GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2000 🢒 Yukon Denali 🢒 Body and Accessories 🢒 Horns 🢒 Horns Inoperative

Step

Action

Value(s)

Yes

No

1

Did you perform the Horns System Check?

--

Go to Step 2

Go to Horns System Check

2
  1. Disconnect the horn(s).
  2. Connect a DMM between cavity A of the horn connector and ground.

Is there continuity?

--

Go to Step 4

Go to Step 3

3

Locate and repair the open in CKT 250 (BLK) between the horn connector and G112. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Horns System Check

--

4
  1. Connect a DMM between cavity B of the horn connector and ground.
  2. Depress the horn switch.

Is there battery voltage?

--

Go to Step 5

Go to Step 6

5

Replace the defective horn.

Refer to Horn Replacement .

Is the repair complete?

--

Go to Horns System Check

--

6
  1. Remove the horn relay from the underhood fuse block.
  2. Connect a DMM from cavity C3 of the underhood fuse block to ground.

Is there battery voltage?

--

Go to Step 8

Go to Step 7

7

Locate and repair the open in CKT 740 (ORN) between the underhood fuse block and the HORN fuse. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Horns System Check

--

8

Connect a DMM between the underhood fuse block cavity D3 and ground.

Is there battery voltage?

--

Go to Step 9

Go to Step 7

9

Connect a DMM between cavity C3 and cavity D1 of the horn relay.

Is there continuity?

--

Go to Step 12

Go to Step 10

10
  1. Connect a DMM between cavity C1 of the underhood fuse block and ground.
  2. Depress the horn switch.

Is there continuity?

--

Go to Step 11

Go to Step 13

11

Locate and repair the open in CKT 28 (BLK) between the underhood fuse block and the horn connector(s). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Horns System Check

--

12

Replace the horn relay.

Is the repair complete?

--

Go to Horns System Check

--

13
  1. Disconnect C266.
  2. Connect a DMM between the underhood fuse block cavity C1 and C266 cavity A11.

Is there continuity?

--

Go to Step 15

Go to Step 14

14

Locate and repair the open in CKT 28 (BLK) between the underhood fuse block and C266. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Horns System Check

--

15
  1. Disconnect the horn switch.
  2. Connect a DMM between C266 cavity A11 and horn switch feed side.

Is there continuity?

--

Go to Step 16

Go to Step 17

16

Replace the horn switch.

Refer to Horn Switch Replacement - On Vehicle in Manual Steering.

Is the repair complete?

--

Go to Horns System Check

--

17

Locate and repair the open in CKT 28 (BLK) between C266 and the horn switch. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Horns System Check

--