B0178 GMC - Output Air Temperature Sensor 2 Circuit
- Faulty Output Air Temperature Sensor 2
- Output Air Temperature Sensor 2 harness is open or shorted
- Output Air Temperature Sensor 2 circuit poor electrical connection
- Faulty Heating, Ventilation, and Air Conditioning (HVAC) Control Module
Tech notesB0178 05: Output Air Temperature Sensor 2 Circuit Short to Battery or Open
B0178 02: Output Air Temperature Sensor 2 Circuit Short to Ground
- Engine Light ON (or Service Engine Soon Warning Light)
B0178 Gmc DescriptionAir temperature sensors allow the Heating, Ventilation, and Air Conditioning (HVAC) Control Module to monitor the temperature of the discharge air in the HVAC ducts. The module applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The module provides ground to the air temperature sensors through the low reference circuit. The HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. When the duct air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the duct air temperatures are hot, the resistances of the sensors are low and the voltage signals are low. The HVAC control module converts the voltage values to count values where 1 volt is approximately equal to 51 counts.
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