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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 TrailBlazer - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 DTC B0145, B0428, or B3531

Circuit Description

The following DTCs are for the auxiliary HVAC door actuators:

    • B0145 is for the auxiliary mode actuator.
    • B0428 is for the auxiliary air temperature actuator.
    • B3531 is for the auxiliary console mode actuator.

The auxiliary HVAC actuators are a 5 wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and two control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The auxiliary HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 volts. This signal then is converted into a count value where as 1-volt will equal 51 counts.

The auxiliary 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.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC B0145 Air Flow Position Command 3 Circuit
    • DTC B0428 Temperature Control 3 Circuit
    • DTC B3531 Air Flow Control 10 Circuit Outside Air Temperature Sensor Circuit

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 for 2 minutes:

    • 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 actual door position is not near the commanded door position.
    • An auxiliary door actuator door position change request is made.

Action Taken When the DTC Sets

The auxiliary HVAC control module will attempt to position the actuator to its default position. They are as follows:

    • B0145 defaults the auxiliary mode actuator to the floor position.
    • B0428 defaults the auxiliary air temperature actuator to the full hot position.
    • B3531 defaults the console mode actuator to the floor position.

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 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

Test Description

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

  1. If more than one DTC is set, observe all of the Door Actual parameters for each corresponding DTC. If the door actual parameter is not out of range, then the concern is with the control portion of the actuator.

  2. The purpose of this step is to try to determine which actuator is internally shorted or if the auxiliary HVAC control module is creating the fault. After DTC are cleared, it can take up to 4 minutes for DTC to set.

    3.

  3. After DTC are cleared, it can take up to 4 minutes for DTC to set. The purpose of this step is to try to determine which actuator is internally shorted or if the auxiliary HVAC control module is creating the fault. If both DTCs return the auxiliary control module is internally shorted.

    4.

  4. The purpose of this step is to try to determine which actuator is internally shorted or if the auxiliary HVAC control module is creating the fault. After DTC are cleared, it can take up to 4 minutes for DTC to set.

    5.

  5. After DTC are cleared, it can take up to 4 minutes for DTC to set. The purpose of this step is to try to determine which actuator is internally shorted or if the auxiliary HVAC control module is creating the fault. If both DTCs return the auxiliary HVAC control module is internally shorted.

    6.

  6. If the scan tool does not display all three DTC, then the answer is No.

    7.

  7. If the scan tool does not display both DTC, then the answer is No.

    8.

  8. If the fused jumper opens, then the appropriate signal circuit is shorted to a power.

    9.

  9. If the scan tool parameter reads lower than 5 counts then the appropriate signal circuit is shorted to a ground.

    10.

  10. This step tests the 5-volt reference circuit. Test can be done with any auxiliary actuator. The auxiliary air temperature actuator can be accessed the quickest.

    11.

  11. If the scan tool displays one DTC when an actuator is disconnected, then the actuator that was disconnected is the area of the fault.

    12.

  12. The procedure for both auxiliary mode actuators are within the same replacement procedure.

    13.

  13. After a circuit repair, a recalibration of the actuators must be performed to ensure proper performance from the auxiliary HVAC system.

Step

Action

Values

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. 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 Rear HVAC/rear seat audio (RSA) data list.

Is the parameter within the calibrated range value?

20-235 counts

Go to Step 3

Go to Step 14

3

With the scan tool, observe the Rear HVAC/RSA DTCs.

Does the scan tool indicate that only one of the following DTCs are present B0145, B0428, B3531?

--

Go to Step 12

Go to Step 4

4

Does the scan tool indicate that DTCs B0145 and B3531 are set?

--

Go to Step 9

Go to Step 5

5

Does the scan tool indicate that DTCs B0145 and B0428 are set?

--

Go to Step 6

Go to Diagnostic Aids

6

Test the auxiliary actuator door control circuit of the auxiliary HVAC actuators for one of the following conditions:

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

Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 30

Go to Step 7

7

  1. With the scan tool, clear all DTCs.
  2. Disconnect the auxiliary air temperature actuator.
  3. Wait 4 minutes for DTC to set.
  4. With the scan tool, observe the Rear HVAC/RSA DTCs.

Does DTC B0145 return along with B0428?

--

Go to Step 8

Go to Step 27

8

  1. Reconnect the auxiliary air temperature actuator.
  2. With the scan tool, clear all DTCs.
  3. Disconnect the auxiliary mode actuator.
  4. Wait 4 minutes for DTC to set.
  5. With the scan tool, observe the Rear HVAC/RSA DTCs.

Does DTC B0428 return along with B0145?

--

Go to Step 26

Go to Step 27

9

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

Did you find and correct the condition?

--

Go to Step 30

Go to Step 10

10

  1. With the scan tool, clear all DTCs.
  2. Disconnect the auxiliary mode actuator.
  3. Wait 4 minutes for DTC to set.
  4. With the scan tool, observe the Rear HVAC/RSA DTCs.

Does DTC B3531 return along with B0145?

--

Go to Step 11

Go to Step 27

11

  1. Reconnect the auxiliary mode actuator.
  2. With the scan tool, clear all DTCs.
  3. Disconnect the auxiliary console actuator.
  4. Wait 4 minutes for DTC to set.
  5. With the scan tool, observe the Rear HVAC/RSA DTCs.

Does DTC B0145 return along with B3531?

--

Go to Step 26

Go to Step 27

12

Test the appropriate circuits for the DTC.

    • B0145 test the following circuits:
       - The auxiliary mode door control circuit for an open between the splice and auxiliary mode actuator
       - The auxiliary actuator door control circuit for an open between the splice and auxiliary mode actuator
       - The 5-volt reference circuit for an open between the splice and auxiliary mode actuator
    • B0428 test the following circuits:
       - The auxiliary air temperature door control circuit for an open, short to ground or short to voltage
       - The auxiliary actuator door control circuit for an open between the splice and the auxiliary air temperature actuator
    • B3531 test the following circuits:
       - The console mode door control circuit for an open, short to ground or short to voltage
       - The auxiliary mode door control circuit for an open between the splice and the console mode actuator

Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 30

Go to Step 13

13

  1. Change the appropriate auxiliary switch position.
  2. With the scan tool, observe the Commanded Door position for the appropriate actuator.

Does the commanded position change with each selection?

--

Go to Step 27

Go to Step 26

14

With a scan tool, observe the Rear HVAC/RSA DTC List.

Does the scan tool display B0145, B0428 and B3531?

--

Go to Step 20

Go to Step 15

15

Does the scan tool display B0145 and B0428?

--

Go to Step 20

Go to Step 16

16

  1. Disconnect the appropriate auxiliary actuator.
  2. Measure the voltage of the 5-volt reference circuit of the appropriate actuator to a good ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Does the voltage measure near 5 volts?

--

Go to Step 17

Go to Step 21

17

  1. Disconnect the appropriate auxiliary actuator.
  2. Measure the voltage of the 5-volt reference circuit to the low reference circuit of the appropriate auxiliary actuator. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Does the voltage measure near 5 volts?

--

Go to Step 18

Go to Step 24

18

  1. Connect a 3-amp fused jumper between the low reference circuit and the signal circuit of the appropriate auxiliary actuator.
  2. With a scan tool, observe the appropriate Door Actual parameter in the Rear HVAC/RSA data list.

Does the scan tool indicate that the appropriate Door Actual parameter is near 0 counts?

--

Go to Step 19

Go to Step 25

19

Disconnect the appropriate auxiliary actuator.

Does the scan tool indicate that the appropriate Door Actual parameter is over 245 counts?

--

Go to Step 27

Go to Step 25

20

Important: Ensure that the auxiliary air temperature actuator connector is connected during this step in order to avoid misdiagnosis. Test can be done with any auxiliary actuator. The auxiliary air temperature actuator can be accessed the quickest.

Measure the 5-volt reference circuit at the auxiliary air temperature actuator to a good ground. Refer to Circuit Testing in Wiring Systems.

Does voltage measure near 5 volts?

--

Go to Step 23

Go to Step 21

21

Test the 5-volt reference circuit of the auxiliary HVAC actuators for one of the following conditions:

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

Refer to Circuit Testing in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 30

Go to Step 22

22

Important: Each actuator must be disconnected and connected one at a time to ensure misdiagnosis does not occur.

  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the Rear HVAC/RSA DTC List.
  3. Disconnect each auxiliary HVAC actuator one at a time.

Does the scan tool display B0145, B0428 and B3531?

--

Go to Step 26

Go to Step 27

23

Connect a test lamp between the battery positive voltage circuit of the auxiliary HVAC control module and the low reference circuit of the auxiliary air temperature actuator.

Does the test lamp illuminate?

--

Go to Step 26

Go to Step 24

24

Test the low reference circuit of the auxiliary HVAC actuators for a high resistance or an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 30

Go to Step 26

25

Test the appropriate signal circuit of the auxiliary HVAC actuators for the following conditions:

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

Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 30

Go to Step 26

26

Inspect for poor connections at the harness connector of the auxiliary 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 30

Go to Step 29

27

Inspect for poor connections at the harness connector of the appropriate auxiliary HVAC 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 30

Go to Step 28

28

Replace the appropriate auxiliary HVAC actuator. Refer to the following:

Did you complete the replacement?

--

Go to Step 30

--

29

Replace the auxiliary 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 31

--

30

Recalibrate the actuators. Refer to Actuator Recalibration .

Did you complete the procedure?

--

Go to Step 31

--

31

Important: Ensure to test system for 2 minutes after clearing DTC to avoid misdiagnosis.

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC.

Does the DTC reset?

--

System OK

Go to Step 2