Circuit Description

WARNING: This page is about a different car, the 2003 Buick Regal and 2003 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

The following DTCs are for the temperature sensors monitored by the HVAC control module:

B0332 - ambient air temperature sensor
B0333 - ambient air temperature sensor
B0337 - inside air temperature sensor
B0338 - inside air temperature sensor

The HVAC control module monitors the temperature sensors to maintain the comfort level inside of the vehicle. The temperature sensors are a 2 wire negative temperature co-efficient thermistor. The HVAC control module applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The HVAC control module provides the ground to the air temperature sensors through the low reference circuit. The HVAC control module monitors the voltage drop across the air temperature sensors and uses the inputs for automatic control calculations. When the air temperatures are cold, the resistance of the sensors are high and the voltage signals are high. When the air temperatures are hot, the resistance of the sensors are low and the voltage signals are low. The HVAC control module converts the voltage values to count values where 1 V is approximately equal to 51 counts.