GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Inspect the ignition (IGN) 1 fuse.

Is the ignition (IGN) 1 fuse open?

--

Go to Step 2

Go to Step 3

2

Repair the short to ground in CKT 39.

Is the repair complete?

--

Go to Charging System Check

--

3

  1. Disconnect the generator connector.
  2. Turn the ignition switch to the RUN position.
  3. Attach a scan tool to the data link connector (DLC).
  4. Clear any diagnostic trouble codes (DTCs).
  5. Select MISC TESTS, ENG OUTPUTS, and GEN L TERM.
  6. Command the generator ON.
  7. Measure the voltage from the generator connector terminal B to ground.

Is the voltage equal to the specified value?

5V

Go to Step 4

Go to Step 9

4

Measure the voltage from the generator battery (Bat) terminal to ground.

Is the voltage equal to the specified value?

9-14V

Go to Step 5

Go to Step 12

5

  1. Reconnect the generator connector.
  2. Ensure that all of the accessories are OFF.
  3. Run the engine at a fast idle.
  4. Measure the voltage across the battery.

Is the voltage equal to the specified value?

13-16V

Go to Step 6

Go to Step 8

6

Load test the generator. Generator Assembly Check

Did the generator test OK?

--

Go to Step 7

Go to Step 8

7

Replace the battery. Refer to Battery Replacement.

Is the repair complete?

--

Go to Charging System Check

--

8

  1. Check for poor connections at the generator.
  2. If connections are ok, replace the generator. Refer to Generator Replacement .

Is the repair complete?

--

Go to Charging System Check

--

9

Inspect for a poor connection or an open in CKT 225.

Is there a poor connection or an open in CKT 225?

--

Go to Step 10

Go to Step 11

10

Repair the poor connection or the open in CKT 225.

Is the repair complete?

--

Go to Charging System Check

--

11

Replace the powertrain control module (PCM). Powertrain Control Module Replacement/Programming

Is the repair complete?

--

Go to Charging System Check

--

12

Repair one of the following conditions:

    • The open in CKT 2
    • The fusible link to the generator battery (Bat) terminal

Is the repair complete?

--

Go to Charging System Check

--