GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

  1. Turn the ignition switch off.
  2. Disconnect the generator connector.
  3. Turn the ignition switch on.
  4. Connect a scan tool to the Data Link Connector (DLC).
  5. On the scan tool, perform the following:
  6. 5.1. Select: Powertrain Control Module (PCM)
    5.2. Select: Special Functions.
    5.3. Select: Engine Output Controls.
    5.4. Select: GEN L Terminal.
    5.5. Command the generator ON.
  7. Using a DMM, measure the voltage between the generator harness connector terminal B and ground.

Is the measured voltage within the specified range?

5V

Go to Step 2

Go to Step 6

2

Using a DMM, measure the voltage between the generator BAT terminal and ground.

Is the voltage measured within the specified range?

9-14V

Go to Step 3

Go to Step 9

3

  1. Reconnect the generator connector.
  2. Turn all the accessories OFF.
  3. Run the engine at idle speed.
  4. Using DMM, measure the voltage across the battery terminals.

Is the voltage measured within the specified range?

13-16V

Go to Step 4

Go to Step 10

4

Load test the generator. Refer to Generator Not Operating Properly in Engine Electrical for service procedure.

Does the generator operate properly?

--

Go to Step 5

Go to Step 10

5

Replace the battery. Refer to Battery Replacement in Engine Electrical.

Is the repair complete?

--

Go to Charging System Check

--

6

Check for poor connection or open in circuit 225.

Is there a poor connection or open in circuit 225?

--

Go to Step 7

Go to Step 8

7

Repair the poor connection or open in circuit 225.

Is the repair complete?

--

Go to Charging System Check

--

8

The Powertrain Control Module (PCM) is not enabling circuit 225, thus disabling the generator. Refer to Powertrain Control Module Diagnosis in Engine Controls for further diagnosis and repair of the PCM.

Is the action complete?

--

Go to Charging System Check

--

9

Repair poor connection or open in circuit 2 or the fusible link to the generator BATT terminal.

Is the repair complete?

--

Go to Charging System Check

--

10

Replace the generator. Refer to Generator Replacement in Engine Electrical.

Is the repair complete?

--

Go to Charging System Check

--