GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The HVAC control module receives a right air temperature actuator position signal from the right air temperature actuator. The right air temperature actuator position sensor is a potentiometer that is tied to a 5 volt reference source. The variable output from the potentiometer feeds back a position signal to a pull-up resistor located in the HVAC control module. This signal is used to determine the necessary drive signal to the right air temperature actuator motor to provide the proper air mix door position. This value is stored in the Keep Alive Memory (KAM) portion of the HVAC control module.

Conditions for Running DTC

The ignition is in the ON position.

Conditions for Setting the DTC

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

Install a scan tool to the diagnostic link connector. Turn the ignition switch to the ON position. Select the OUTPUT CONTROL screen in HVAC special functions. Use the MISCELLANEOUS TEST screen to manually drive the right air temperature actuator with the scan tool from fully open to fully closed. Monitor the RH MIX MTR POSITION FEE with the scan tool when this is done. A normal position feedback signal should range between 0-255 counts as the electric actuator is being moved.

If condition not present refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The number(s) below refer to the step number(s) 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. Tests for the proper operation of the circuit in the high voltage range.

  3. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

  4. Tests for a short to ground in the 5 volt reference circuit.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

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 RH Mix Mtr Position Fee parameter in the Heating and Air Conditioning data list.

Does the scan tool indicate that the RH Mix Mtr Position Fee 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 RH Mix Mtr Position Fee parameter is near the specified value?

128 Counts

Go to Step 5

Go to Step 4

4

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

Does the scan tool indicate that the RH Mix Mtr Position Fee 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 right 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 of the right air temperature actuator for a 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 7

7

Test the air temperature door position signal circuit of right 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 RH Mix Mtr Position Fee 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 right 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 right air temperature actuator. This drives the actuator to the full HOT position.

Does the left 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 right 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 right 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 13

Go to Step 12

11

Inspect for poor connections at the harness connector of 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

Important::  Perform the recalibration for the air temperature actuator.

Replace the left air temperature actuator. Refer to Air Temperature Actuator Replacement - Right Side

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