GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 4WD 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Tail, Marker, and License Lamps Inoperative

Step

Action

Value(s)

Yes

No

1

Did you perform the Exterior Lights System Check?

--

Go to Step 2

Go to Exterior Lights System Check

2

Use a scan tool in order to read the current body control module (BCM) diagnostic trouble codes (DTCs).

Are any current DTCs set?

--

Go to Diagnostic System Check - Body Control System in Body Control System

Go to Step 3

3

Inspect the PARK LP fuse in the underhood fuse block.

Is the PARK LP fuse in the underhood fuse block open?

--

Go to Step 13

Go to Step 4

4

Connect a test lamp between CKT 240 (ORN) at the headlamp switch and ground.

Does the test lamp light?

--

Go to Step 6

Go to Step 5

5

Locate and repair the open in CKT 240 (ORN).

Is the repair complete?

--

Go to Exterior Lights System Check

--

6
  1. Connect a test lamp between CKT 74 (LT BLU) at the headlamp switch and ground.
  2. Move the headlamp switch to the PARK position.

Does the test lamp light?

--

Go to Step 8

Go to Step 7

7

Replace the headlamp switch. Refer to Headlamp Switch Replacement .

Is the repair complete?

--

Go to Exterior Lights System Check

--

8
  1. Remove the PARK LP fuse from the IP Fuse Block.
  2. Connect a test lamp between the feed side of the PARK LP fuse at the IP fuse block and ground.

Does the test lamp light?

--

Go to Step 10

Go to Step 9

9

Locate and repair the open in CKT 74 (LT BLU) between the headlamp switch and the IP Fuse Block.

Is the repair complete?

--

Go to Exterior Lights System Check

--

10
  1. Remove the bolts from the underhood fuse block in order to gain access to the bottom of the underhood fuse block.
  2. Backprobe between CKT 74 (LT BLU) cavity A4 connector C1 and ground.

Does the test lamp light?

--

Go to Step 11

Go to Step 12

11

Replace the underhood fuse block.

Is the repair complete?

--

Go to Exterior Lights System Check

--

12

Locate and repair the open in CKT 74 (LT BLU) between the IP fuse block and the underhood fuse block.

Is the repair complete?

--

Go to Exterior Lights System Check

--

13
  1. Disconnect the headlamp switch.
  2. Connect a test lamp between CKT 240 (ORN) and battery power.

Does the test lamp light?

--

Go to Step 14

Go to Step 15

14
  1. Locate and repair the short to ground in CKT 240 (ORN).
  2. Replace the PARK LP fuse in the underhood fuse block.

Is the repair complete?

--

Go to Exterior Lights System Check

--

15
  1. Remove the PARK LP fuse from the IP fuse block.
  2. Disconnect connector C1 from the underhood fuse block.
  3. Connect a test lamp between CKT 74 (LT BLU) cavity A at the headlamp switch and battery power.

Does the test lamp light?

--

Go to Step 16

Go to Step 17

16

Locate and repair the short to ground in CKT 74 (LT BLU).

Is the repair complete?

--

Go to Exterior Lights System Check

--

17
  1. Reconnect the underhood fuse block connector C1.
  2. Remove the following components:
    3. • The fog lamp relay
    • The RR PRK fuse
    • The LR PRK fuse
    • The TRL PRK fuse
    • The FR PRK fuse
  3. Connect a test lamp between CKT 74 (LT BLU) cavity A at the headlamp switch and battery power.

Does the test lamp light?

--

Go to Step 18

Go to Step 19

18

Replace the underhood fuse block.

Is the repair complete?

--

Go to Exterior Lights System Check

--

19

Locate and repair the intermittent short to ground in CKT 240 (ORN) or CKT 74 (LT BLU).

Is the repair complete?

--

Go to Exterior Lights System Check

--