GM Service Manual Online
For 1990-2009 cars only

Headlamps Inoperative - One Lamp Domestic

Step

Action

Value(s)

Yes

No

1

Was the Headlamp Diagnostic System Check performed?

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Go to Step 2

Go to Headlight System Check

2

  1. Disconnect the inoperative headlamp connector.
  2. Turn the headlamp switch to the HEAD position.
  3. Complete the following steps if the low beam is inoperative:
  4. • Turn the headlamp dimmer switch to the LOW position.
    • Use a test lamp in order to backprobe from the inoperative headlamp connector terminal B to ground.
  5. Complete the following steps if the high beam is inoperative:
  6. • Turn the headlamp dimmer switch to the HIGH position.
    • Use a test lamp in order to backprobe from the inoperative headlamp connector terminal C to ground.

Did the test lamp light?

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Go to Step 3

Go to Step 4

3

    • If the low beam is inoperative, use a test lamp in order to frontprobe the inoperative headlamp connector B to headlamp connector A.
    • If the high beam is inoperative, use a test lamp in order to frontprobe the inoperative headlamp connector C to headlamp connector A.

Did the test lamp light?

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Go to Step 6

Go to Step 7

4

  1. Complete the following steps for the left headlamp:
  2. • For the low beam, use a test lamp in order to backprobe between the underhood accessory junction block harness C3 terminal B8 and ground.
    • For the high beam, use a test lamp in order to backprobe between the underhood accessory junction block harness C3 terminal B4 and ground.
  3. Complete the following steps for the right headlamp:
  4. • For the low beam, use a test lamp in order to backprobe between the underhood accessory junction block harness C3 terminal A8 and ground.
    • For the high beam, use a test lamp in order to backprobe between the underhood accessory junction block harness C3 terminal A4 and ground.

Did the test lamp light?

--

Go to Step 5

Go to Step 8

5

    • For the low beam, repair an open in CKT 12 between the underhood accessory junction block harness connector and the inoperative headlamp connector terminal B.
    • For the high beam, repair an open in CKT 11 between the underhood accessory junction block harness connector and the inoperative headlamp connector terminal C.

Has the repair been completed?

--

Go to Headlight System Check

--

6

Replace the headlamp. Refer to Headlamp Replacement .

Has the repair been completed?

--

Go to Headlight System Check

--

7

    • For the left headlamp, repair an open in CKT 1350 between the headlamp connector terminal A and G101.
    • For the right headlamp, repair an open in CKT 1250 between the headlamp connector terminal A and G102.

Has the repair been completed?

--

Go to Headlight System Check

--

8

    • For the low beam, use a test lamp in order to backprobe between the underhood accessory junction block harness connector C2 terminal F8 to ground.
    • For the high beam, use a test lamp in order to backprobe between the underhood accessory junction block harness connector C2 terminal F4 to ground.

Did the test lamp light?

--

Go to Step 9

Go to Step 10

9

Replace the underhood accessory junction block. Refer to Relay/Fuse Center Replacement

Has the repair been completed?

--

Go to Headlight System Check

--

10

Voltage is not present to illuminate the low beams or the high beams.

Are the low beam headlamps inoperative or the highbeam headlamps inoperative?

--

Go to Headlamps Inoperative - Low Beams or Headlamps Inoperative - High Beams

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Headlamps Inoperative - One Lamp Export

Step

Action

Value(s)

Yes

No

1

Was the Headlamp Diagnostic System Check performed?

--

Go to Step 2

Go to Headlight System Check

2

  1. Disconnect the inoperative headlamp connector.
  2. Turn the headlamp switch to the HEAD position.
  3. Complete the following steps if the low beam is inoperative:
  4. • Turn the headlamp dimmer switch to the LOW position.
    • Use a test lamp in order to backprobe from the inoperative headlamp connector terminal B to ground.
  5. Complete the following steps if the high beam is inoperative:
  6. • Turn the headlamp dimmer switch to the HIGH position.
    • Use a test lamp in order to backprobe from the inoperative headlamp connector terminal C to ground.

Did the test lamp light?

--

Go to Step 3

Go to Step 4

3

    • If the low beam is inoperative, use a test lamp in order to frontprobe the inoperative headlamp connector B to headlamp connector A.
    • If the high beam is inoperative, use a test lamp in order to frontprobe the inoperative headlamp connector C to headlamp connector A.

Did the test lamp light?

--

Go to Step 6

Go to Step 7

4

  1. Complete the following steps for the left headlamp:
  2. • For the low beam, use a test lamp in order to backprobe between the underhood electrical center connector C3 terminal A8 and ground.
    • For the high beam, use a test lamp in order to backprobe between the underhood electrical center connector C3 terminal A4 and ground.
  3. Complete the following steps for the right headlamp:
  4. • For the low beam, use a test lamp in order to backprobe between the underhood electrical center connector C3 terminal A12 and ground.
    • For the high beam, use a test lamp in order to backprobe between the underhood electrical center connector C3 terminal E11 and ground.

Did the test lamp light?

--

Go to Step 5

Go to Step 8

5

    • For the low beam, repair an open in CKT 12 between the underhood electrical center connector and the inoperative headlamp connector terminal B.
    • For the high beam, repair an open in CKT 11 between the underhood electrical center connector and the inoperative headlamp connector terminal C.

Has the repair been made and the system rechecked?

--

Go to Headlight System Check

--

6

Replace the headlamp. Refer to Headlamp Replacement .

Has the repair been made and the system rechecked?

--

Go to Headlight System Check

--

7

    • For the left headlamp, repair an open in CKT 1350 between the headlamp connector terminal A and G101.
    • For the right headlamp, repair an open in CKT 1250 between the headlamp connector terminal A and G102.

Has the repair been made and the system rechecked?

--

Go to Headlight System Check

--

8

  1. Complete the following steps for the left headlamp:
  2. • For the low beam, use a test lamp in order to backprobe between the underhood electrical center connector C2 terminal F8 and ground.
    • For the high beam, use a test lamp in order to backprobe between the underhood electrical center connector C2 terminal F4 and ground.
  3. Complete the following steps for the right headlamp:
  4. • For the low beam, use a test lamp in order to backprobe between the underhood electrical center connector C2 terminal F12 and ground.
    • For the high beam, use a test lamp in order to backprobe between the underhood electrical center connector C2 terminal E11 and ground.

Did the test lamp light?

--

Go to Step 9

Go to Step 10

9

Replace the underhood electrical center. Refer to Relay/Fuse Center Replacement

Has the repair been made and the system rechecked?

--

Go to Headlight System Check

--

10

    • For the left low beam, repair an open in CKT 712 between the underhood electrical center connector C2 terminal F8 and the fuse block terminal C4.
    • For the left high beam, repair an open in CKT 711 between the underhood electrical center connector C2 terminal F4 and the fuse block terminal B4.
    • For the right low beam, repair an open in CKT 312 between the underhood electrical center connector C2 terminal F12 and the fuse block terminal C2.
    • For the right high beam, repair an open in CKT 311 between the underhood electrical center connector C2 terminal E11 and the fuse block terminal B2.

Has the repair been made and the system rechecked?

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Go to Headlamps Inoperative - Low Beams or Headlamps Inoperative - High Beams

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