GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 TrailBlazer - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC B0229, B0414, B0424, B3761, or B3770

Circuit Description

The following DTCs are for the HVAC door actuators:

    • B0229 is for the recirculation actuator.
    • B0414 is for the left air temperature actuator.
    • B0424 is for the right air temperature actuator.
    • B3761 is for the defrost actuator.
    • B3770 is for the mode 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 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. The module converts the voltage value to a count value where 1 volt is approximately equal to 51 counts.

The HVAC control module calibrates the travel range of the HVAC door actuators when it is initially powered by the battery positive voltage circuit. During calibration, the module commands the actuators in each direction until door travel is stopped. The module stores the minimum door positions and the maximum door positions of each actuator into memory. The total travel range is calculated by subtracting the minimum door position from the maximum door position. The door actuators can be calibrated again with a scan tool.

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

Conditions for Setting the DTC

The DTC sets when one of the following conditions are present:

    • The actual door position value for the actuator is less than 5 counts.
    • The actual door position value for the actuator is greater than 250 counts.
    • The actuator fails calibration because the calculated travel range value is too great or too small.

Action Taken When the DTC Sets
    • If the DTC sets because the actual door position value is out of range, the HVAC control module will command the actuator to a default position.
    • If the DTC sets because the actuator failed a calibration, the HVAC control module will attempt to calibrate the motor in the next transition from OFF to RUN mode.

Conditions for Clearing the DTC
    • The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
    • The history DTC will clear after 100 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.
    • 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 a signal circuit of an actuator is short to ground and the resistance across the internal potentiometer is low, then this condition could cause a multiple DTC concern.

Test Description

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

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

    2.

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

    3.

  3. Tests for a short to voltage in the 5-volt reference circuit.

    4.

  4. Tests for a high resistance or for an open in the low reference circuit.

    5.

  5. This step tests for an open on the low reference circuit that is common to all of the actuators. Choose the easiest HVAC door actuator that set a DTC to start the diagnosis.

    6.

  6. 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

Values

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

Is DTC B1375 set as a current DTC?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

With a scan tool, observe the Heating and Air Conditioning DTC list.

Does the scan tool indicate that at least 2 of the following DTC B0229, B0414, B0424, B3761 and B3770 are set as current DTC?

--

Go to Step 10

Go to Step 4

4
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With the scan tool, observe the appropriate Door Actual parameter in the Heating and Air Conditioning data list.

Does the scan tool indicate that the appropriate Door Actual parameter is within the specified range?

5-250 counts

Go to Step 5

Go to Step 6

5
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the appropriate HVAC door actuator ON and OFF while observing the corresponding Door Actual parameter.

Does the scan tool indicate that the value of the appropriate Door Actual parameter changes?

--

Go to Diagnostic Aids

Go to Step 19

6
  1. Turn OFF the ignition.
  2. Disconnect the appropriate HVAC door actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the appropriate Door Actual parameter.

Does the scan tool indicate that the appropriate Door Actual parameter is less than the specified value?

5 counts

Go to Step 7

Go to Step 17

7

  1. Turn OFF the ignition.
  2. Connect a 3-ampere fused jumper between the 5-volt reference circuit and the appropriate door position signal circuit of the HVAC door actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the appropriate Door Actual parameter.

Does the scan tool indicate that the appropriate Door Actual parameter is greater than the specified value?

230 counts

Go to Step 8

Go to Step 15

8

  1. Disconnect the fused jumper.
  2. Measure the voltage between the 5-volt reference circuit and the low reference circuit of the HVAC door actuator.

Does the voltage measure less than the specified value?

5.5 V

Go to Step 9

Go to Step 14

9

  1. Turn OFF the ignition.
  2. Disconnect the negative battery cable.
  3. Measure the resistance from the low reference circuit of the HVAC door actuator to a good ground.

Does the resistance measure less than the specified value?

5 ohms

Go to Step 22

Go to Step 18

10

  1. Disconnect the most accessible affected HVAC door actuator.
  2. Probe the low reference circuit of the HVAC door actuator with a test lamp from battery positive voltage.

Does the test lamp illuminate?

--

Go to Step 11

Go to Step 18

11

  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the Heating and Air Conditioning DTC list.
  3. While observing DTC list, disconnect and connect the electrical connector for each affected HVAC door actuator.

Did the scan tool indicate that only one DTC was present when a HVAC door actuator was disconnected?

--

Go to Step 13

Go to Step 12

12

Test the 5-volt reference circuit of the appropriate HVAC door actuator for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 26

Go to Step 23

13

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

Did you find and correct the condition?

--

Go to Step 26

Go to Step 22

14

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

Did you find and correct the condition?

--

Go to Step 26

Go to Step 23

15

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

Did you find and correct the condition?

--

Go to Step 26

Go to Step 16

16

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

Did you find and correct the condition?

--

Go to Step 26

Go to Step 23

17

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

Did you find and correct the condition?

--

Go to Step 26

Go to Step 22

18

  1. Disconnect the HVAC control module.
  2. Test the low reference circuit of the appropriate HVAC door actuator for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 26

Go to Step 23

19
  1. Observe the appropriate HVAC door actuator drive shaft.
  2. Backprobe and monitor the voltage from the signal circuit of the air temperature door actuator to a good ground.
  3. Connect a 3 amp fused jumper wire between appropriate door control circuit at 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 at the HVAC control module.

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

--

Go to Step 23

Go to Step 20

20

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

Did you find and correct the condition?

--

Go to Step 26

Go to Step 21

21

Test the ignition 3 voltage circuit of the appropriate HVAC door actuator for an open or a high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 26

Go to Step 22

22

Inspect for poor connections at the harness connector of the appropriate HVAC door actuator. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 26

Go to Step 24

23

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 26

Go to Step 25

24

Important: Perform the calibration procedure for HVAC door actuators.

Replace the HVAC door actuator. Refer to the appropriate replacement procedure:

Did you complete the replacement?

--

Go to Step 26

--

25

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

Did you complete the replacement?

--

Go to Step 26

--

26
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle according to the Conditions for Running in the DTC, as specified in the supporting text.

Does the DTC set again?

--

Go to Step 3

System OK