t2d2

iTrader: (8)

Thanks for confirmation on Trac. I was thinking it must just be a piggyback system. That doesn't leave many things to potentially differ within the model lineup...

Are you sure about OBDII not being until '96? I could've sworn I read that Lexus adopted it a year early in '95, which would mean it's showing up on mid-94 build dates.

Mine is definitely a '93 build date, and Federal Emissions as far as I can tell. I don't think there's any more that Toyota or Lexus would be able to tell me, unless I got lucky and found someone intimately familiar with the ECU differences within the '94 model year...

#89661-24410, #89661-24231, and #89661-24240 are all 40-40-40 pins. It sure seems like newer ones would be backward compatible -- in which case, why not go with the newer programming -- but it's weird that there are no compatibility charts to be found.

I have received responses from a couple of repair services now, and it's a mixed bag of repairable, shot, and TBD upon receiving it. I sort of think replacing it with a non-deteriorated one is my better bet, but I'm still awaiting clarification on some follow-up questions.

t2d2

iTrader: (8)

Got some unexpected good news today. The tech was going to put the old capacitor back in and button it up so I could run the car while searching for a replacement, but he felt really bad that he couldn't fix it over the weekend and decided to forge ahead. When he called, I thought he was going to tell me to come on over and pick it up. Instead, he said he had de-soldered all 120 pins, rebuilt the traces and corroded pins, and was in the process of replacing the rest of the capacitors and putting it all back together! I'll know in the morning how good his work is, but I'm pretty encouraged by the news so far.

He was able to do it without removing the 6 screws on the bottom of the back board that are soldered into place at the factory (so you don't unscrew the board and unwittingly tear it off the pin connections). He thought that was going to be the hold-up, not having the proper oven and protective gold tape for targeting those spots.

KahnBB6

iTrader: (5)

That's good news! I hope he gets it right. If he does you'll be in good shape.

As for OBD2, it was definitely a 1996 model year change for ALL US cars. No manufacturer was spared the changeover. 1995 vehicles with mid 1994 build dates should not be affected-- only model year 1996 vehicles.

If yours is a 1993 with Federal emissions you are fine to stick with an OBD1 ECU. For reference, I wouldn't use the Cali ECU on your car but between the other two I can't say. I'd just go with whichever more closely matches your car's build date unless there is a known advantage to using one of the newer OBD1 ECUs.

t2d2

iTrader: (8)

That's the million dollar question. And probably next to impossible to get a conclusive answer to.

I got the repaired ECU back this morning, and so far so good. He showed me the before and after pics of the damage and his fixes, and it was both extensive and impressive. He found leakage under two of the capacitors and more cleanup that was needed under one of the microprocessors, in addition to the water damage at the bottom of the board.

As long as there's no damage to the barrel connectors between the multi-layered board (where the capacitor legs go), he figures everything should be in tip top shape now. Hopefully, that means no more looking for replacement ECUs... Damage to the barrels would be pretty difficult to determine and fix.

Moral of the story: If your ECU is all original, don't bother inspecting it. Just go ahead and replace the capacitors! They only have a 10-12 year shelf life according to the expert, and none of the damage was visible on my boards until they were removed.