For 1990-2009 cars

### Circuit Description

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 potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The module supplies a 5-volt source voltage to the potentiometer on the 5-volt reference circuit. The module supplies ground to the potentiometer through the low reference circuit. 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.

• | Temperature control 1 Feedback circuit refers to the driver air temperature actuator

• | Temperature control 2 Feedback circuit refers to the passenger air temperature actuator

• | Temperature control 3 Feedback circuit refers to the rear air temperature actuator

• | Air flow control 3 Feedback circuit refers to the mode actuator

• | Air flow control 7 Feedback circuit refers to the recirc actuator.

• | Air flow control 10 Feedback circuit refers to the rear mode actuator

### DTC Descriptors

This diagnostic procedure supports the following DTCs:

• | DTC B0413 Temperature Control 1 Feedback Circuit

• | DTC B0423 Temperature Control 2 Feedback Circuit

• | DTC B0433 Temperature Control 3 Feedback Circuit

• | DTC B3761 Air Flow Control 3 Feedback Circuit

• | DTC B3773 Air Flow Control 7 Feedback Circuit

• | DTC B3782 Air Flow Control 10 Feedback Circuit

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description .

DTC Symptom | DTC Symptom Descriptor
--- | ---
00 | Out of Range Condition

### Conditions for Running the DTC

The ignition is ON.

### Conditions for Setting the DTC

The HVAC control module detects the door position signal circuit is less than 7 counts for more than 1 second or more than 250 counts.

### Action Taken When the DTC Sets

The HVAC control module uses only the minimum and maximum door positions.

### Conditions for Clearing the DTC

• | 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.

### Test Description

The number below refers to the step number on the diagnostic table.

1. This step verifies that the HVAC control module is able to command the appropriate HVAC actuator.

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 | Go to Diagnostic System Check - Vehicle
2 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. With a scan tool, command the appropriate actuator in both directions.

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
4 |

1. Turn OFF the ignition.
2. Disconnect the actuator connector.
3. Turn ON the ignition.
4. Turn ON the HVAC module.
5. Connect a test lamp between the two driver circuits.
6. Command the actuator in both directions.

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:

• | An open

• | A high resistance

• | A short to ground

• | A short to voltage

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:

• | A misaligned HVAC actuator

• | Broken or binding linkages or door

• | An obstruction that prevents the door from operating within its full range of motion

Did you find and correct the condition?

--

Go to Step 17

Go to Step 13

7 |

1. Turn OFF the ignition.
2. Unplug the appropriate actuator.
3. Turn ON the ignition.
4. Turn ON the HVAC control module.
5. Using a (DMM) measure the 5-volt reference.

Does the volt meter display near the specified value?

5V

Go to Step 8

Go to Step 12

8 | Using a DMM measure the signal circuit. Does the DMM display near the specified value? | 5V | 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? | 5V | Go to Step 13 | Go to Step 10
10 | Test the low reference circuit of the appropriate actuator for the following:

• | An open

• | A short to voltage

• | A high resistance

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:

• | An open

• | A high resistance

• | A short to ground

• | A short to voltage

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:

• | An open

• | A high resistance

• | A short to ground

• | A short to voltage

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:

• | Mode Actuator Replacement

• | Temperature Valve Actuator Replacement - Right Side

• | Temperature Valve Actuator Replacement - Left Side

• | Recirculation Actuator Replacement

• | Auxiliary Temperature Valve Actuator Replacement

• | Mode Actuator Replacement - Console

Have you finished 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. Have you finished the replacement? | -- | Go to Step 17 | --
17 |

1. Use the scan tool in order to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK