• | 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 |
---|---|---|---|---|
Driver Air Temperature Door Control A Circuit | B0408 61 | B0408 61 | -- | -- |
Driver Air Temperature Door Control B Circuit | B0408 61 | B0408 61 | -- | -- |
Driver Air Temperature Door Position Signal | B0408 61, B0408 02 | B0408 05 | B0408 61, B0408 02, B0408 05 | -- |
Driver Air Temperature 5-Volt Reference Circuit | B0408 61 | B0408 02, B0408 04 | B0408 02, B0408 04 | -- |
Driver Air Temperature Low Reference Circuit | -- | -- | -- | -- |
The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of an electric motor and a potentiometer. The module supplies a low reference and 5-volt reference source voltage to the potentiometer. The HVAC control module monitors the voltage drop across the potentiometer on the door position signal circuit. When the actuator shaft rotates, the voltage on the door position signal circuit changes. The HVAC control module supplies the actuator motor with a 12 volt control circuit and a ground control circuit. The HVAC module controls the direction of the actuator door by changing the polarity of the control circuits.
DTC B0408 is for the drivers air temperature actuator.
• | The ignition is ON. |
• | Ignition voltage is between 9-16 volts. |
• | The HVAC module is ON. |
The actual door position differs from the commanded door position by more than 4 counts or the HVAC control module detects the door position signal circuit is less than 7 counts or greater than 250 counts.
The control circuit is deactivated for the appropriate actuator.
• | The DTC becomes history when the HVAC control module no longer detects the condition that set the DTC. |
• | The history DTC will clear after 50 fault-free ignition cycles. |
• | The DTC can be cleared with a scan tool. |
⇒ | 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 less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module. |
⇒ | If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module. |
⇒ | If greater than the specified range, test the signal circuit terminal 9 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 the test lamp remains always ON or always OFF during either commands, test for an open, short to ground, or short to voltage on either control circuit. If the circuit tests normal, replace the HVAC control module. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for HVAC control module replacement, setup, and programming |