GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Safari - 4WD 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Low and High Beams Headlamps Inoperative

Step

Action

Value(s)

Yes

No

1

Did you perform the Lighting Diagnostic System Check?

--

Go to Step 2

Diagnostic System Check - Lighting Systems

2

Check the following fuses:

    • 40A LIGHTING fuse #8 in the underhood fuse block.
    • 15A RH HEADLAMP fuse.
    • 15A LH HEADLAMP fuse.

Are the fuses functional?

--

Go to Step 4

Go to Step 3

3

Locate overload and replace fuse(s).

Is the repair complete?

--

Go to Step 20

--

4

With DMM, check for battery voltage from cavity D CKT 1840 (ORN) of the headlamp switch to ground.

Is battery voltage present?

B+

Go to Step 6

Go to Step 5

5

Locate and repair OPEN in CKT 1840 (ORN) between the headlamp switch and splice S330.

Is the repair complete?

--

Go to Step 20

--

6
  1. Turn the headlamp switch to the HEAD position.
  2. With DMM, check for battery voltage from cavity C CKT 352 (WHT) of the headlamp switch to ground.

Is battery voltage present?

B+

Go to Step 8

Go to Step 7

7

Replace the headlamp switch. Headlamp Switch Replacement

Is the repair complete?

--

Go to Step 20

--

8

Probe the following two cavities of the headlamp relay with DMM for battery voltage (located in the underhood fuse block):

    • A1 - CKT 352 (WHT)
    • A3 - CKT 42 (RED)

Is battery voltage present at both cavities?

B+

Go to Step 10

Go to Step 9

9

Locate and repair the OPEN in one of the CKT's:

  1. CKT 352 (WHT) between the headlamp relay and the headlamp switch.
  2. CKT 42 (RED) between the headlamp relay and the lighting fuse (located within underhood fuse block).

Is the repair complete?

--

Go to Step 20

--

10
  1. Turn OFF the headlamp switch.
  2. Remove headlamp relay.
  3. With DMM, measure resistance of relay pins 85 and 86.

Is resistance within specified range?

40-110ohms

Go to Step 12

Go to Step 11

11

Replace the headlamp relay.

Is the repair complete?

--

Go to Step 20

--

12
  1. Reconnect headlamp relay.
  2. Place the headlamp switch in the HEAD position.
  3. With DMM, check for battery voltage from cavity B1 of the headlamp relay to ground.

Is battery voltage present?

B+

Go to Step 13

Go to Step 11

13

Using a DMM, check for continuity of ground CKT 250 (BLK) between cavity B3 of the headlamp relay to ground G101.

Is continuity present?

--

Go to Step 15

Go to Step 14

14

Locate and repair OPEN in CKT 250 (BLK) between cavity B3 of the headlamp relay to ground G101.

Is the repair complete?

--

Go to Step 20

--

15

Check for battery voltage at both headlamp fuses located in the underhood fuse block.

Is battery voltage present?

B+

Go to Step 17

Go to Step 16

16
  1. Check for OPEN in CKT 1346 (LT BLU) located in the underhood fuse block.
  2. If no OPEN, replace underhood fuse block.

Is the repair complete?

--

Go to Step 20

--

17

Check for battery voltage at cavity E13 of steering column connector C201.

Is battery voltage present?

B+

Go to Step 19

Go to Step 18

18
  1. Check for OPEN in CKT 544 (LT BLU) between C201 and the steering column multi-function switch.
  2. If no OPEN found, replace the steering column multi-function switch.

Is the repair complete?

--

Go to Step 20

--

19

Locate and repair OPEN in CKT 544 (PPL) between C201 and the DRL relay.

Is the repair complete?

--

Go to Step 20

--

20

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2