GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the Lighting Systems Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Verify that the low beam headlamps are inoperative.

Do the headlamps operate normally?

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Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

Inspect the PARK LP 20 A fuse in the Underhood Fuse Block.

Is the fuse open?

--

Go to Step 4

Go to Step 7

4

  1. Remove the Headlamp Grounding Relay and the Headlamp Power Relay.
  2. Test the B+ circuit to the Multifunction Switch (Headlamp Switch), the Headlamp Switch Headlamps On Signal circuit, and the Headlamp Relay Coil Supply Voltage circuit for a short to ground. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

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Go to Step 5

Go to Step 6

5

Locate and repair the short to ground in the B+ circuit to the Multifunction Switch (Headlamp Switch), the Headlamp Switch Headlamps On Signal circuit, or the Headlamp Relay Coil Supply Voltage circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

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Go to Step 22

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6

Test the Headlamp Grounding Relay and the Headlamp Power Relay for an internal short to the ground terminal and replace as necessary. Refer to Circuit Testing in Wiring Systems.

Is the repair complete?

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Go to Step 22

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7

  1. Move the Multifunction Switch (Headlamp Switch) to the ON (HEAD) position.
  2. Place the Multifunction Switch (Headlamp Switch) in the LOW BEAMS position.
  3. Remove the Headlamp Power Relay.
  4. Connect a test lamp between the Headlamp Relay Coil Supply Voltage circuit terminal and the Ground circuit terminal of the relay socket. Refer to Circuit Testing in Wiring Systems.

Does the test lamp Illuminate?

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Go to Step 11

Go to Step 8

8

Test the following circuits for an open or high resistance. Refer to Circuit Testing in Wiring Systems.

    • B+ to the Multifunction Switch (Headlamp Switch).
    •  Headlamp Switch Headlamps On Signal.
    • Headlamp Relay Coil Supply Voltage.
    • Headlamp Power Relay ground.

Was a problem found?

--

Go to Step 9

Go to Step 10

9

Locate and repair the open or high resistance in the following circuits. Refer to Wiring Repairs in Wiring Systems.

    • B+ to the Multifunction Switch (Headlamp Switch).
    •  Headlamp Switch Headlamps On Signal.
    • Headlamp Relay Coil Supply Voltage.
    • Headlamp Power Relay ground.

Is the repair complete?

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Go to Step 22

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10

Replace the Multifunction Switch (Headlamp Switch). Refer to Turn Signal Switch Replacement - On Vehicle in Steering Wheel and Column - Tilt.

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Go to Step 22

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11

Connect the test lamp from ground to the Headlamp Low beam Supply Voltage circuit terminal of either inoperative headlamp socket. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

--

Go to Step 13

Go to Step 12

12

Replace the Headlamp Power Relay.

Is the repair complete?

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Go to Step 22

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13

Connect the test lamp between the Headlamp Low Beam Supply Voltage circuit terminal and CKT 525 (YEL) terminal of either inoperative headlamp socket. Refer to Circuit Testing in Wiring Systems.

Does the test lamp illuminate?

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Go to Step 14

Go to Step 15

14

Replace both Low Beam Headlamps.

Is the repair complete?

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Go to Step 22

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15

  1. Remove the Flash To Pass Relay.
  2. Connect a test lamp from ground to the Headlamp Switch Flash to Pass Signal circuit at the relay socket. Refer to Circuit Testing in Wiring Systems.

Does the test lamp light?

--

Go to Step 16

Go to Step 19

16

Test the Headlamp Switch Flash to Pass Signal circuit for a short to B+. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

--

Go to Step 17

Go to Step 18

17

Locate and repair the short to B+ in the Headlamp Switch Flash to Pass Signal circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 22

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18

Replace the Multifunction Switch (Headlamp Switch). Refer to Turn Signal Switch Replacement - On Vehicle in Steering Wheel and Column - Tilt.

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Go to Step 22

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19

Test for an open or high resistance in CKT 525 (YEL) and the Flash To Pass Relay ground circuit. Refer to Circuit Testing in Wiring Systems.

Was a problem found?

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Go to Step 20

Go to Step 21

20

Locate and repair the open or high resistance in CKT 525 (YEL) or the Flash To Pass Relay ground circuit. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 22

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21

Replace the flash to pass relay.

Is the repair complete?

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Go to Step 22

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22

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 3