GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2000 🢒 DeVille 🢒 Body and Accessories 🢒 Horns 🢒 Horns Inoperative

Step

Action

Yes

No

SCHEMATIC REFERENCE: Horn Schematics

1

Did you perform the Horn Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Horns

2

Depress the horn switch.

Do the horns operate normally?

Go to Step 3

Go to Step 4

3
  1. Turn ON the ignition, with the engine OFF.
  2. Install a scan tool.
  3. With a scan tool, command the horn relay ON and OFF.

Do the horns operate normally?

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

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Remove the horn relay.
  3. Connect a test lamp between the battery positive voltage circuit of the horn relay coil and a good ground.

Does the test lamp illuminate?

Go to Step 5

Go to Step 18

5
  1. Turn OFF the ignition.
  2. Connect a test lamp between the horn relay control circuit and the battery positive voltage circuit of the horn relay coil.
  3. Turn ON the ignition, with the engine OFF.
  4. Depress and hold the horn switch.

Does the test lamp illuminate?

Go to Step 6

Go to Step 12

6

With a scan tool, command the horn relay ON and OFF.

Does the test lamp illuminate?

Go to Step 7

Go to Step 13

7

Connect a test lamp between the battery positive voltage circuit of the horn relay switch and a good ground.

Does the test lamp illuminate?

Go to Step 8

Go to Step 19

8

Connect a 15 amp fused jumper wire between the battery positive voltage circuit of the horn relay switch and the supply voltage circuit of the horns.

Do the horns sound?

Go to Step 14

Go to Step 9

9
  1. Disconnect the horns.
  2. Connect a test lamp between the supply voltage circuit of the horns and the ground circuit of the horns.

Does the test lamp illuminate?

Go to Step 11

Go to Step 10

10

Connect a test lamp between the supply voltage circuit of the horns and a good ground.

Does the test lamp illuminate?

Go to Step 21

Go to Step 20

11
  1. Connect a 15 amp fused jumper wire between the positive terminals of the horns and battery positive voltage.
  2. Connect another jumper wire between the ground terminals of the horns and a good ground.

Do the horns sound?

Go to Step 16

Go to Step 25

12

Caution: This vehicle is equipped with a Supplemental Inflatable Restraint (SIR) System. Failure to follow the correct procedure could cause the following conditions:

   • Air bag deployment
   • Personal injury
   • Unnecessary SIR system repairs
In order to avoid the above conditions, observe the following guidelines:
   • Refer to SIR Component Views in order to determine if you are performing service on or near the SIR components or the SIR wiring.
   • If you are performing service on or near the SIR components or the SIR wiring, disable the SIR system. Refer to Disabling the SIR System.

Important: The horn switch circuit includes the inflatable restraint steering wheel module coil.

  1. Disable the SIR system. Refer to Disabling the SIR System in SIR.
  2. Test the horn switch portion of the horn relay control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 15

13

Test the horn relay control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

Go to Step 17

14

Inspect for a poor connection at the harness connectors of the horn relay. 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 27

Go to Step 23

15

Inspect for a poor connection at the harness connectors of the horn 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 27

Go to Step 24

16

Inspect for a poor connection at the harness connectors of the horns. 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 27

Go to Step 22

17

Inspect for poor connections at the harness connector of the Dash Integration Module. 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 27

Go to Step 26

18

Repair an open or high resistance in the battery positive voltage circuit of the horn relay coil. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

--

19

Repair an open or high resistance in the battery positive voltage circuit of the horn relay switch. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

--

20

Repair an open or high resistance in the supply voltage circuits of the horns. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

--

21

Repair an open or high resistance in the ground circuits of the horns. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

--

22

Repair the high resistance in the supply voltage and ground circuits of the horns. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 27

--

23

Replace the horn relay. Refer to Horn Relay Replacement .

Did you complete the replacement?

Go to Step 27

--

24

Caution: This vehicle is equipped with a Supplemental Inflatable Restraint (SIR) System. Failure to follow the correct procedure could cause the following conditions:

   • Air bag deployment
   • Personal injury
   • Unnecessary SIR system repairs
In order to avoid the above conditions, observe the following guidelines:
   • Refer to SIR Component Views in order to determine if you are performing service on or near the SIR components or the SIR wiring.
   • If you are performing service on or near the SIR components or the SIR wiring, disable the SIR system. Refer to Disabling the SIR System.

Important: The horn switch is part of the steering wheel module inflatable restraint and is not serviceable separately.

Replace the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement in SIR.

Did you complete the replacement?

Go to Step 27

--

25

Replace the dual horn assembly. Refer to Horn Replacement .

Did you complete the replacement?

Go to Step 27

--

26

Replace the Dash Integration Module (DIM). Refer to Dash Integration Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 27

--

27

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Step 2