GM Service Manual Online
For 1990-2009 cars only

Battery Is Undercharged or Overcharged LP4/L21

Battery is Undercharged or Overcharged (Gasoline Engine)

Step

Action

Value(s)

Yes

No

1

  1. Disconnect the generator connector.
  2. Place the ignition switch in the RUN position.
  3. Connect a J 39200 DMM from CKT 25 (BRN) at the generator connector to the chassis ground.
  4. Observe the voltage reading on the J 39200 .

Is voltage present?

--

Go to Step 2

Go to Step 4

2

  1. Connect a DMM J 39200 from battery terminal CKT 1 (RED) at the generator connector to the chassis ground.
  2. Observe the voltage reading on the J 39200 .

Is voltage present?

--

Go to Step 3

Go to Step 5

3

  1. Reconnect the generator connector.
  2. Turn the accessories off.
  3. Run the engine at a fast idle.
  4. Connect a DMM J 39200 from battery terminal CKT 1 (RED) at the generator to the chassis ground.
  5. Observe the voltage reading on the J 39200 .

Does the voltage measure within the specified range?

13-16 V

Go to Step 6

Go to Step 7

4

Inspect the condition of the indicator bulb.

Is the indicator bulb in the proper condition?

--

Go to Step 8

Go to Step 9

5

Locate and repair the open in CKT 1 (RED) between the generator and the starter solenoid.

Is the repair complete?

--

System OK

--

6

Perform the battery load test. Refer to Charging System Check .

Is the testing complete?

--

System OK

--

7

Perform the generator bench test. Refer to Generator Not Operating Properly .

Does the generator meet the test requirements?

--

Go to Step 10

Go to Step 11

8

Locate and repair the open in CKT 25 (BRN) between the instrument cluster and the generator.

Is the repair complete?

--

System OK

--

9

Replace the bulb.

Is the repair complete?

--

System OK

--

10

Perform the battery load test. Refer to Charging System Check .

Did the battery meet the test requirements?

--

System OK

Go to Step 12

11

Replace the generator.

Is the repair complete?

--

System OK

--

12

Replace the battery.

Is the repair complete?

--

System OK

--

Battery Is Undercharged or Overcharged LG5

Battery is Undercharged or Overcharged (Cat® Diesel Engine)

Step

Action

Value(s)

Yes

No

1

  1. Disconnect the generator connector.
  2. Place the ignition switch in the RUN position.
  3. Connect a J 39200 DMM from CKT 25 (BRN) at the generator connector to the chassis ground.
  4. Observe the voltage reading on the J 39200 .

Is voltage present?

--

Go to Step 2

Go to Step 4

2

Connect a DMM J 39200 from battery terminal CKT 1 (RED) at the generator connector to the chassis ground.

Observe the voltage reading on the J 39200 .

Is voltage present?

--

Go to Step 3

Go to Step 5

3

  1. Reconnect the generator connector.
  2. Turn the accessories off.
  3. Run the engine at a fast idle.
  4. Connect a DMM J 39200 from battery terminal CKT 1 (RED) at the generator to the chassis ground.
  5. Observe the voltage reading on the J 39200 .

Does the voltage measure within the specified range?

13-16 V

Go to Step 6

Go to Step 7

4

Inspect the condition of the indicator bulb.

Is the indicator bulb in proper condition?

--

Go to Step 8

Go to Step 9

5

Locate and repair the open in CKT 1 (RED) between the generator and the starter solenoid.

Is the repair complete?

--

System OK

--

6

Perform the battery load test. Refer to Charging System Check .

Is the testing complete?

--

System OK

--

7

Perform the generator test. Refer to Charging System Check .

Does the generator meet the test requirements?

--

Go to Step 10

Go to Step 11

8

Locate and repair the open in CKT 25 (BRN) between the instrument cluster and the generator.

Is the repair complete?

--

System OK

--

9

Replace the bulb.

Is the repair complete?

--

System OK

--

10

Perform the battery load test. Refer to Charging System Check .

Did the battery meet the test requirements?

--

System OK

Go to Step 12

11

Replace the generator.

Is the repair complete?

--

System OK

--

12

Replace the battery.

Is the repair complete?

--

System OK

--