GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

Inspect the HVAC fuse in the underhood fuse block.

Is the HVAC fuse open?

--

Go to Step 3

Go to Step 6

3

  1. Disconnect the blower motor control module connector.
  2. Connect a J 39200 .
  3. Important: The load side of the fuse is the terminal without battery voltage and the ignition switch in RUN.

  4. Measure the resistance of the load side of the HVAC fuse to the battery ground.
  5. Leave the meter connected until the test is complete or until you are told to remove it.

Is the reading less than the specified value?

0.5 ohms

Go to Step 4

Go to Step 5

4

Repair the short to ground in CKT 540.

Is the repair complete?

--

Go to Diagnostic System Check

--

5

  1. Replace the HVAC fuse.
  2. Operate the blower motor.

Does the motor operate correctly?

--

Go to Diagnostic System Check

Go to Step 11

6

  1. Disconnect the blower motor control module connector.
  2. Connect a test lamp between the blower motor control module connector terminal A and terminal B.

Does the test lamp light?

--

Go to Step 7

Go to Step 8

7

  1. Connect the blower motor control module.
  2. Turn the ignition switch to the ON position.
  3. Set the electronic climate control (ECC) module to a midrange position.
  4. Connect a J 39200 .
  5. Backprobe the ECC module connector C16 to ground.

Is the reading within the specified range?

2-4 V

Go to Step 11

Go to Step 14

8

Connect a test lamp between the blower motor connector terminal B and the battery ground.

Does the test lamp light?

--

Go to Step 10

Go to Step 9

9

Repair an open in CKT 540.

Is the repair complete?

--

Go to Diagnostic System Check

--

10

Repair an open in CKT 850.

Is the repair complete?

--

Go to Diagnostic System Check

--

11

  1. Disconnect the blower motor connector and blower motor control module.
  2. Connect a jumper wire from the blower motor control module terminal B to the blower motor PPL terminal.
  3. Caution: The jumpers must be of adequate gauge in order to handle the blower motor current.

  4. Connect a jumper wire from the blower motor control module A to the blower motor BLK terminal.

Does the blower motor operate at maximum speed?

--

Go to Step 13

Go to Step 12

12

Replace the blower motor. Refer to Blower Motor and Fan Replacement .

Is the replacement complete?

--

Go to Diagnostic System Check

--

13

Replace the blower motor module. Refer to Blower Motor and Fan Replacement .

Is the replacement complete?

--

Go to Diagnostic System Check

--

14

Note the readings from the scan tool.

Is the reading equivalent to the specified value?

0 V

Go to Step 15

Go to Diagnostic System Check

15

  1. Turn the ignition to the OFF position.
  2. Disconnect the ECC module electrical connector.
  3. Disconnect the blower motor control module electrical connector.
  4. Connect a test lamp between the blower motor control module connector terminal B and terminal C.

Does the test lamp light?

--

Go to Step 16

Go to Diagnostic System Check

16

Repair a short to ground in CKT 760.

Is the repair complete?

--

Go to Diagnostic System Check

--

17

Connect a test lamp between the blower motor control module harness terminal A and terminal C.

Does the test lamp light?

--

Go to Step 18

Go to Step 19

18

Repair a short to battery in CKT 760.

Is the repair complete?

--

Go to Diagnostic System Check

--

19

Replace the blower motor control module. Refer to Blower Motor and Fan Replacement

Does the blower motor operate properly?

--

Go to Diagnostic System Check

Go to Step 20

20

Replace the ECC module. Refer to Control Assembly Replacement .

Is the replacement complete?

--

Go to Diagnostic System Check

--