GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Bonneville 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 DTC B0238

Circuit Description

The mode actuator is an electronic stepper motor without a feedback circuit. It responds to voltage inputs from the HVAC control module with precalibrated non-adjustable position settings. The HVAC control module adjusts the mode actuator position to direct airflow from the outlets selected by the vehicle occupants.

Conditions for Running the DTC
    • The ignition is turned ON.
    • DTC B1327 must not be current.

Conditions for Setting the DTC

The mode door control circuit is shorted to ground or shorted to battery voltage for more than 2 seconds.

Action Taken When the DTC Sets

Control of the mode door position will be disabled.

Conditions for Clearing the DTC
    • The DTC will become history if the HVAC control module no longer detects a failure.
    • A history DTC will clear after 50 malfunction free ignition cycles
    • The HVAC control module receives the clear code command from the scan tool.

Test Description

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

  1. The mode actuator can be driven to one of two positions using the Defrost and A/C command keys on the scan tool. The scan tool displays module output as a percentage of maximum control voltage. It does not indicate true actuator or door position.

  2. This step verifies that the actuator is receiving the control voltage.

Step

Action

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 - Manual

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the mode actuator to DEFROST and to A/C.
  4. Observe the mode door actuator.

Does the drive shaft of the mode door actuator rotate?

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

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the mode actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the mode door control circuit of the mode actuator to a good ground.
  5. With a scan tool, command the mode actuator to DEFROST and to A/C.

Does the voltage change?

Go to Step 5

Go to Step 4

4

Test the mode door control circuit of the mode actuator for a short to ground and a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 6

5

Inspect for poor connections at the harness connector of the mode 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 9

Go to Step 7

6

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 9

Go to Step 8

7

Replace the mode actuator. Refer to Mode Actuator Replacement .

Did you complete the replacement?

Go to Step 9

--

8

Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

Go to Step 9

--

9
  1. Use a 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