GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 DTC 4

Circuit Description

This code will set if the output of the mix door indicator indicates that the door opening angle is out of range or does not change value when the door should be moving. This would indicate a short circuit or an open in the sensor or the associated wiring harness, a door motor that is not operating, or a malfunction of the automatic temperature controller (ATC).

Step

Action

Values

Yes

No

1
  1. Disconnect the I/P wiring harness connector from the air mix door (AMD) motor.
  2. Use an ohmmeter to measure the resistance between terminals 5 and 7 on the AMD motor.

Does the measured resistance indicate an open or a shorted condition?

--

Go to Step 4

Go to Step 2

2

Measure the resistance between terminals 2 and 3 on the AMD motor.

Is the resistance equal to the specified value?

3,000 ohms

Go to Step 3

Go to Step 4

3

Measure the resistance between terminals 6 and 2 and between terminals 6 and 3 on the AMD motor.

Do these resistances add to approximately the value measured between terminals 2 and 3?

3,000 ohms

Go to Step 5

Go to Step 4

4

Replace the air mix door (AMD) motor. Refer to Air Temperature Actuator Replacement .

Is the repair complete?

--

System OK

--

5

Inspect the connector terminals at the AMD motor and the wiring in the automatic temperature controller (ATC) harness.

Is there a condition with any terminal on either the harness connector or the motor connector or the wiring?

--

Go to Step 6

Go to Step 7

6

Repair the condition found with a connector terminal or the wiring, or replace the motor as required.

Is the repair complete?

--

System OK

--

7
  1. Remove the ATC controller from the instrument panel.
  2. Disconnect the harness connectors from the ATC controller.
  3. Examine the connector terminals on the harness connectors and the controller connectors and the harness wiring.

Is there a condition with any of these connectors or the wiring?

--

Go to Step 8

Go to Step 9

8

Repair the problem found with a connector terminal or wiring.

Is the repair complete?

--

System OK

--

9

Inspect continuity in the harness between the controller connectors and the AMD motor connector.

    • Controller terminal A2 to motor terminal 7
    • Controller terminal A8 to motor terminal 5
    • Controller terminal B6 to motor terminal 2
    • Controller terminal B5 to motor terminal 6
    • Controller terminal B4 to motor terminal 3

Does the continuity equal the specified value?

0 ohms

Go to Step 10

Go to Step 11

10

Repair the continuity problem.

Is the repair complete?

--

System OK

--

11
  1. Reconnect the AMD motor to the ATC harness.
  2. Reconnect the ATC harness connectors to the controller.
  3. Turn ON the ignition, with the engine OFF.
  4. Use backprobing for voltage measurements.
  5. Measure the voltage between ground and terminal B5 at the controller.

Is the voltage less than the specified value?

4 V

Go to Step 12

Go to Step 14

12
  1. Set the temperature controller to 18°C (64°F).
  2. Connect a voltmeter between ground and terminal A8 at the controller. It should display about 12 volts.
  3. Raise the temperature setting on the controller to 32°C (90°F).

Does the voltage drop within the specified range?

12-0 V

Go to Step 13

Go to Step 15

13
  1. Connect a voltmeter between ground and terminal A2 at the controller. It should display about 12 volts.
  2. Change the temperature setting to 18°C (64°F).

Does the voltage drop within the specified range?

12-0 V

Go to Step 20

Go to Step 15

14
  1. Recheck the wiring harness and the connector terminals associated with controller terminals B4, B5, and B6, and AMD motor terminals 2, 6, and 3.
  2. Repair any problem found.

Is the repair complete?

--

System OK

--

15

Inspect all wiring circuits between the controller and the AMD motor.

Is there a problem in the wiring or the connectors?

--

Go to Step 16

Go to Step 17

16

Repair the problem in the wiring between the ATC and the AMD motor.

Is the repair complete?

--

System OK

--

17

Inspect the AMD motor.

Is there a problem in the AMD motor?

--

Go to Step 18

Go to Step 19

18

Replace the AMD motor. Refer to Air Temperature Actuator Replacement .

Is the repair complete?

--

System OK

--

19

Replace the controller. Refer to Heater and Air Conditioning Control Replacement .

Is the repair complete?

--

System OK

--

20

Observe the operation of the air mix door when the temperature setting is changed.

Does the door move normally?

--

Go to Step 22

Go to Step 21

21

Repair or replace the air mix door.

Is the repair complete?

--

System OK

--

22

Observe the operation of the AMD motor when the temperature setting is changed.

Does the motor operate normally?

--

Go to Step 23

Go to Step 18

23

Reconnect everything and test the system.

Does code 4 reset?

--

Go to Step 19

System OK