Is there a link
Ran it low on AT oil.
At idle the engine doesn't produce enough power to overheat the transmission, especially if it's idling in Neutral - it can idle all day long with no effect on the transmission.
If it's in gear, stationary and being held on the brake with the engine above idle, there will be some "churning" of the fluid which will result in a heat build up, but you would have to be really ridiculous to get it to overheat - ridiculous as in half throttle or more whilst holding it on the brake.
Of course all of the above assumes that the OE transmission cooler in the bottom of the radiator is functional.
I pulled up anf the 'N' light was flashing - over hot AT fluid the book says - so I checked the dippy sticky and fluid level was right at the bottom. God knows how long it has been running so low though I checked it a few months back when I first had it I might have misread the dippy sticky. Fortunately I only use it for short runs (about 1.5 miles).
I have not detected an AT leak but there is a small crank leak. Maybe it is an AT leak and not the crank.
Link
There are two different flash rates, a slow flash & a fast flash - one acts as a TCU "check light" to alert you that the transmission controller has detected a fault, and the other is an "over temp" alert.
When I checked the book the flash rate was that of the overheating. After it had sttod for a while, long enough to cool, the flashing stopped. Since putting AT oil into it the flashing has not returned.
I wondered if low AT fluid could in any way affect the ECU and alter the idle speed.
Not that I'm aware of
I wondered if low AT fluid could in any way affect the ECU and alter the idle speed.
As far as I'm aware the TCU does not sense fluid level and there is no communication from the TCU to the ECU, although TPS data is sent to the TCU.
Theoretically low fluid can cause aeriation of the fluid and that can cause the load presented by the transmission to vary - that load would not be signficant at idle, or the engine would stall.
Convoluted
I wondered if low AT fluid could in any way affect the ECU and alter the idle speed.
As far as I'm aware the TCU does not sense fluid level and there is no communication from the TCU to the ECU, although TPS data is sent to the TCU.
Theoretically low fluid can cause aeriation of the fluid and that can cause the load presented by the transmission to vary - that load would not be signficant at idle, or the engine would stall.
Right, I think I follow that. It will be interesting to see what happens over the next few days now the tranny has oil. 
Syndicate
Not that I'm aware of...
At idle the engine doesn't produce enough power to overheat the transmission, especially if it's idling in Neutral - it can idle all day long with no effect on the transmission.
If it's in gear, stationary and being held on the brake with the engine above idle, there will be some "churning" of the fluid which will result in a heat build up, but you would have to be really ridiculous to get it to overheat - ridiculous as in half throttle or more whilst holding it on the brake.
Of course all of the above assumes that the OE transmission cooler in the bottom of the radiator is functional.