Circuit Description
The auxiliary air temperature actuator is an electronic device that incorporates a stepper motor and feedback potentiometer. The position of the auxiliary air temperature actuator is based on the auxiliary air temperature door position signal voltage from the potentiometer. The rear auxiliary HVAC module converts this voltage to a digital signal that can be transmitted over the keyboard display driver (KDD) data bus to the HVAC control module. The HVAC control module contains the logic that controls the operation of the auxiliary air temperature actuator. Whenever the HVAC control modules keep alive memory battery power is interrupted, the HVAC control module will perform a recalibration of the actuators. The HVAC control module will perform a travel range comparison of the calculated minimum and maximum extremes of the actuator to the calibrated minimum and maximum range extremes within the HVAC control module. If the calculated range does not equal the calibrated expected range the actuator will be considered not calibrated and the DTC will set. The HVAC control module will also perform a continuous test on the current feedback value. If the feedback value does not equal or fall within the calibrated range the DTC will set.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | Ignition voltage is between 9-16 volts. |
| • | The HVAC control modules keep alive memory battery power must be interrupted to run the range check. |
Conditions for Setting the DTC
| • | The auxiliary air temperature door position signal is less than 5 counts or greater than 250 counts. |
| • | The auxiliary air temperature actuators total travel range (max-min) is less than or greater than the calibrated limits. |
Action Taken When the DTC Sets
| • | The HVAC control module will continue to make use of whatever travel range is still available. |
| • | Each time the ignition switch is turned ON the HVAC control module will recheck the actuator travel range. |
Conditions for Clearing the DTC
| • | If the HVAC control no longer detects a failure, then the DTC will become history. |
| • | The history DTC will clear after 50 ignition cycles without a failure. |
| • | The DTC can be cleared with a scan tool. |
Diagnostic Aids
| • | The range fault can only be detected following a check of the actuator travel range. The actuator travel range check can only be initiated by disrupting power to the HVAC control module. |
| • | The calibration limit is 64 to 216 counts. An actual range below this limit suggests an obstruction (something stuck in the door limiting travel). An actual range above this limit suggests an over travel condition (damaged or missing foam seals). |
| • | A damaged or broken auxiliary air temperature door and or actuator can cause this DTC to set. |
| • | If none of the above conditions exist refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Air Delivery/Temperature Control Schematics | ||||||||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check | ||||||
2 |
Does the result of the calculation indicate that the actual travel of the auxiliary air temperature actuator is within the specified range? | 64-216 counts | Go to Step 3 | Go to Step 8 | ||||||
3 |
Does the scan tool indicate that the Aux. Mix Door Actual data parameter is within the specified range? | 5-250 counts | Go to Diagnostic Aids | Go to Step 4 | ||||||
4 | Test the ground circuit of the auxiliary air temperature actuator for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 5 | ||||||
5 | Test the 5 volt reference circuit of the auxiliary air temperature actuator for a short to ground or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 6 | ||||||
6 | Test the auxiliary air temperature door position signal circuit of the auxiliary air temperature actuator for an open, high resistance, short to ground or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 7 | ||||||
7 |
Important: The auxiliary air temperature actuator connector and the HVAC control module - rear auxiliary connector must be connected to correctly perform test.
Does the auxiliary air temperature actuator drive shaft rotate and do the counts change? | -- | Go to Step 10 | Go to Step 9 | ||||||
8 | Inspect the auxiliary air temperature door and the auxiliary air temperature actuator for the following:
Did you find and correct the condition? | -- | Go to Step 13 | Go to Diagnostic Aids | ||||||
9 | Inspect for poor connections at the harness connector of the auxiliary air temperature actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||||
10 | Inspect for poor connections at the harness connector of the HVAC control module - rear auxiliary. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||||
11 | Replace the auxiliary air temperature actuator. Refer to Temperature Actuator Replacement - Auxiliary . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||
12 | Replace the HVAC control module - rear auxiliary. Refer to Control Assembly Replacement - Auxiliary . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||
13 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||
