GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the Charging System Check ?

--

Go to Step 2

Go to Charging System Check

2

Check the battery hydrometer.

Is the green dot visible in the hydrometer?

--

Go to Step 7

Go to Step 3

3

Diagnose the battery hydrometer. Refer to Battery Hydrometer Displays Dark or Yellow Dot .

Is the charging system diagnosis complete?

--

Go to Step 22

--

4

Perform the battery load test. Refer to Battery Not Operating Properly .

Did the battery pass the load test?

--

Go to Step 6

Go to Step 5

5

Replace the battery. Refer to Battery Replacement.

Is the repair complete?

--

Go to Step 22

--

6

Check the generator. Refer to Generator Not Operating Properly .

Does the generator operate properly?

--

Go to Step 7

Go to Step 21

7

  1. Disconnect the generator connector.
  2. Turn the ignition switch to RUN.
  3. Using a J 39200 digital multimeter (DMM) set to DC volts, measure the voltage from the generator connector terminal B (Buick) or Terminal L (Oldsmobile) to ground.

Is the measured voltage within the specified range?

5-14V

Go to Step 8

Go to Step 18

8

Check CKT 225 (RED) and CKT 23 (GRY) for an intermittent short to ground or open condition.

Are the circuits OK?

--

Go to Step 22

Go to Step 9

9

Repair CKT 225 (RED) or CKT 23 (GRY).

Is the repair complete?

--

Go to Step 22

--

10

  1. Reconnect the generator connector.
  2. Turn all the accessories off.
  3. Run the engine at a fast idle.
  4. Measure the voltage across the battery terminals.

Is the measured voltage within the specified range?

13-16V

Go to Step 22

Go to Step 11

11

Is the vehicle a Buick?

--

Go to Step 18

Go to Step 12

12

  1. Keep the engine running at fast idle.
  2. Disconnect the battery thermistor connector, located near the battery.
  3. Using a DMM set to DC volts scale, measure the voltage across the battery terminals.

Is the measured voltage in the specified range?

13-16V

Go to Step 13

Go to Step 18

13

  1. Turn the ignition switch to OFF.
  2. Using a DMM set to DC volts scale, measure the voltage at battery thermistor connector terminal A (body harness side).

Is the measured voltage in the specified range?

10-15V

Go to Step 15

Go to Step 14

14

  1. Check the BATT THERM fuse for an open.
  2. If the fuse is open, repair CKT 540 (ORN) short to ground.
  3. If the fuse is OK, repair open or high resistance in CKT 540 (ORN).

Is the repair complete?

--

Go to Step 22

--

15

  1. Disconnect the generator connector.
  2. Connect a fused jumper from generator harness connector terminal S to ground.
  3. Connect a DMM set to ohms scale between the battery thermistor connector terminal B (body harness side) and ground.

Is the measured resistance in the specified range?

Less than 5ohms

Go to Step 17

Go to Step 16

16

Repair high resistance or open in CKT 725 (LT BLU).

Is the repair complete?

--

Go to Step 22

--

17

  1. Check the battery thermistor connector for poor terminal contact.
  2. If OK, replace the battery thermistor.

Is the repair complete?

--

Go to Step 22

--

18

Check for an open or short to ground in CKT 225 (RED).

Is the circuit OK?

--

Go to Step 20

Go to Step 19

19

Repair CKT 225 (RED).

Is the repair complete?

--

Go to Step 22

--

20

  1. Check the powertrain control module (PCM) connectors for poor terminal contact.
  2. If OK, replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls.

Is the repair complete?

--

Go to Step 22

--

21

Replace the generator. Refer to Generator Replacement .

Is the repair complete?

--

Go to Step 22

--

22

Repeat the Charging System Check. Refer to Charging System Check .

Is the system check complete?

--

System OK

--