GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 4WD 🢒 Body and Accessories 🢒 Horns 🢒 Horns Always On

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests if ground is constantly being applied to the horn relay.

    2.

  2. The horn relay control circuit includes the horn switch. The horn switch is part of the inflatable restraint steering wheel module. The horn switch must be tested for a short to ground when testing the relay control circuit.

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check-Horns?

Go to Step 2

Go to Diagnostic System Check - Horns

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the body control module (BCM) Horn Output ON and OFF.

Are the horns on at all times?

Go to Step 3

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

3
  1. Turn OFF the ignition.
  2. Disconnect the horn relay.

Are the horns on at all times?

Go to Step 8

Go to Step 4

4

Connect a test lamp between the battery positive voltage circuit of the horn relay coil and the horn relay control circuit.

Does the test lamp illuminate?

Go to Step 5

Go to Step 6

5

Important: The horn switch is part of the inflatable restraint steering wheel module. Refer to Inflatable Restraint Steering Wheel Module Replacement in SIR.

To disable the SIR system refer to Disabling the SIR System in SIR.

Test the horn relay control circuit for a short to ground. The horn relay control circuit includes the horn switch. Refer to Circuit Testing , and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 7

6

Inspect for poor connections at the horn relay. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 11

Go to Step 9

7

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

Did you find and correct the condition?

Go to Step 11

Go to Step 10

8

Repair the short to voltage in the horn control circuit. Refer to Circuit Testing , and to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 11

--

9

Replace the horn relay. Refer to Horn Relay Replacement in Horns.

Did you complete the replacement?

Go to Step 11

--

10

Important: Perform the BCM setup procedure when replacing the BCM.

Replace the BCM. Refer to Body Control Module Replacement in Body Control Systems.

Did you complete the replacement?

Go to Step 11

--

11

Operate the horns.

Do the horns operate properly?

System OK

Go to Step 1