GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Montana - 4WD 🢒 Body 🢒 Lighting Systems 🢒 Courtesy Lamps Inoperative

Step

Action

Yes

No

Schematic Reference: Interior Lights Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

DEFINITION: One or all of the following courtesy lamps do not illuminate when the instrument panel (I/P) dimmer switch is in the DOME position:

    • Cargo lamp
    • Dome lamps
    • Footwell courtesy lamps
    • Courtesy reading lamps

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Turn ON the interior lamps override switch, interior lamps enabled.
  2. Turn the dimmer switch to the DOME position.

Are all of the courtesy lamps illuminated?

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

Go to Step 3

3

Are all of the courtesy lamps inoperative?

Go to Step 4

Go to Step 12

4

Enter the body control module (BCM) Input/Output Diagnostic Mode. Refer to On-Board Diagnostic Features in Body Control System.

Does the BCM perform the output test?

Go to Step 5

Go to Step 7

5
  1. Cycle the dimmer switch from the DOME position to the OFF position and back to the DOME position in order to move to output test mode 2.
  2. Manually turn ON the roof rail reading lamp switches and the vanity mirror lamps.

Do the roof rail reading lamps and the vanity mirror lamps illuminate?

Go to Step 6

Go to Step 10

6
  1. Disconnect the BCM connector.
  2. Connect a fused jumper between the courtesy lamps supply voltage circuit of the BCM connector and battery voltage. Refer to Circuit Testing in Wiring Systems.
  3. Connect a fused jumper between the courtesy lamps low control circuit of the BCM connector and ground. Refer to Circuit Testing in Wiring Systems.

Do the courtesy lamp illuminate?

Go to Step 18

Go to Step 29

7
  1. Disconnect the headlamp switch connector.
  2. Using a test lamp connected to battery positive voltage, probe the ground circuit of the headlamp switch.

Does the test lamp illuminate?

Go to Step 8

Go to Step 23

8

Connect a fused jumper between the courtesy lamps switch signal circuit and the ground circuit of the headlamp switch connector. Refer to Circuit Testing in Wiring Systems.

Do the courtesy lamps illuminate?

Go to Step 21

Go to Step 9

9

Test the courtesy lamps switch signal circuit for an open, high resistance, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 35

Go to Step 18

10
  1. Disconnect the interior lamp override switch.
  2. Probe the courtesy lamps supply voltage circuit of the interior lamp override switch with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 11

Go to Step 14

11

Connect a fused jumper between the courtesy lamps supply voltage circuit and the interior lamp defeat switch signal circuit of the interior lamp override switch connector. Refer to Circuit Testing in Wiring Systems.

Do any of the interior lamps illuminate?

Go to Step 22

Go to Step 24

12
  1. Remove the inoperative courtesy lamp bulb.
  2. Using a test lamp, probe between the courtesy lamps supply voltage circuit and the ground circuit of the inoperative interior lamp bulb.

Does the test lamp illuminate?

Go to Step 19

Go to Step 13

13
  1. Disconnect the inoperative courtesy lamp connector.
  2. Using a test lamp connected to ground, probe the courtesy lamps supply voltage circuit of the inoperative courtesy lamp connector.

Does the test lamp illuminate?

Go to Step 16

Go to Step 27

14
  1. Disconnect the BCM connector.
  2. Using a test lamp connected to ground, probe the battery positive voltage circuit of the BCM connector that is supplied by the CTSY LAMP fuse.

Does the test lamp illuminate?

Go to Step 15

Go to Step 17

15
  1. Connect a fused jumper between the battery positive voltage circuit and the courtesy lamps supply voltage circuit of the BCM connector. Refer to Circuit Testing in Wiring Systems.
  2. Probe the courtesy lamps supply voltage circuit of the interior lamp override switch with a test lamp that is connected to ground.

Does the test lamp illuminate?

Go to Step 18

Go to Step 26

16

Using a test lamp connected to battery positive voltage, probe the courtesy lamps low control circuit of the inoperative courtesy lamp.

Does the test lamp illuminate?

Go to Step 20

Go to Step 28

17

Test for an open or high resistance in the battery positive voltage circuit of the BCM that is supplied by the CTSY LAMP fuse. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 35

Go to Step 25

18

Inspect for a poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 35

Go to Step 30

19

Inspect for poor connections at the bulb socket of the inoperative courtesy lamp. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 35

Go to Step 31

20

Inspect for a poor connections at the harness connector of the inoperative courtesy lamp. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 35

Go to Step 32

21

Inspect for a poor connections at the harness connector of the headlamp switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 35

Go to Step 33

22

Inspect for a poor connections at the harness connector of the interior lamps override switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 35

Go to Step 34

23

Repair the open, high resistance, or short to battery positive voltage in the ground circuit of the headlamp switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 35

--

24

Repair the open or high resistance in the signal circuit of the interior lamp override switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 35

--

25

Repair the short to ground in the battery positive voltage circuit or the courtesy lamps supply voltage circuit of the BCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 35

--

26

Repair the open, high resistance, or short to ground in the courtesy lamp supply voltage circuit of the BCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 35

--

27

Repair the open or high resistance in the courtesy lamp supply voltage circuit of the inoperative courtesy lamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 35

--

28

Repair the open or high resistance in the courtesy lamp low control circuit of the inoperative courtesy lamp. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 35

--

29

Repair the open, high resistance, or short to battery voltage in the courtesy lamps low control circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 35

--

30

Replace the BCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the repair?

Go to Step 35

--

31

Replace the inoperative courtesy lamp bulb. Refer to the appropriate procedure.

    •  Dome Lamp Replacement
    •  Cargo Lamp Replacement

Did you complete the repair?

Go to Step 35

--

32

Replace the inoperative courtesy lamp. Refer to the appropriate procedure.

    •  Dome Lamp Replacement
    •  Cargo Lamp Replacement

Did you complete the repair?

Go to Step 35

--

33

Replace the headlamp switch. Refer to Headlamp Switch Replacement .

Did you complete the repair?

Go to Step 35

--

34

Replace the interior lamps override switch. Refer to Interior Lamp and Multifunction Switch Replacement .

Did you complete the repair?

Go to Step 35

--

35

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2