blackroadster

I did list out the steps as I understood them in my post. Can anyone clarify the process?

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.

Thank you. Got the TCU out. The ECU looks buried!

Whelp... It's Baaaaack. It was working completely normal when I went and filled up with gas around the corner. I filled the car up and 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. Car is stuck in 1st gear. I limped the car home 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 located. Under the dash, near the steering column is a gold colored box. I would have thought its the ECU. I don't see anything under the passenger side dash that looks like a computer. The only thing I've found is the 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.

So... I left the car's battery unplugged for several days and unplugged the harness connection on the top of the transmission. All the contacts were shiny and clean. As I was connecting the battery I noticed a ground wire I had left unattached when I replaced the battery harness a day prior to my problem. Had I just reset the TCU or do you think the unconnected ground wire was the culprit? BTW, the Power light works fine now. I suppose I should check the codes but the transmission is currently working as normal now.

I am in Allen, north of Dallas and having this same exact problem! I just posted about it in the forum. I was thinking my problem is TCU related as well. (Damned Horned Frogs!) <---Texas Joke Anyways, SUBARU3, you seem knowledgeable and you're local. We should meet up! I'm new to Subarus. Love my little Legacy SW and want to get it driving again.

Hello Subaru people. I recently bought a 1990 Legacy SW from a friend. Its a FWD Automatic. All maintenance was up to date and had been a reliable car but with the associated 30 year old car problems. Various worn out switches, cosmetic wear and tear and such. The car doesn't leak a drop of any fluid except water from A/C condensation and strangely a lot of water. Without any warning the transmission would only go into 3rd gear (4EAT). Checked the transmission fluid, which is very hard to read 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 ok. 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 today and it appears stuck in 3rd still. 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'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. Subaru Gurus do your thing.