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Discussion Starter · #1 ·

I have a 2000 Outback Limited Sedan that has 120k miles. Fairly good condition, though parts are wearing out faster than I would like. Recently, I have had problems that seem to be electrical in nature. My Subaru dealership can't find anything wrong and recommends replacing both the TCM and the ECM (TCU/ECU) next time it happens. It was in the shop for a couple of days last week while they checked things out.

About two months ago, the AT Oil Temp light came on (solid, not blinking) while I was driving home from work. Not having seen that one before, I pulled over and turned the car off while I dug into the manual, which said "don't go up steep hills or pull things". When I turned the car back on, the light didn't come back on.

Then, two weeks ago, the AT Oil Temp light came on flashing. Restarting the car again cleared the code, but it came back within a few minutes along with the check engine light. I took it in to the shop where they couldn't find anything wrong with the AT system except for dirty fluid. They replaced the fluid, cleared the code (I forgot to ask what it was), and off I drove. Last monday the same thing happened, so I took it back in. Supposedly it was a different check engine light code (again, forgot to ask....) They spent some time checking the electrical system, and generally rooting around, but again couldn't find anything specifically wrong.

To me it seems obvious there's some electronics that are going wonky. The only suggestion the dealer has is replacing TCM / ECM for $1600 (!!!), which would be the straw the breaks the camels back -- and makes me get a 'new' used car.

The battery was replaced last year, the car is driven (for the last month) ~40 miles a day to work and back, and before that it was 14 miles daily. I have a multimeter and I'm not afraid to use it, and I have a Haynes service manual, but that doesn't have anything obvious for me. Oh, thought I'd add that I've had the head gasket leakage issue fixed about a year ago as well, as well as a right outer CV boot fix recently.

Does anyone have any thoughts as to things to check? I'm considering replacing the TCM (looks like $100 off ebay) myself since the manual indicates it's fairly straightforward and no programming is needed. Is this a good "first" step if all else fails before replacing both at the same time?

Thanks in advance!

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Discussion Starter · #8 ·
Get the codes read first, and post them here. It might be something other than the TCM or ECM, without knowing the codes you would be just throwing money at parts you may or may not need to solve the problem.
I was afraid that was going to be the first question :). I'm checking with the dealership, and will post when I hear.

Using the instructions in this thread you should be able to read the transmission codes that would have been set with the flashing AT Oil Temp light.
Thanks for those instructions. I followed the instructions and was able to get the "2 flashes / second" i.e. "All Clear" signal from the AT Oil Temp indicator.

Start by trying to pull the transmission codes and see what that provides.

Like others, I doubt the problem is in the control modules.
Good to know. I actually wonder if it might be related to the cruise control. I had been using it (I think) when the check engine light kicked in (though not always with the flashing AT Oil light...). I'm avoiding cruise control for now, so we'll see.

the ECU is just as easy to replace. if you can do one you can do the other. ebay is one source, Auto Parts Market is another.

good luck and let us know what you learn.
Do you have a reference on how to get below the carpet on the drivers side (I believe that is where the ECU is)? My Haynes manual doesn't seem to have that information (unless it's hidden somewhere not-obvious).

Thanks for the link - I did find a used one for $200. That would certainly save me a lot of money if I need to do it!!

Thanks again everyone for your responses. I'm trying to track down the codes, and am certainly considering getting this ODB2 reader from amazon: U380 OBDII Check Engine Auto Scanner Trouble Code Reader : : Automotive ... though that one wouldn't work with my newer subaru... but it's the right price...hmm, might have to wait for that.

Again, thanks all!
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