• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Ambient Air Temperature Sensor Signal | B0159 | B0159 | B0159 | -- |
Inside Air Temperature Sensor | B0164 | B0164 | B0164 | -- |
Low Reference | -- | B0159, B0164 | B0159, B0164 | -- |
The ambient air temperature sensor allows the HVAC control module to monitor the temperature of the air surrounding the front of the vehicle. The inside air temperature sensor assembly allows the HVAC control module to monitor the temperature of the air inside the passenger compartment. 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 circuits. The HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. The HVAC control module also uses the ambient air temperature input to calculate the value of the ambient air temperature display. When the air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the air temperatures are hot, the resistances of the sensors are low and the voltage signals are low.
The ignition is turned ON.
• | The HVAC control module detects the sensor signal circuit is less than -35°C (-39°F). |
• | The HVAC control module detects the sensor signal circuit is more than 85°C (185°F) . |
The HVAC control module uses a default air temperature value for further automatic control calculations. The default values are not displayed on the scan tool.
• | The DTC will become history if the HVAC control module no longer detects a failure. |
• | The history DTC will clear after 100 fault-free ignition cycles. |
Control Module References for scan tool information
Ignition ON, observe the appropriate scan tool Air Temp. Sensor parameter. The reading should be between -35°C (-39°F) and 85°C (185°F) and change with air temperature changes.
Important: An instant OAT update must be performed by pressing the A/C and Recirc buttons at the same time before and after the system has been serviced to update the filtered ambient air temperature sensor.
⇒ | If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module. |
⇒ | If greater than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module. |
⇒ | If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module. |
⇒ | If not within the specified range, replace the sensor. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for HVAC control module replacement, setup, and programming |