External Temperature Display

WARNING: This page is about a different car, the 2014 Ford F-150. However, it is still accessible from the selected car via links, so may be relevant.

The ambient air temperature sensor is monitored by the PCM. The PCM sends the raw value through the HS-CAN to the BCM . The BCM sends the data through the MS-CAN to the HVAC module. The HVAC module filters and stabilizes the value and sends it back to the BCM . The BCM sends the filtered ambient temperature data to the IPC over the I-CAN . The IPC sends the data over the I-CAN to the FDIM to display the temperature.

While the actual external temperature can vary continuously, the value that is displayed updates at a specific rate depending on whether or not the engine is "hot" and whether or not the vehicle is moving.

When the external temperature is rising, the display updates slowly.

Updates (when the actual external temperature is higher than currently displayed value) is limited to 0.6°C (1°F) every 20 seconds while the vehicle is moving at greater than 32 km/h (20 mph) for more than 60 seconds or 0.6°C (1°F) every 20 minutes if the vehicle is not moving at this speed. This is to prevent the heat from the engine compartment from affecting the accuracy of the display.

When the external temperature is dropping, the display updates quickly.

Updates (when the actual external temperature is lower than currently displayed value) are limited to 0.6°C (1°F) every 2 seconds (regardless of vehicle speed). Consequently the display essentially follows the drop experienced by the external temperature thermistor.