GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

  1. Turn the ignition switch to the OFF position.
  2. Turn OFF all the electrical accessory loads.
  3. Turn load off in the J 41450-B.
  4. Connect the J 41450-B to the vehicle battery terminals.
  5. Install inductive ammeter around output wire (CKT 2 - Red) of generator.
  6. Perform J 41450-B self test in order to verify proper operation.
  7. Connect red clip of tester to generator output terminal (CKT 2).
  8. Connect the black clip to metal surface on generator housing.
  9. Observe the green POWER lamp the J 41450-B.

Does the green POWER lamp illuminate?

--

Go to Step 2

Go to Step 6

2

  1. Disconnect the generator 4-way electrical connector.
  2. Connect the matching connector on the J 41450-B to the generator.
  3. Observe the red DIAGNOSTIC lamp on J 41450-B.

Does the red DIAGNOSTIC lamp illuminate?

--

Go to Step 3

Go to Step 8

3

  1. Start the engine.
  2. Allow engine to idle for 1 minute.
  3. Observe the red DIAGNOSTIC lamp on the J 41450-B.

Does the red DIAGNOSTIC lamp turn off?

--

Go to Step 4

Go to Step 9

4

  1. Increase engine speed to 2500 rpm.
  2. Observe the red DIAGNOSTIC lamp on J 41450-B.

Does the red DIAGNOSTIC lamp remain off?

--

Go to Step 5

Go to Step 9

5

  1. Maintain engine speed at 2500 rpm.
  2. Set the load on the J 41450-B to 77 amperes.
  3. Observe the red DIAGNOSTIC lamp on J 41450-B.

Does the red DIAGNOSTIC lamp remain off?

--

Go to Step 15

Go to Step 9

6

Using J 39200 , measure the voltage between the generator output terminal (circuit 2) and the negative battery terminal.

Is the voltage measured within the specified range?

B+ (10-14 V)

Go to Step 7

Go to Step 10

7

  1. Leave the DMM connected from the previous step.
  2. Connect a jumper wire between the negative battery terminal and the metal housing of the generator.
  3. Observe the green POWER lamp on J 41450-B.

Does the green POWER lamp illuminate?

--

Go to Step 11

Go to Step 12

8

  1. Turn the ignition switch to the OFF position.
  2. Disconnect J 41450-B 4-way connector from generator.
  3. Disconnect the PCM connector C2.
  4. Using a DMM, measure the voltage between the generator harness connector terminal L and ground.

Is the voltage measured within the specified value?

Less than 2 V

Go to Step 9

Go to Step 13

9

  1. Replace the generator. Refer to Generator Replacement or Generator Replacement or Generator Replacement .
  2. Recheck the system.

Is the repair complete?

--

Go to Step 14

--

10

  1. Repair a poor connection or an open in CKT 2.
  2. Recheck the system.

Is the repair complete?

--

Go to Step 14

--

11

  1. Repair a poor connection or an open between the generator and ground.
  2. Recheck the system.

Is the repair complete?

--

Go to Step 14

--

12

  1. Inspect for a faulty J 41450-B. Refer to the manufacturer's instructions for more information.
  2. Recheck the system.

Is the repair complete?

--

Go to Step 1

--

13

  1. Repair a short to B+ in CKT 225.
  2. Recheck the system.

Is the repair complete?

--

Go to Step 14

--

14

  1. Turn off the load on J 41450-B.
  2. Disconnect J 41450-B from the vehicle.
  3. Reconnect the generator connector.
  4. Recheck the system.

Is the repair complete?

--

Go to Charging System Check

--

15

  1. Turn off load on J 41450-B.
  2. Stop the engine.
  3. Disconnect J 41450-B from the vehicle.
  4. Reconnect the generator connector.
  5. If the battery shows erratic or high voltage, inspect the generator connector terminal D (CKT 2740) for an open or intermittent poor connection.
  6. If the battery is losing charge over a period of time, inspect for excessive parasitic loads. Refer to Battery Electrical Drain/Parasitic Load
  7. Recheck the system.

Is the repair complete?

--

Go to Charging System Check

--