Circuit Description
The HVAC door actuator is an electronic motor with a feedback potentiometer. The HVAC control module supplies power and ground to the actuator. The HVAC control module controls the direction of the actuator by changing the polarity of the control circuit. When the actuator reaches the desired position, voltage is removed from the control circuit. The HVAC control module determines the current position of the actuator by monitoring the feedback voltage of the door position signal circuit. The feedback potentiometer position is a function of the actuator position.
| • | Air flow position command circuit range refers to the mode actuator. |
| • | Temperature control 1 circuit range refers to the driver air temperature actuator. |
| • | Temperature control 2 circuit range refers to the passenger air temperature actuator. |
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B0126 Air Flow Position Command Circuit Range |
| • | DTC B0409 Temperature Control 1 Circuit Range |
| • | DTC B0419 Temperature Control 2 Circuit Range |
Conditions for Running the DTC
| • | The ignition is ON. |
| • | Ignition voltage is between 9-16 volts. |
Conditions for Setting the DTC
The actual door position differs from the commanded door position by 4 counts or greater for more than 16 seconds.
Action Taken When the DTC Sets
The HVAC control module will not command actuator movement past the point where the stall condition is detected and will continue to make use of the remaining nonrestricted range.
Conditions for Clearing the DTC
| • | The DTC will become history if 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. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||
2 |
Does the actual parameter of the appropriate actuator change? | -- | Go to Step 3 | Go to Step 4 | ||||||||
3 | Is the voltage difference between the actual parameter and the commanded parameter of the appropriate actuator less than the specified value? | 0.3 V | Go to Step 7 | Go to Step 6 | ||||||||
Does the test lamp illuminate then turn OFF in both directions? | -- | Go to Step 13 | Go to Step 5 | |||||||||
5 | Test the control A circuit and control B circuit of the appropriate actuator for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15 | ||||||||
6 | Inspect the appropriate HVAC door and appropriate HVAC actuator for the following conditions:
Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 13 | ||||||||
7 |
Does the volt meter display near the specified value? | 5 V | Go to Step 8 | Go to Step 12 | ||||||||
8 | Using a DMM measure the signal circuit. Does the DMM display near the specified value? | 5 V | Go to Step 9 | Go to Step 11 | ||||||||
9 | Connect a DMM between the 5-volt reference circuit and the low reference circuit. Does the DMM display near the specified value? | 5 V | Go to Step 13 | Go to Step 10 | ||||||||
10 | Test the low reference circuit of the appropriate actuator for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15 | ||||||||
11 | Test the signal circuit of the appropriate actuator for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15 | ||||||||
12 | Test the 5-volt reference circuit of the appropriate actuator for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 15 | ||||||||
13 | Inspect for poor connections at the harness connector of the appropriate HVAC actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 | ||||||||
14 | Replace the appropriate HVAC actuator. Refer to the appropriate replacement procedure: Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||||
15 | 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 . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 | ||||||||
16 | Replace the appropriate HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||||
17 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||||
