GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2003 🢒 Century 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B0361 or B0365

Circuit Description

The following DTCs are for the HVAC door actuators:

    • B0361 - left air temperature actuator
    • B0365 - right air temperature actuator

The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator is a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Ignition 3 voltage, low reference, control, 5 volt reference and position signal circuits enable the actuator to operate. The control circuit uses either a 0, 2.5 or 5 volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5 volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts. The HVAC control module converts the voltage values to count values where 1 V is approximately equal to 51 counts. The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted, value, the control signal is changed to either 0 or 5 volts depending upon the direction that the actuator needs to rotate to reach the commanded value. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module changes the control signal to 2.5 volts.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The air temperature door position signal circuit stays at or near 0 volts.

Action Taken When the DTC Sets

No driver warning message will be displayed for this DTC.

Conditions for Clearing the DTC
    • The DTC will become history if the HVAC control module no longer detects a failure.
    • The history DTC will clear after 50 fault-free ignition cycles.
    • The DTC can be cleared with a scan tool.

Diagnostic Aids

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.

  1. This step checks for a default action by the actuator. The actuator will default to 128 counts if the air temperature door position circuit is open, shorted to ground, or shorted to voltage. It will also default to this value if the low reference circuit or the 5 volt reference circuit is open.

    2.

  2. Tests for the air temperature actuator operating within its specified range.

    3.

  3. Tests the air temperature actuator ground circuit for an open.

    4.

  4. Tests the air temperature actuator 5 volt reference circuit for a short to ground, short to voltage, or an open.

  1. Tests the air temperature door position signal circuit for an open, high resistance, short to ground, or short to voltage.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the appropriate Mix Mtr Position Feedback parameter in the Heating and Air Conditioning data list.

Does the scan tool indicate that the appropriate Mix Mtr Position Feedback parameter is within the specified range?

1-3 Counts

Go to Step 9

Go to Step 3

3

Does the scan tool indicate that the appropriate Mix Mtr Position Feedback parameter is near the specified value?

128 Counts

Go to Step 5

Go to Step 4

4

  1. With the scan tool, command the appropriate air temperature actuator from OFF to ON.
  2. With the scan tool, observe the appropriate Mix Mtr Position Feedback parameter in the Heating and Air Conditioning data list.

Does the scan tool indicate that the appropriate Mix Mtr Position Feedback parameter is within the specified range?

3-252 Counts

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 5

5

Test the ground circuit of the appropriate 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 6

6

Test the 5 volt reference circuit for a short to ground, short to voltage, or 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 7

7

Test the air temperature door position signal circuit of the appropriate 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 8

8

Important: : The air temperature actuator connector and the HVAC control module connector must be connected to correctly perform the test.

  1. Turn ON the ignition, with the engine OFF.
  2. With the scan tool, observe the appropriate Mix Mtr Position Feedback parameter in the Heating and Air Conditioning data list.
  3. Connect a 3-amp fused jumper wire between the air temperature actuator door control circuit and the 5 volt reference circuit of the appropriate air temperature actuator. This drives the actuator to the full COOL position.
  4. Remove and reconnect the jumper wire between the air temperature actuator door control circuit and the ground circuit of the air temperature actuator. This drives the actuator to the full HOT position.

Does the air temperature actuator drive shaft rotate and do the counts change?

--

Go to Step 13

Go to Step 9

9

Inspect the air temperature door and the appropriate air temperature actuator for the following:

    • Incorrectly installed air temperature actuator.
    • Broken or binding linkages or air temperature door.
    • Obstruction that prevents the air temperature door from operating within its full range of motion.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

10

Inspect for poor connections at the harness connector of the appropriate 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 12

11

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 13

Go to Step 12

12

Replace the appropriate air temperature actuator. Refer to the following:

Did you complete the replacement?

--

Go to Step 13

--

13
  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