GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 SSR 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 DTC 001 or DTC 100

Circuit Description
    • DTC 001 is for the mode actuator.
    • DTC 100 is for the air temperature actuator.

The HVAC control module controls the HVAC door actuators to regulate the airflow through the HVAC system. Each actuator consists of a stepper motor, a logic circuit, and a potentiometer. The potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The logic circuit inside the actuators receives control signals from the HVAC control module and controls the internal stepper motor. When a door positional change is required, the HVAC control module calculates a commanded door position. The module compares the commanded door position to the actual door position and determines the needed direction of motor rotation. The module applies a signal voltage to the door control circuit that is an input to the internal logic circuit of the door actuator. A 5-volt signal increases the door position. A 0-volt signal decreases the door position. When the commanded door position is equal to the actual door position, the HVAC control module sends a 2.5-volt signal to the door actuator and motor rotation stops. The ignition 3 voltage circuit provides source voltage to the logic circuit. The module provides ground to the actuator logic circuit through the low reference circuit.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC 001 Mode Actuator Failure
    • DTC 100 Air Temperature Actuator Failure

Conditions for Running the DTC
    • Source voltage is 8.7-16.5 volts.
    • The ignition is ON.

Conditions for Setting the DTC

The actual door position is not near the commanded door position.

Action Taken When the DTC Sets

The HVAC control module does not command the actuator to move for the remainder of the ignition cycle.

Conditions for Clearing the DTC

The DTC Clearing is performed. Refer to Diagnostic Trouble Code (DTC) Clearing .

Diagnostic Aids
    • If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
    • If the DTC sets following a calibration of the door actuator, inspect the door and the actuator for the following conditions:
       - A misaligned actuator
       - Broken linkages or binding linkages
       - A broken door or a binding door
       - An obstruction that prevents the door from operating within the full range of motion
       - Missing seals to the door
       - Poor connections at the harness connector of the door actuator
    • If both DTCs are present, then there is a circuit failure or a HVAC door actuator is pulling the 5-volt reference circuit low.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The appropriate HVAC door actuator is the actuator that set the DTC. If both DTCs are present, then test the air temperature actuator. The air temperature actuator is easier to access.

    2.

  2. This step simulates the output of the HVAC control module to drive the appropriate HVAC door actuator clockwise or counter clockwise.

    3.

  3. Disconnecting each actuator, one at a time, isolates the disconnected actuators signal circuit from the 5-volt reference circuit that is common to all the actuators.

Step

Action

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 in Vehicle DTC Information

2

  1. Disconnect the appropriate HVAC door actuator.
  2. Connect a test lamp between ignition 3 voltage and the ground circuit of the appropriate HVAC door actuator.

Does the test lamp illuminate?

Go to Step 4

Go to Step 3

3

Connect a test lamp between ignition 3 voltage of the air temperature actuator and a good ground.

Does the test lamp illuminate?

Go to Step 13

Go to Step 14

4
  1. Disconnect the appropriate HVAC door actuator.
  2. Measure the voltage between the 5-volt reference circuit of the appropriate HVAC door actuator and a good ground.

Does the voltage measure near 5 volts?

Go to Step 5

Go to Step 8

5

Measure the voltage from the appropriate door control circuit of the appropriate HVAC door actuator to a good ground.

Does the voltage measure near 2.5 volts?

Go to Step 6

Go to Step 12

6

Measure the voltage from the appropriate door position signal circuit of the appropriate HVAC door actuator to a good ground.

Does the voltage measure near 5 volts?

Go to Step 7

Go to Step 11

7

  1. Connect the electrical connector of the appropriate HVAC door actuator.
  2. Observe the appropriate HVAC door actuator drive shaft.
  3. Connect a 3-amp fused jumper wire between the appropriate door control circuit of the HVAC control module and a good ground.
  4. Disconnect the fused jumper wire.
  5. Connect a 3-amp fused jumper wire between the appropriate door control circuit and the 5-volt reference circuit of the HVAC control module.

Does the drive shaft of the appropriate HVAC door actuator rotate?

Go to Step 16

Go to Step 9

8

  1. Measure the voltage of the 5-volt reference circuit at the HVAC control module.
  2. Disconnect the air temperature actuator.
  3. Connect the air temperature actuator.
  4. Disconnect the mode actuator.
  5. Connect the mode actuator.

Did the voltage return to the 5-volt range with an HVAC door actuator disconnected?

Go to Step 15

Go to Step 10

9

Inspect the appropriate HVAC door and the appropriate HVAC door actuator for the following conditions:

    • A misaligned HVAC door actuator--Refer to Air Temperature Actuator Replacement or Mode Actuator Replacement .
    • Broken linkages or binding linkages
    • A broken HVAC door or a binding HVAC door
    • An obstruction that prevents the HVAC door from operating within the full range of motion
    • Missing seals to the HVAC door
    • Misaligned seals to the HVAC door

Did you find and correct the condition?

Go to Step 19

Go to Step 15

10

Test the 5-volt reference circuit of the appropriate HVAC door actuator for a short to ground, short to voltage, an open, and a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 16

11

Test the appropriate HVAC door actuator position signal circuit of the appropriate HVAC door actuator for a short to ground, short to voltage, an open, and a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 16

12

Test the appropriate HVAC door actuator control circuit of the appropriate HVAC door actuator for the following conditions:

    • A short to ground
    • A short to voltage
    • An open
    • A high resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 16

13

Repair the ground circuit of the appropriate HVAC door actuator. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

14

Repair the ignition 3 voltage circuit of the appropriate HVAC door actuator. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 19

--

15

Inspect for poor connections at the harness connector of the appropriate HVAC door 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 19

Go to Step 17

16

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 19

Go to Step 18

17

Important: Perform the calibration procedure for the appropriate HVAC door actuator.

Replace the appropriate HVAC door actuator. Refer to Air Temperature Actuator Replacement or Mode Actuator Replacement .

Did you complete the replacement?

Go to Step 19

--

18

Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 19

--

19

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