SGWilly

My brother gifted me with a 98 in fair condition. It ran pretty good but would stumble at times. Felt like intermittent ignition. I had no codes and decided to take a stab at replacing the capacitors since that process was so well documented (like a sneaky trap). Afterwards, the car ran the same with intermittent stumbling at times (oh well). And then after about a week of daily driving, while at speed I heard a pop, saw a puff of smoke in the cabin and ignition when entirely out. Motor turns over - nothing fires (crap).

I tried hooking up 3 different ECM readers and couldn't make a connection. I then sent the ECM into a repair service and they informed me the board "was burnt up". Sooooo, I purchased another used ECM and plugged that in.

And here's my question - my code readers (which work fine on other vehicles) fail to establish communication with the replacement ECM. Is that normal or should I be able to connect? I'd like to know that before I send it into yet another service to match the keys to it (which is pretty expensive). If that isn't normal (which is what I suspect) AND I assume the replacement ECM is working, then what next? Is it in my wiring harness? Any thoughts/suggestions welcome but I have to tell you - I'm not inclined to have it towed to a dealer.

-Steve (DIY is a sickness at time).

oldskewel

iTrader: (1)

Sorry to hear of the problems.

Not clear from your post - does the car run now? Is the lack of OBD2 communication the only issue?

I've got a '91, with no OBD2, so I can't help here, but I would bet that some people on here know a lot more about your problem than the dealer would. Hopefully you can get the help. And the dealer would probably hook it up to a machine, see nothing, shrug, and give you a diagnostic bill for $140 and an estimate for a $2100 ECU replacement, with no guarantee that it would fix your problem.

Also, a guess on the blown ECU - most likely that you accidentally wired at least one of the capacitors in backwards. They have a polarity, which is perhaps easy to mess up.

billydpowe

iTrader: (1)

are you using an ODB2 reader on this??

SGWilly

The car hasn't fired on one cylinder since the puff of smoke incident.

My most recent scanner is an Autolink AL619. Fully compatible OBD-II.

Yamae

I know some about the ECU and may be I can give you some advice if you could give me more details.
I still don't get your current situations well enough.

Q1, Are you in use of the ECU which you purchased newly after giving up to fix the original and the immobilizer code is set?
Or are you in use of the original ECU which smoked?

Q2, Are other 7 cylinders working now?

Q3, Other than to use scanners, have you tried the traditional way to read the code only using a metal clip at the DIAG connector under the hood?
If done so, inform me the result. If you don't know how to do it, search the net and you'd find the way.

PhilipMidd

[QUOTE=Yamae;10351331]Q2, Are other 7 cylinders working now?
To Yamae. I'm sure what he meant was it has not fired at all since the ECU smoked up.

SGWilly

To answer all you questions Yamae,

Q1, Are you in use of the ECU which you purchased newly after giving up to fix the original and the immobilizer code is set?
Or are you in use of the original ECU which smoked?
I do not have the original ECU which smoked but I could get it back if needed.
The replacement ECU I currently have has not been matched to my keys so the immobilizer code is keeping the car from running. What I am concerned about is I can't establish communication with the replacement ECU.

Q2, Are other 7 cylinders working now?
Phillip is correct. The car has not run on any cylinders since the initial issue.

Q3, Other than to use scanners, have you tried the traditional way to read the code only using a metal clip at the DIAG connector under the hood?
I have not but will try. I haven't used a paper clip jumper since the 90's.

EZCarKeys

Are the original AND replacement ECU part numbers the same? If so, I'd suspect a bad replacement ECU, wiring, or fuses. Check the fuses first, since that's the easiest.

Fit1too

I wondered the same thing. Here is the post with all the part numbers: https://www.clublexus.com/forums/ls-...ml#post8762081

Yamae

When you use a replacement ECU, the immobilizer code in the ECU should be re-written to match your key by a dealer or by someone who can do it. Without doing it, the ECU has no idea to work fully and the igniters are not driven at all. It is natural that any cylinders don't work. There is another way to use a replacement ECU replacing the immobilizer chip picking up from the original ECU and mount it on a replacement ECU. This method can be found in a Youtube video. But the original chip should not be dead while smoking.

Anyway, I'll wait until you inform me the result of Q3 to confirm the basic.

SGWilly

All my fuses are good (ECU-A in cabin, ECU-B and ODB in engine bay).

I tried the jumper wire on the diagnostic terminal in the engine bay following your post #26 here. I tried it 3 ways; 1) jumping just the engine bay terminal, 2) jumping just the odb terminal, 3) jumping both at the same time. None of them displayed any flashing engine codes on the instrument panel. I do not believe it entered a diagnostic mode as I saw no "EFI" message on the display after pressing the function button. I also so no flashing check engine light which is what I've seen other cars do with a jumper on the diagnostic terminal.

I did not realize that the model # was anything other than "1UZ-FE". The replacement ECU is 89662-50010 which I don't see in the table Fit1too posted but appears to be a fit for a 1998 LS400 according to other sources on the internet. I'm not sure of the original ECU number. I'll get it back from the repair service to compare those numbers. I'm also hoping to swap over the immobilizer chip (if I correctly understood that to be an option).

I am aware that the immobilizer disables spark ignition. I do not expect the replacement ECU to allow spark ignition at this point. I did expect the replacement ECU to be able to communicate with an ODB-II scanner. That is really my question - should a replacement ECU be able to communicate with an OBD-II scanner even if the immobilizer chip has not been set to the keys?

Thanks for all the help so far.

Yamae

So the replacement ECU is not OK to read the code. I haven't tried that using an ECU which doesn't match the immobilizer code and I can't judge.

Anyway, the ECU 89662-50010 is for a 98 and has the updated firmware. As long as the immobilizer code is matched, it should work if it's a good one.

Incidentally what was the reason why the original ECU smoked? Did you mount every capacitor correctly? Electrolytic capacitors have a polarity and it should not be reversed when you mount. When reversed, chemical reactions occur and the heat is generated and accumulated. Then the safety valve opens making a pop sound. When it pops, the internal liquid and the materials come out causing surroundings to be a mess. The liquid is often vaporized by the heat and it looks like a smoke. Sometimes it happens in a minute and sometimes in hours after the power on. Depending on circuits, it takes more time if the current to the capacitor is very small.

This is just my experience and I don't know it's applicable to your original ECU or not, but generally speaking a good intensive cleaning and fixing damaged traces revive the ECU. This needs some skills and patience to do though. Is it possible for you to take photos of damaged part of the ECU and show those to us?

EZCarKeys

YES, the ECU should still communicate with a scanner if the immobilizer is active and not receiving a good key.

SGWilly

Yes, once I get it back I'll take some pictures.

I replaced the capacitors hoping to fix some erratic misfires. I was very careful to get the polarity orientation correct when replacing the capacitors. However, my soldering iron was not very effective and I ended up putting a lot of heat on the board to move things around. In fact, one of the traces lifted and broke where a capacitor lead went. To bridge that gap, I put a larger puddle of solder down. More on that when I can post pics of the actual board.

I don't know the reason the ECU smoked. It happened quickly. The engine stopped firing (I was traveling about 40 mph) and smoke appeared within 2-3 seconds. No traces prior to that.

I'm starting to believe that the issue may be within my wiring harness. Seems that the ECU is fairly airtight - enough so that any smoke would have come out slowly over time and not all at once (which it did for me). This would also explain why both ECUs are not communicating with a scanner.

SGWilly

I got my original ecu back and it isn't pretty. I must have shorted some of the traces with my poor soldering skills.



I'm guessing this board is not repairable - so two areas of questions...

1) Could this short also have impacted other components of the electrical system that would keep my replacement ecu from communicating? Any suggestions on where to start looking? Does anyone have an picture of the wiring harness components? I've downloaded a bunch of pdfs from the Toyota service manual portal but I'm having a hard time navigating them to find the right information.

2) Can the immobilizer chip be moved from the old ecu to the new one to match the current keys? Is there a link on how to do that?

Thanks,