That is the signal of a transmission fault, and a code is stored in the transmission ECU. Usually, but not always, the car would go into limb home mode where you have only 2 forward gears and one reverse and you have to manually shift gears. One of the faults is oil temperature too high, which I would say is coupled with your engine ECU error code. It is possible that the fault is actually the temperature sender, not the thermostat. I have heared of that problem on these cars. There are 2 senders, one for the temperature gauge and one for the ECU. However if both the engine and transmission ECUs show high temperature then it is probably the thermostat and not the senders. Hope this helps.