• | 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 |
---|---|---|---|---|
Outside Air Temperature Sensor Signal | B0158 03 | B0158 07 | B0158 07 | -- |
Inside Air Temperature Sensor Signal | B0163 06 | B0163 06 | B0163 06 | -- |
Low Reference | -- | B0158 07, B0163 06 | -- | -- |
The HVAC control module monitors the air temperature sensors with a low reference circuit and 5-volt signal circuit. The HVAC control module monitors the voltage drop across the sensor, which is proportional to temperature. When the ambient air temperatures are cold, the resistance of the sensor is high and the voltage signals are high. When the ambient air temperatures are hot, the resistance of the sensors is 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 greater 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 driver information center (DIC) will display SERVICE A/C SYSTEM. |
• | The DTC will become history if the HVAC control module no longer detects a failure. |
• | The history DTC will clear after 50 fault-free ignition cycles. |
Automatic HVAC Description and Operation
Control Module References for scan tool information
Ignition ON, observe the appropriate air temperature sensor. The reading should be between -35°C (-39°F) and 85°C (185°F) and change with air temperature changes.
• | Ambient air temperature sensor terminal B |
• | Inside air temperature sensor terminal 1 |
⇒ | 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 listed below for a short to ground. If the circuit tests normal, replace the HVAC control module. |
• | Ambient air temperature sensor terminal A |
• | Inside air temperature sensor terminal 2 |
• | Ambient air temperature sensor signal circuit terminal A and low reference circuit terminal B |
• | Inside air temperature sensor signal circuit terminal 2 and low reference circuit terminal 1 |
⇒ | 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 |