GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Corvette 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Rear Fog Lamps Inoperative

Rear Fog Lamps Inoperative

Step

Action

Value(s)

Yes

No

1

Were you sent from Foglamp System Check.

--

Go to Step 2

Go to Foglamp System Check

2

Perform the BCM Diagnostic System Check?

Are any DTCs stored in memory related to foglamp operation?

--

Go to applicable diagnostic table

Go to Step 3

3
  1. Disconnect the LH rear fog lamp connector.
  2. Connect a DMM between the LH rear fog lamp connector terminal A and ground.
  3. Turn the ignition switch to the ON position.
  4. Turn the headlamps ON.
  5. Depress the rear foglamp switch button.
  6. Measure the voltage at the LH fog lamp connector terminal A.

Is the voltage within the specified value?

10.0-14.0V

Go to Step 28

Go to Step 4

4

Does the rear fog lamp indicator illuminate?

--

Go to Step 27

Go to Step 5

5
  1. Remove the RR Fog LP Micro Relay #37.
  2. Connect a DMM between ground and the BAT terminal (switch side) in the underhood electrical center (which is used for the RR Fog LP Micro Relay #37).
  3. Measure the voltage at the underhood electrical center BAT terminal (switch side) which is used for the RR Fog LP Micro Relay #37.

Is the voltage within the specified value?

10.0-14.0V

Go to Step 6

Refer to Power Distribution

6

Check the RR FOG LP Minifuse® #1 for being open.

Is the RR FOG LP Minifuse® #1 open?

--

Go to Step 7

Go to Step 8

7

Repair the short to ground in CKT 122 between the underhood electrical center connector C2 terminal A4 and the fog lamp switch connector terminal 4 or the underhood electrical center connector C3 terminal F1 and the LH/RH fog lamp.

Is the repair complete?

--

Go to Foglamp System Check

--

8

Install a jumper wire between the BAT terminal and the CKT 122 terminal which is used for the RR FOG LP Micro Relay #37 in the underhood electrical center.

Do the rear fog lamps and the rear fog lamp indicator illuminate?

--

Go to Step 9

Go to Step 12

9
  1. Connect the DMM between ground and the BAT terminal (coil side) in the underhood electrical center which is used for the RR FOG LP Micro Relay #37.
  2. Measure the voltage at the underhood electrical center BAT terminal (coil side) which is used for the RR FOG LP Micro Relay #37.

Is the voltage within the specified values?

10.0-14.0V

Go to Step 10

Refer to Power Distribution

10
  1. Disconnect the BCM connector C1.
  2. Connect a DMM between the CKT 1901 terminal in the underhood electrical center (which is used for the RR FOG LP Micro Relay #37) and the BCM connector C1 terminal B3.
  3. Measure CKT 1901 for continuity between the underhood electrical center CKT 1901 terminal and the BCM connector C1 terminal B3.

Is CKT 1901 continuous between these two terminals?

--

Go to Step 13

Go to Step 11

11

Repair the open in CKT 1901.

Is the repair complete?

--

Go to Foglamp System Check

--

12

Repair the open in CKT 122 between:

    • the underhood electrical center connector C2 terminal E4 and the fog lamp switch connector terminal 4
    • the underhood electrical center connector C3 terminal F1 and the rear fog lamps.

Is the repair complete?

--

Go to Foglamp System Check

--

13
  1. Reinstall the RR FOG LP Micro Relay #37 into the underhood electrical center.
  2. Install a fused jumper (10 A) between the BCM connector C1 terminal B3 and ground.

Do the rear fog lamps and the rear fog lamp indicator illuminate?

--

Go to Step 15

Go to Step 14

14

Replace RR FOG LP Micro Relay #37.

Is the repair complete?

--

Go to Foglamp System Check

--

15
  1. Disconnect the rear fog lamp switch connector.
  2. Connect a DMM between the rear fog lamp switch connector terminal 1 and ground.
  3. Measure the voltage at the rear fog lamp switch connector terminal 1.

Is the voltage within the specified value?

10.0-14.0V

Go to Step 22

Go to Step 16

16

Check the F/TNK DR Minifuse® #32 for an open.

Is the fuse open?

--

Go to Step 18

Go to Step 17

17
  1. Remove the F/TNK DR Minifuse® #32.
  2. Connect a DMM between the instrument panel electrical center terminal A (which is used for the F/TNK DR Minifuse® #32) and ground.
  3. Measure the voltage at instrument panel electrical center terminal A.

Is the voltage within the specified values?

10.0-14.0V

Go to Step 19

Refer to Power Distribution

18
  1. Remove the F/TNK DR Minifuse® #32.
  2. Leave the rear fog lamp switch still disconnected.
  3. Connect a DMM between the instrument panel electrical center terminal B (which is used for the F/TNK DR Minifuse® #32) and ground.
  4. Measure CKT 2840 for continuity to ground.

Is CKT 2840 shorted to ground?

--

Go to Step 20

Go to Step 21

19

Repair the open in CKT 2840.

Is the repair complete?

--

Go to Foglamp System Check

--

20

Repair the short to ground in CKT 2840.

Is the repair complete?

--

Go to Foglamp System Check

--

21

Repair the short to ground in CKT 187.

Is the repair complete?

--

Go to Foglamp System Check

--

22
  1. Disconnect the BCM Connector C2.
  2. Connect a DMM between the BCM connector C2 terminal D5 and the rear fog lamp switch connector terminal 6.
  3. Measure CKT 187 for continuity between the BCM connector C2 terminal D5 and the rear fog lamp switch connector terminal 6.

Is CKT 187 continuous between these two connectors?

--

Go to Step 23

Go to Step 24

23
  1. Reconnect the rear fog lamp switch connector.
  2. Connect a DMM between the BCM connector C2 terminal D5 and ground.
  3. Press the rear fog lamp switch button.
  4. Measure the voltage at the BCM connector C2 terminal D5 with the rear fog lamp switch button depressed.

Is the voltage within the specified values?

10.0-14.0V

Go to Step 25

Go to Step 26

24

Repair the open in CKT 187.

Is the repair complete?

--

Go to Foglamp System Check

--

25

Replace the BCM.

Is the repair complete?

--

Go to Foglamp System Check

--

26

Replace the rear fog lamp switch.

Is the repair complete?

--

Go to Foglamp System Check

--

27
  1. Disconnect the LH/RH rear foglamp connectors.
  2. Connect a DMM between the LH/RH rear foglamp connector terminal A and the underhood electrical center connector C3 terminal F1.
  3. Measure CKT 122 for continuity between the underhood electrical center connector C3 terminals F1 and the LH/RH rear foglamp connectors.

Is CKT 122 continuous between these two connectors?

--

Go to Step 32

Go to Step 31

28
  1. Disconnect the LH/RH rear foglamp connectors.
  2. Connect a DMM between the LH/RH rear foglamp connector terminal A and ground.
  3. Measure CKT 150 for continuity between the LH/RH rear foglamp connector terminal G and ground.

Is CKT 150 continuous to ground?

--

Go to Step 30

Go to Step 29

29

Repair the open in CKT 150 between the foglamp connector and G401.

Is the repair complete?

--

Go to Foglamp System Check

--

30

Replace the inoperative foglamp bulb.

Is the repair complete?

--

Go to Foglamp System Check

--

31

Repair the open in CKT 122.

Is the repair complete?

--

Go to Foglamp System Check

--

32

Replace the underhood electrical center.

Is the repair complete?

--

Go to Foglamp System Check

--