"Ambient temperature damping
When the ambient temperature increases, the ATC
ECU imposes a rate of change limit of 0.5 °C (1 °F)
/minute. When the ambient temperature is decreasing,
the ATC ECU accepts an unlimited rate of change.
Ambient temperature input strategy (from VIN
381431)
The ATC ECU incorporates a software strategy to
overcome the effect of radiant heat from the engine
and cooling systems on the ambient temperature
sensor:
At vehicle speeds of 15 mph (24 km/h) and
above, the input is considered valid and
changes are accepted. The value of the
input is stored in memory and constantly
updated while the vehicle speed is above
15 mph (24 km/h).
At vehicle speeds below 15 mph (24 km/h),
changes of input are considered suspect
and changes are ignored. In place of the
actual input, the ATC ECU uses the value
stored in memory.
When the ignition is switched on, if the
ATC ECU detects warm heater coolant, it
uses the ambient temperature stored in
memory. If the ATC ECU detects cold
coolant, it uses the input from the ambient
temperature sensor."
I knew had seen some where...
But apart to trying to prove you guys wrong, not my intention as we all know the invaluable knowledge so many time shared by both of you, my point is when i start the car in "extreme" temperatures, cold or hot, it takes a while to get the correct reading.