Circuit Description
The air temperature actuator is an electronic device that incorporates a stepper motor and a feedback potentiometer. The HVAC control module determines the position of the air temperature actuator from the voltage on the potentiometer. When the air temperature changes by greater than 4 counts, the control module performs the following functions:
| • | Drives the air temperature actuator in the appropriate direction in order to achieve the desired setting |
| • | Compares the actual position to the commanded position |
If the actual value differs from the commanded value by 4 or more counts, the actuator is stalled, and the DTC will set.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | Ignition voltage is between 9-16 volts. |
| • | An actuator change in position is attempted. |
Conditions for Setting the DTC
The actual position of the air mix door differs from the commanded position by at least 4 counts.
Action Taken When the DTC Sets
The actuator is stalled, and the HVAC control module will command the actuator to stop rotation.
Conditions for Clearing the DTC
| • | If the HVAC control no longer detects a condition, then the DTC will become history. |
| • | The history DTC will clear after 50 ignition cycles without a condition. |
| • | The DTC can be cleared with a scan tool. |
Diagnostic Aids
| • | A dead zone exists in a range 10 counts above the mix door maximum position to 10 counts below the mix door minimum position. When the air mix door actual data parameter is within the dead zone, the DTC will not set. If the commanded data parameter differs from the actual data parameter by 4 or more counts outside the dead zone, the DTC will set. |
| • | A damaged air temperature door, a damaged actuator, a broken air temperature door, or a broken actuator can cause this DTC to set. |
| • | If the condition is 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 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, B0429 and B03531 set along with B0408? | -- | Go to Step 3 | |||||||
Does the scan tool indicate that the Air Mix Door Commanded data parameter is within the specified value of the Air Mix Door Actual data parameter? | 0-3 Counts | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 4 | |||||||
4 |
Does the Air 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 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 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 air temperature door control circuit of the 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 air temperature actuator ground 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 air temperature actuator connector and the HVAC control module connector must be connected to correctly perform test.
Does the air temperature actuator drive shaft rotate and do the counts change? | -- | Go to Step 12 | Go to Step 10 | ||||||
10 | Inspect the air temperature door and the 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 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 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 |
Important:: Perform the recalibration procedure for the air temperature actuator. Replace the air temperature actuator. Refer to Air Temperature Actuator Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
14 |
Important:: Perform the recalibration procedure for the HVAC control module. Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- | ||||||
15 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||
