GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Yukon - 2WD 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Twilight Sentinel Inoperative

Step

Action

Value(s)

Yes

No

1

Did you perform the Twilight Sentinel System Check?

--

Go to Step 2

Go to Twilight Sentinel System Check

2
  1. Ensure park brake is released and park brake indicator is OFF.
  2. Place headlamps in ON position.
  3. Switch headlamp dimmer between HIGH and LOW beams.

Does the headlamp system function properly?

--

Go to Step 3

Go to Step 11

3
  1. Turn headlamps OFF.
  2. Disconnect connector C1 at headlamp control module.
  3. Turn ignition to ON.
  4. Connect a J 35616-200 test lamp between connector C1 cavity A and ground

Does test lamp light?

--

Go to Step 4

Go to Step 12

4

Connect a J 35616-200 test lamp between connector C1 cavity E and ground.

Does test lamp light?

--

Go to Step 5

Go to Step 13

5

Connect a J 35616-200 test lamp between connector C1 cavity F and B+.

Does test lamp light?

--

Go to Step 6

Go to Step 14

6

Connect a J 35616-200 test lamp between connector  C1 cavity  C and B+.

Does test lamp light?

--

Go to Step 15

Go to Step 7

7
  1. Disconnect connector C2 at headlamp control module.
  2. Connect a J 35616-200 test lamp between connector C2 cavity C and ground.

Does test lamp light?

--

Go to Step 8

Go to Step 16

8
  1. Connect both connectors C1 and C2 at headlamp control module.
  2. Turn ignition ON.
  3. Cover ambient light sensor with a dark cloth or tape.
  4. Backprobe with a J 39200 DMM between connector C2 cavity E at headlamp control module and ground

Is there continuity?

--

Go to Step 9

Go to Step 16

9

Replace headlamp control module.

Is the repair complete?

--

Go to Twilight Sentinel System Check

--

10
  1. Refer to Low and High Beams Headlamps Inoperative .
  2. Make necessary repairs.

Is the repair complete?

--

Go to Twilight Sentinel System Check

Go to Step 3

11

Locate and repair open in CKT 39 (PNK) between headlamp control module and IP fuse block.

Is the repair complete?

--

Go to Twilight Sentinel System Check

Go to Step 4

12

Locate and repair open in CKT 240 (ORN) between headlamp control module and IP fuse block.

Is the repair complete?

--

Go to Twilight Sentinel System Check

Go to Step 5

13

Locate and repair open in CKT 150 (BLK) between headlamp control module and ground G202.

Is the repair complete?

--

Go to Twilight Sentinel System Check

Go to Step 6

14
  1. Locate and repair short to ground in CKT 1134 (LT BLU) between headlamp control module and park brake warning switch.
  2. Repair faulty park brake warning indicator lamp.

Is the repair complete?

--

Go to Twilight Sentinel System Check

Go to Step 7

15

Locate and repair open in CKT 2040 (ORN) between headlamp control module and IP fuse block.

Is the repair complete?

--

Go to Twilight Sentinel System Check

Go to Step 8

16
  1. Disconnect connector C2 at headlamp control module.
  2. Disconnect connector C2 at automatic day-night mirror.
  3. Connect a J 39200 DMM between automatic day-night mirror connector C2 cavity 2 and headlamp control module connector C2 cavity E.

Is there continuity?

--

Go to Step 17

Go to Step 18

17

Replace inside automatic day-night mirror.

Is the repair complete?

--

Go to Twilight Sentinel System Check

--

18

Locate and repair open in CKT 1784 (YEL/BLK) between automatic day-night mirror and headlamp control module.

Is the repair complete?

--

Go to Twilight Sentinel System Check

Go to Step 8