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. When a change in air temperature is required (greater than 4 counts) the HVAC control module will drive the air temperature actuator in the appropriate direction to achieve the desired setting while comparing the actual position to the commanded position. If the actual value differs from the commanded value by 4 or more counts, the actuator is considered stalled and the DTC will set.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | Ignition voltage is between 9-16 volts. |
| • | An actuator positional change is attempted. |
Conditions for Setting the DTC
The actual air mix door position differs from the commanded air mix door position by 4 counts or more.
Action Taken When the DTC Sets
The actuator is considered stalled and the HVAC control module will command the actuator to stop rotation (2.5 V).
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
| • | A dead zone exists in a range 10 counts above or below the mix door max or mix door min positions. When the air mix door actual data parameter is within the dead zone, the DTC will not set. If the air mix door commanded data parameter differs from the air mix door actual data parameter by 4 counts or more outside the dead zone, the DTC will set. |
| • | A damaged or broken auxiliary air temperature door and or actuator can cause this DTC to set. |
| • | If condition not present refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step determines if the auxiliary air temperature door position is within the specified range of the commanded value.
-
Tests for a short to voltage in the 5 volt reference circuit.
Step | Action | Values | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Schematics | ||||||||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | |||||||
2 |
Does the scan tool indicate that DTC B0248, B0268, B0408 and B03531 set along with B0429? | -- | Go to Step 3 | |||||||
Does the scan tool indicate that the Aux. Mix Door Commanded data parameter is within the specified value of the Aux. Mix Door Actual data parameter? | 0-3 Counts | Go to Diagnostic Aids | Go to Step 4 | |||||||
4 |
Does the Aux. Mix Door Actual data parameter change at all? | -- | Go to Step 9 | Go to Step 5 | ||||||
5 | Test the ignition 3 voltage circuit of the auxiliary air temperature actuator for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 6 | ||||||
Test the 5 volt reference 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 15 | Go to Step 7 | |||||||
7 | Test the control 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 15 | Go to Step 8 | ||||||
8 | Test the ground circuit of the auxiliary air temperature actuator for open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 9 | ||||||
9 |
Important:: The auxiliary air temperature actuator connector and the auxiliary HVAC control module 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 12 | Go to Step 10 | ||||||
10 | 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 15 | Go to Step 11 | ||||||
11 | 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 15 | Go to Step 13 | ||||||
12 | Inspect for poor connections at the harness connector of the auxiliary HVAC control module. 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 15 | Go to Step 14 | ||||||
13 | Replace the auxiliary air temperature actuator. Refer to Auxiliary Temperature Valve Actuator Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
14 | Replace the auxiliary HVAC control module. Refer to Auxiliary Heater and Air Conditioning Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
15 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||
