Circuit/System Description

The outside air temperature sensor is a variable resistor interfaced to the body control module (BCM). The BCM provides the logic for reading the sensor, filtering the data and transmitting this information via the GM LAN Low Speed Bus to the instrument panel cluster (IPC) for display. The temperature is sent to the IPC in Degrees Celsius. The IPC is responsible for displaying the temperature and converting to Degrees Fahrenheit if necessary. Two GM LAN Low Speed Bus signals are ultimately generated. An un-filtered value and a filtered value for use by the IPC display. The BCM also provides the sensor out-of-range detection and compensates for engine temperature by utilizing vehicle speed and engine off time duration. The algorithm for all messages is executed at a rate of once every 1 second.