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Old 09-19-2020, 11:36 PM   #1
blackroadster
Scooby Newbie
 
Member#: 518713
Join Date: Sep 2020
Location: Allen, TX
Vehicle:
1990 Legacy SW
Red

Unhappy 1990 Legacy FWD 4EAT Problem

Hello Subaru people.

I'm an owner of a 1990 Legacy SW FWD Automatic. All maintenance is up to date and had been a reliable car. The car doesn't leak a drop of any fluid.

Without any warning the transmission would only go into 3rd gear (4EAT). Checked the transmission fluid and it appeared low but clean. No burning of the ATF and it was a nice red color. I warmed up the trans, shifted it into several gears and rechecked. I added more ATF until it appeared full. I drove it home and about 10 minutes from home, it got stuck in 1st gear. I limped it home and parked it for about two weeks. I drove it again and it was again stuck in 3rd. Park, Neutral and Reverse still works but selecting any other gear does nothing. I tried to check TCU codes but the "POWER" light never comes on. I left the car's battery unplugged for several days and unplugged the transmission harness connection on the top of the transmission. All the contacts were shiny and clean. After reconnecting the battery, it was working completely normal when I went and filled up with gas around the corner. I decided to try and diagnose any TCU codes. I used this method. After performing the steps twice I noticed power light did not illuminate anymore. Car is again stuck in 1st gear.

At this point, I'm at a loss. How can it work just fine and then go to complete crap again? No chewed wires that I can see. I'm still at a loss as to where the TCU is actually located. Under the dash, near the steering column is a gold colored box. I would have thought that is the ECU. I don't see anything under the passenger side dash that looks like a computer. The only thing I've found is a small photo but it doesn't really show me where it's located. Looks like maybe the back seat? Almost looks like a power window motor in the lower left corner of the photo.



I'm thinking a failed TCU may be the culprit. Where is this box located? I have also considered doing a 5MT swap but it is more involved. Since this is just a spare vehicle and my hauler, I want to do the minimum to get it back to being the reliable vehicle it was.

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Old 09-19-2020, 11:36 PM   #2
blackroadster
Scooby Newbie
 
Member#: 518713
Join Date: Sep 2020
Location: Allen, TX
Vehicle:
1990 Legacy SW
Red

Default

Mods please delete this reply to my post.
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Old 09-24-2020, 09:05 PM   #3
blackroadster
Scooby Newbie
 
Member#: 518713
Join Date: Sep 2020
Location: Allen, TX
Vehicle:
1990 Legacy SW
Red

Question

So I bought a used TCU on eBay and replaced my TCU.* I*get a POWER light on start up.* I test drove the car and transmission is shifting through all the gears.* The shifts are a little harsher than I remember but maybe the new TCU is learning?**

Anyways, I warmed up the car and ran through the test to check for TCU codes.*

Ignition off / Ignition on / light on / drive above 12 mph / Ignition off / Ignition on / Shift to 1st / Ignition off / Ignition*on / Shift to 2nd / Shift to 1st / Shift to 2nd / Shift to 3rd / Shift to Drive*

No codes and no POWER light.**

Started car and got 16 quick flashes of POWER light.***I tried pulling the codes again with the same results.**

Transmission still working in all gears after about 3-4 miles.* I'm nervous to drive it far.* The 16 flashes has me concerned but no TCU codes.**
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