I have been on vacation this week up in the mountains of western NC. On the drive up and back, I had the same thing happen, for the first time in nearly eight years of owning the 2013 Outback (smaller engine).

All of the conditions were very similar. About three hours since the last break, 94-96 degrees outside and averaging between 80 and 85 mph (not passing anyone, just keeping up).

Fuel light came on with about 60 miles or so on the sensor. Within five minutes, the transmission oil hot warning came on, not something I had ever seen.

Are these systems somehow interconnected?

As soon as I stopped, idled the light turned off. Filled up, no warning the rest of the trip with the same conditions as above.

The transmission fluid is cooled by engine coolant in the radiator. (It doesn't mix with the coolant, there is a little heat exchanger inside the lower radiator tank which is surrounded by coolant.) It is possible the engine is running hot under the driving conditions you describe. Subaru doesn't put temperature gauges in many of their cars, so the engine could be near boiling over but not enough to trigger the warning light. When you slow down and take the heat load off, the coolant, therefore the transmission, cools down. I don't know what the low fuel warning light has to do with anything.

It might be worth it to find out if there is a factory add on transmission cooler. Sometimes they were standard on another model and still can be plug and play for yours. Are there any enthusiast websites for Subaru's you could ask at? This could be a common mod.

For my old car, this is the case. The input and output lines are made such that they still route the fluid through the stock in-radiator cooler (described above) before going through the low, front mounted auxiliary cooler and back to the trans. So there is only one different line to replace. I am still searching for this setup from a salvage yard.

I do not believe your light going out was related to anything other that stopping. Any more is just confirmation bias IMO. Like on the movie Airplane!, the light might well have have been saying 'A Little Hot'.
As far as an add on cooler, there are some who will say if it needed it, it would have it. Fine. But cooler transmission fluid is never a bad idea. Especially in Texas (or Florida) in summer. And I don't think you'd have seen that light if you had a aux trans fluid cooler.

I would, at the very least, change that transmission fluid and see what the drain plug and fluid condition reveal.

egregore,
Mine does have a temp gauge, which has never gone beyond the middle of the range (hopefully working properly)

83v45
I have to look at my most recent service receipt (always done at the dealership). I think it was due for a transmission flush. Wonder if it wasn't the same spec? Will ask as this trip has put me near the next service. should also check the level of fluid.

In any case, the mere coincidence of happening twice under nearly identical circumstances has me saying "hmmm"

quote:

Originally posted by dlc444:
egregore,
Mine does have a temp gauge, which has never gone beyond the middle of the range (hopefully working properly)

83v45
I have to look at my most recent service receipt (always done at the dealership). I think it was due for a transmission flush. Wonder if it wasn't the same spec? Will ask as this trip has put me near the next service. should also check the level of fluid.

In any case, the mere coincidence of happening twice under nearly identical circumstances has me saying "hmmm"

Well if it is close then I'd just go on and do it. Modern transmission fluids generally have to be changed pre warmed (as the fluid expands) and have to be monitored for temp so it is within a certain range to be judged to be at the right level. It also may not have a dipstick at all.

Also, there may be condition codes present that could indicate other things like that fluid temp sensor may be starting to get a little out of bounds. Enough to make it sensitive, but not enough to trip a 'hard fault' and a warning light, specific or general.

I will inquire 83

Just adding, the wife has been driving a Suburban or Tahoe for years. She liked the outback much better in the mountains. More connected to the road.

I interpret that as not sitting four feet off the ground with a posh ride and feeling like you are in a 23 foot boat in 5 foot swells

A hot transmission can be either torque converter lock up slippage or an open torque converter clutch or worse like forward clutch pack slippage.

Mountainous driving can cause the torque converter to run unlocked.

Is it a planet drive or CVT drive transmission?

CVT drives require the fluid to be changed with factory specific fluid at regular intervals. My Juke had severe problems until I put Nissan fluid in it. It was slipping severely.

I've run a 2008 Impreza 90mph+ through a 110˚ desert for hours at a stretch and have never seen the light. 2.5L H-4 non-turbo, SportsShift 4-speed transmission.

You said ON vs FLASHING. Just speculating here, but the display may have indicated the fuel temperature sensor was kicking out a code. I know Subaru likes to double up indicators, like a flashing VDC and disabled cruise control indicated P0457, loose gas cap IIRC.

When you filled back up, the pump was again immersed in fuel.

If fuel temperature appears much higher than ambient temperature, a P0183 code will be stored and a malfunction indicator lamp (MIL) may be illuminated. https://www.obd-codes.com

Marzy, I have no idea. This was on the highway, I-75 to be exact. (Drove through Tifton, could have saved a bunch by dropping of the sewing machine to your brother)

Woodman, That is what I was thinking in a roundabout way. One code throwing another. In any case, two things do not make a problem. I will ask the maintenance guys when I get my next service. My Subaru dealer is pretty good about that.