Resolved 1G Can't find my TCU

[MadMar23]

OK, this is an all-time new for me. I absolutely can't locate the TCU nor it's 42 pin plug/harness. Could it be under the piece of carpeted plastic way in the back bottom area under where the ecu is/was?

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According to the Vin dicipher, the 4th digit is C denoting that it's definitely an automatic transmission car. So.... Where the heck is the TCU?

 

[steve-o_95_GST]

The TCU is on the "floor" right up against the firewall in the center of the vehicle. You'll have to pull the kick panel off to get to it.

 

[MadMar23]

I pulled off both side kick panels. Took out the ecu. No TCU under the ecu.

 

[19Eclipse90]

According to the Vin dicipher, the 4th digit is C denoting that it's definitely an automatic transmission car. So.... Where the heck is the TCU?

The 4th digit tells you what type of seat belts you have, not what transmission type is in the vehicle. This is from the 1990 FSM.

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[dwb]

Why not visually verify if it has a manual or automatic? The vin doesn't tell you what's been done to it over the last 30+ years.

 

[MadMar23]

Well heck. Sorry but I'm pretty old and haven't messed with this in 5 years... I finally got the son of gun out.

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Now... Look at this board. Does anything look bad?

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[19Eclipse90]

It appears, at least, to have some capacitor leakage to C24.

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[steve]

That's a shame, another EPROM TCU where the capacitor leaked and took out the voltage regulator and blew up the processor and port expander.

You can see the bubbles on both from when the magic smoke tried to get out.

 

[MadMar23]

Hmmmm.... OK... Here's the story. Son bought this car for $600 about 11 years ago. We actually drove it from Miami to Sebastian running on 2 cylinders. I swapped in a built 4g63 I had bought from my friend T from Pennsylvania and actually ran it in a 2g before it killed the transmission. I parted out that car but kept the engine. The car did run for a few days them the transmission started acting up so I parked it. Sat in my garage for 5 years.

About 2 months ago, I pulled the VB (which had a half-assed shift kit installed) and sent it to Andrew at TAU. He rebuilt and tested it and certified it as good. I reinstalled it, no reverse and still stuck in limp mode.

Mind you, I'm almost 70 now and working on these cars is very difficult but I do eventually get it done. Only took me 3 days to get that TCU out.

I realize it's possible the W4A33 is bad and I'm ready to buy a good strong trans if I could find one or a new one from IPT. But, if it's a bad TCU, well.... I'm willing to replace it (totally unfindable) or have it repaired.

That's my story and I'm sticking to it.

Might anyone have a good MD750092 or recommend someone who can repair it?

Does anyone know the fellow on eBay? I just Msgd him to check his pulse.

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[steve]

I wish you luck.
I've found that once that capacitor leaks the voltage regulator dumps 12v on the 5v rail and fries everything. I've tried repairing them in the past and never managed to fix one once that failure happens so I stopped trying to do TCUs due the very low success rate.

I'm betting you'll need a full replacement and while you're at it make sure to get the capacitors in the ECU changed too. 1990 ECUs have a tendency to burn up when the main input filter capacitor drys out and shorts. I haven't see that happen on the later 91+ versions. The capacitors leaking is an endemic problem with electronics from this time period not just Mitsubishi ECUs and TCUs.

So check the ECU, it looks like it might have been replaced ones already and if so make sure it had them done and done well. Many "Repair" shops operate on the model of get a bunch from the junk yards, do the least amount to them and pull one off a stack when a repair comes in. They don't care if it lasts, they just send another off the stack, if the customer bothers to come back for warranty.

 

[steve]

This 90 ECU started burning from the C106 leakage at the SMD capacitor in front of it. Usually the fire starts right under C106 between the three holes. One is +12, the middle goes to one of the coils on the Idle Speed Control Motor, and the last is Ground..

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This one caught fire under both main capacitors from them leaking.

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This is the typical case for a 90 ECU if left too long.

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Like I said the later (91-94) ECUs don't tend to burn when failing.

 

[MadMar23]

Thanks, Steve. The Ecu was serviced and chipped by ECMTUNING about 7 or 8 years ago and the car has been in my air conditioned garage since. It starts right up and runs great. I did a ton of work in the engine bay and interior.
I'll never find a decent MD750092 so I guess my only option is to try the ebay guy. Or.... Forget about it and go with a ForcedFour Smart-150.

We're leaning more towards the Smart-150 because it's fully programmable and a toggle can be added (and paddles or 3g tiptonic shifter) to switch between softer pressure regular driving or full 100% pressure shifts for those pesky green light encounters with someone who understimates my sleeper looking Talon.