the car she runs perfect no stumble no idle issues nothing, good power and fine for my 1 hour commute about 45km (30 miles).

Once I shut it off, if I try to restart I get no CEL and endless cranking. Cranking is strong is as well. If I jumper the pins in EFI relay I believe it's 2 and 4 (12v and matching ground) the car gives me a CEL light during start up and fires up without issue. If I leave the car for the day (9 hour day) itll fire up without issue. I've replaced the EFI relay with the other 2 and no change, only way to get it to start if the relay isnt working is jumper. My last check which I've done but want to put under more conditions is the 5v reference in the other pin location, I know I have 5v but want to test after warm up if it's changed.

Other then that and the zero drivability issues im stumped. I've reached out to Tanin, but they've said it's an ECU replacement as opposed to a repair? I've not taken my ECU apart yet, but dont see why it couldnt be repaired since it works fine others? am I missing something or is there other trouble shooting steps. I've got a multimeter handy just need to know if there is more I should be checking.

LeX2K

Are you swapping in new or used relays? I got burnt on this swapped in a used EFI relay and thought my problem was gone it came back. New EFI relay solved it. Not saying that's definitely your problem but could be. No CEL means no power to the computer it's rare (or never) that the ECU is so dead you don't see the CEL with key on engine off.

Another possibility is corrosion on the terminals that mate with the relay. On the computer, you should get the caps replaced they are probably cooked at this point.

edit - I bought mine on Ebay it happened to a genuine Toyota part most are not. If you can't find another source go here
https://www.amayama.com/en/part/toyota/9098702004

SnotRocket2

thanks I've been looking for a place to pick up a new relay, for reference it's about $65+ CAD for the same relay that shows as $8-10 USD so I can't run and pick one up if you know what I mean.

Ill check the contacts and take apart the fuse block.

TaninAuto

If it is in fact the ECU that is the problem, on an SC400 ECU by the time the CEL doesn't turn on or fades in and out intermittently, or works sometimes there is so much corrosion and leaking capacitor damage on the board it's no longer worth our time to rebuild and repair. That is why we recommend a replacement.

There is probably a couple hours of labor at least to fully clean up everything and repair the damage in there. Then once we spend a few hours repairing and rebuilding something like this there is the possibility it still doesn't work at all, properly, or partially. Then we are in an even bigger hole. With everyone charging bargain basement ECU rebuild pricing these days the risk vs reward and labor cost exceeds any profit in something like that so we just pass.

SnotRocket2

@TaninAuto, thank you for the explanation. I was curious what would make the difference and based on your having significantly more experience in this area I appreciate what you are saying.

Ill be in touch with your team regarding replacements.

SnotRocket2

100% leaking caps. the question is can it be fixed or totally garbage?

Im already in the works of getting a replacement via Tanin, but wanted to know if this one can be saved as a spare cause finding ECU seems to be very difficult these days.

Thoughts?

TaninAuto

The capacitors are the easy part and can be fixed in about 15 minutes. The check engine light problem is not related to the capacitors, but the secondary damage that the leaking capacitors caused all over the board. That is where the additional hours of labor come.

SnotRocket2

@TaninAuto Thank you guys for getting me a replacement ECU, car is back running mostly as it should .. only had one time so far where it was idling fine and shut off. restarted fine right away and hasnt had an issue since, but i havent done as much driving as I would have liked as the bushing for the trans to rod lost it's cotter pin and I couldnt shift the car. quick fix this weekend and it's back til I can get proper parts to fix it.

Another week coming of commuting.

Thanks again! no more jumpering in my future :fingers crossed:

MatClever3

Not completely true!!! Mine was far worse then the ECU in these pics. Was also told it was beyond repair by 2 companys. I repair it myself and solved all my problems and took care of the engine light.