GM Service Manual Online
For 1990-2009 cars only

Step

Action

Values

Yes

No

1

  1. Turn ON the ignition.
  2. Observe the temperature indication screen of the controller.

Does the digit flash?

--

Go to Step 2

Go to Step 3

2

Run a self-diagnosis circuit check.

Does the display indicate a defect code?

--

Go to appropriate DTC table

--

3

  1. Turn ON the ignition.
  2. Measure the voltage between ground and terminal 2 of the blower motor.

Does the voltage measure within the specified value?

11-14 V

Go to Step 4

Go to Step 5

4

Measure the voltage between ground and terminal B12 at the ACT switch.

Does the voltage measure within the specified value?

11-14 V

Go to Step 6

Go to Step 12

5

Repair any problem found in terminal 2 at the blower motor circuit or ground G203.

Did you complete the repair?

--

System OK

--

6

Measure the resistance between the connector terminals on the blower motor.

Does the resistance measure equal to the specified value?

5 ohms

Go to Step 8

Go to Step 7

7

Replace the blower motor.

Did you complete the repair?

--

System OK

--

8

  1. Turn OFF the ignition.
  2. Using an ohmmeter, measure the resistance between terminal 1 of the blower motor and terminal 2 of the power transistor.

Does the resistance measure equal to the specified value?

0 ohms

Go to Step 10

Go to Step 9

9

Repair the circuit between terminal 1 of the blower motor and terminal 2 of the power transistor.

Did you complete the repair?

--

System OK

--

10

Measure the resistance between terminal 2 of the power transistor connector to ground

Does the resistance measure equal to the specified value?

0 ohms

Go to Step 11

Go to Step 12

11

  1. Trace the circuit from terminal 2 of the power transistor connector to ground G203.
  2. Repair any problem found in the circuit to ground G203.

Did you complete the repair?

--

System OK

--

12

Replace the ATC controller.

Did you complete the repair?

--

System OK

--