GM Service Manual Online
For 1990-2009 cars only

Horns Inoperative

Step

Action

Value(s)

Yes

No

1

Were you sent here from the Horns Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - Horns

2

  1. Remove the HORN MiniFuse® #11.
  2. Probe the fuse terminal B in the underhood electrical center with a test light.
  3. Depress the horn switch.

Does the test light illuminate?

--

Go to Step 10

Go to Step 3

3

  1. Remove the HORN Micro Relay #36.
  2. Connect a DMM between the circuit 28 terminal in the underhood electrical center and ground.
  3. Measure resistance to ground of circuit 28 with the horn switch depressed.
  4. Is the resistance within specified values?

0-2 ohms

Go to Step 6

Go to Step 4

4

Caution: When you are performing service on or near the SIR components or the SIR wiring, you must disable the SIR system. Refer to Disabling the SIR System. Failure to follow the correct procedure could cause air bag deployment, personal injury, or unnecessary SIR system repairs.

  1. Remove the drivers side inflator module from the steering wheel.
  2. Disconnect the horn brush slip ring connector inside the steering wheel.
  3. Connect a DMM between the horn brush slip ring terminal in the steering wheel and the circuit 28 terminal in the underhood electrical center.
  4. Measure the resistance of circuit 28.

Is the resistance within specified values?

0-2 ohms

Go to Step 5

Go to Step 7

5

  1. Disconnect the horn ground strap pigtail terminal in the steering wheel.
  2. Connect a DMM between the horn ground terminal in the steering wheel and ground.
  3. Measure the resistance of circuit 150 to ground.

Is the resistance within specified values?

0-2 ohms

Go to Step 9

Go to Step 8

6

Replace the HORN Micro Relay #36. Refer to Horn Relay Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

7

Repair the open in circuit 28.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

8

Repair the open in circuit 150.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

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9

Replace the horn switch. Refer to Horn Switch Replacement - On Vehicle .

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

10

Check the HORN MiniFuse® #11.

Is the fuse open?

--

Go to Step 13

Go to Step 11

11

  1. Disconnect the horn connector.
  2. Connect a DMM between the horn fuse terminal A in the underhood electrical center and the horn connector terminal B.
  3. Measure the resistance of circuit 29.

Is the resistance within specified values?

0-2 ohms

Go to Step 12

Go to Step 14

12

  1. Connect a DMM between the horn connector terminal A and ground.
  2. Measure the resistance to ground of circuit 150.

Is the resistance within specified values?

0-2 ohms

Go to Step 16

Go to Step 15

13

  1. Disconnect the horn connector.
  2. Connect a DMM between the horn fuse terminal A in the underhood electrical center and ground.
  3. Measure the resistance to ground of circuit 29.

Is the resistance within specified values?

Infinite

Go to Step 16

Go to Step 17

14

Repair an open in CKT 29.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

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15

Repair an open in CKT 150.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

16

Replace the horn assembly. Refer to Horn Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - Horns

--

17

Repair the short to ground in circuit 29.

Is the repair complete?

--

Go to Diagnostic System Check - Horns

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