Outside Air Temperature Display

The AAT sensor provides the AAT data used for the outside air temperature display in the IPC. The AAT sensor is hardwired to the PCM through separate input and return circuits. The PCM provides a reference voltage to the AAT sensor and monitors the change in voltage resulting from changes in resistance as determined by outside air temperature. The PCM filters the AAT input and sends the BCM the air ambient temperature filtered message over the HS-CAN. The BCM sends the air ambient temperature filtered message to the IPC over the MS-CAN.

Due to the location of the AAT sensor in the front grill area it is greatly influenced by heat generated from the engine compartment at low vehicle speeds and at engine idle. For this reason the outside air temperature value displayed in the IPC does not update in the upward (hotter) direction under 33 km/h (20 mph). This update strategy is used because the PCM is unable to determine whether the increase in temperature is truly from an ambient temperature rise or by heat generated from the engine compartment.

The outside air temperature display in the IPC updates in the upward (hotter) direction under either of the following situations:

if the vehicle is driven over 33 km/h (20 mph) continuously without the vehicle speed dropping below 33 km/h (20 mph) for approximately 90 seconds.
if the vehicle is allowed to sit with the engine off for approximately 6 hours (the outside air temperature display in the IPC immediately updates to reflect the current ambient conditions since the engine has cooled sufficiently and no longer has an effect on the outside air temperature sensor reading).

NOTE: If the vehicle speed drops below 33 km/h (20 mph) before the outside air temperature display in the IPC begins to update the PCM logic resets and the time starts over.

Because this filtering strategy exists, it may be necessary to drive the vehicle continuously above 33 km/h (20 mph) for approximately 90 seconds when observing the outside air temperature display operation. After the vehicle has been driven above 33 km/h (20 mph) for 90 seconds, the outside air temperature display in the IPC should start to filter upward toward the actual outside air temperature. Depending on the difference between what the outside air temperature is displaying in the IPC and the actual outside temperature it can take several minutes for the outside air temperature display in the IPC to reach the outside temp.

The outside air temperature display in the IPC does not filter in the downward (colder) direction and always displays the coldest temperature detected by the sensor even when the vehicle is stationary. When the outside AAT is lower than the temperature displayed in the IPC, the IPC immediately updates the displayed temperature downward to reflect the colder ambient air temperature, even at idle.