GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the Horn Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Horns

2

Inspect the HORN fuse at the underhood fuse block.

Is the fuse functional?

--

Go to Step 4

Go to Step 3

3

Locate and repair the overload and replace the HORN fuse.

Refer to Circuit Testing in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

4

  1. Disconnect the right horn connector.
  2. Connect a test lamp between the right horn CKT 29 (DK GRN) cavity B to ground.
  3. Press the horn button.

Does the test lamp illuminate?

--

Go to Step 5

Go to Step 6

5

Connect a DMM between the right horn connector CKT 350 (BLK) cavity A to ground.

Did you find continuity?

--

Go to Step 7

Go to Step 8

6

  1. Disconnect the left horn connector.
  2. Connect a test lamp between the left horn CKT 29 (DK GRN) cavity B to ground.
  3. Press the horn button.

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 10

7

Replace the right horn. Refer to Horn Replacement .

Did you complete the replacement?

--

Go to Step 25

--

8

Repair the open in CKT 350 (BLK).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

9

Connect a DMM between the left horn connector CKT 250 (BLK) cavity A to ground.

Did you find continuity?

--

Go to Step 11

Go to Step 12

10

  1. Reconnect both of the horn connectors.
  2. Disconnect the horn relay from the convenience center.
  3. Connect a test lamp between CKT 740 (ORN) cavity H4 at the horn relay to ground.

Does the test lamp illuminate?

--

Go to Step 14

Go to Step 13

11

Replace the left horn. Refer to Horn Replacement .

Did you complete the replacement?

--

Go to Step 25

--

12

Repair the open in CKT 250 (BLK).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

13

Repair the open in CKT 740 (ORN).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

14

Momentarily connect a fused jumper between the horn relay cavity H4 to cavity G6.

Did the horns sound?

--

Go to Step 15

Go to Step 16

15

Connect a test lamp between the horn relay CKT 740 (ORN) cavity G4 to ground.

Does the test lamp illuminate?

--

Go to Step 17

Go to Step 18

16

Repair the open in CKT 29 (DK GRN).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

17

  1. Connect a test lamp between the horn relay cavity H6 to cavity G4.
  2. Press the horn button.

Does the test lamp illuminate?

--

Go to Step 19

Go to Step 20

18

Repair the open in CKT 740 (ORN).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

19

Replace the horn relay.

Did you complete the repair?

--

Go to Step 25

--

20

  1. Reconnect the horn relay.
  2. Disconnect the horn switch connector.
  3. Momentarily connect a fused jumper from the horn switch connector to ground.

Did the horns sound?

--

Go to Step 21

Go to Step 22

21

Replace the horn switch.

Refer to Horn Switch Replacement - On Vehicle in Steering Wheel and Column - Standard.

Did you complete the replacement?

--

Go to Step 25

--

22

Inspect for an open in the wiring between the horn switch and the convenience center.

Refer to Circuit Testing in Wiring Systems.

Did you find an open?

--

Go to Step 23

Go to Step 24

23

Repair the open in CKT 28 (BLK).

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 25

--

24

Replace the horn brush and the horn slip ring. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column - Standard. Turn Signal and Multifunction Switch Assembly - Disassemble - Off Vehicle Turn Signal and Multifunction Switch Assembly - Assemble - Off Vehicle in Steering Wheel and Column - Tilt.

Did you complete the repair?

--

Go to Step 25

--

25

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2