Hummer H3. Manual — part 1249

3

1. Install a scan tool.

2. Turn ON the ignition, with the engine

OFF.

3. With a scan tool, command the horn

relay ON and OFF.

Do the horns turn ON and OFF with each
command?

Go to Step 11

Go to Step 4

4

1. Disconnect the horn relay.

2. 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 15

5

1. Connect a test lamp between the

battery positive voltage circuit of the
horn relay coil and the horn relay
control circuit.

2. Depress and hold the horn switch.

Does the test lamp illuminate?

Go to Step 6

Go to Step 12

6

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 7

Go to Step 16

7

Momentarily connect a 15-amp fused
jumper wire between the battery positive
voltage circuit of the horn relay switch and
the horn fuse supply voltage circuit.
Do the horns operate?

Go to Step 10

Go to Step 8

8

1. Reconnect the horn relay.

2. Disconnect the horn connector.

3. Connect a test lamp between the horn

fuse supply voltage circuit and a good
ground.

4. Depress and hold the horn switch.

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Horns - H3

Does the test lamp illuminate?

Go to Step 9

Go to Step 17

9

1. Connect a test lamp between the horn

fuse supply voltage circuit and the
horn ground circuit.

2. Depress and hold the horn switch.

Does the test lamp illuminate?

Go to Step 13

Go to Step 18

10

Inspect for poor connections at the horn
relay. Refer to Testing for Intermittent
Conditions and Poor Connections and
Connector Repairs .
Did you find and correct the condition?

Go to Step 22

Go to Step 19

11

Test the horn switch signal for a short to
voltage or open. Refer to Circuit Testing
and Wiring Repairs .
Did you find and correct the condition?

Go to Step 22

Go to Step 21

12

Test the control circuit of the horn relay
for a short to voltage or an open. Refer to
Circuit Testing and Wiring Repairs .
Did you find and correct the condition?

Go to Step 22

Go to Step 21

13

1. Connect a 15-amp fused jumper wire

between the positive battery terminal
and the horn fuse supply voltage
circuit terminal of the horn.

2. Momentarily connect another jumper

wire between the negative battery
terminal and the ground terminal of
the horn.

Does the horn sound?

Go to Step 14

Go to Step 20

14

Repair the open or high resistance in the
horn fuse supply voltage circuit or the horn
ground. A resistance as low as 0.5 ohms
could cause operating problems with the
horns. Refer to Circuit Testing and
Wiring Repairs .
Did you complete the repair?

Go to Step 22

-

Repair the open or high resistance in the

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Horns - H3

HORNS - POOR TONE

Horns - Poor Tone

15

battery positive voltage circuit of the horn
relay coil. Refer to Circuit Testing and
Wiring Repairs .
Did you complete the repair?

Go to Step 22

-

16

Repair the open or high resistance in the
battery positive voltage circuit of the horn
relay switch. Refer to Circuit Testing and
Wiring Repairs .
Did you complete the repair?

Go to Step 22

-

17

Repair the open, high resistance or short to
ground in the horn fuse supply voltage
circuit. Refer to Circuit Testing and
Wiring Repairs .
Did you complete the repair?

Go to Step 22

-

18

Repair the open or high resistance in the
horn ground circuit. Refer to Circuit
Testing and Wiring Repairs .
Did you complete the repair?

Go to Step 22

-

19

Replace the horn relay. Refer to Relay
Replacement (Attached to Wire
Harness) or Relay Replacement (Within
an Electrical Center) .
Did you complete the replacement?

Go to Step 22

-

20

Replace the horn assembly. Refer to Horn
Replacement.
Did you complete the replacement?

Go to Step 22

-

21

Replace the body control module (BCM).
Refer to Control Module References for
replacement, setup and programming.
Did you complete the replacement?

Go to Step 22

-

22

Operate the horns.
Do the horns operate properly?

System OK

Go to Step 1

Step

Action

Yes

No

Did you perform the Diagnostic System

Go to

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Horns - H3

1

Check - Vehicle?

Go to Step 2

Diagnostic
System Check -
Vehicle

2

Depress the horn switch.
Do the horns have a harsh tone or buzzing?

Go to Step 3

Go to Testing
for Intermittent
Conditions and
Poor
Connections

3

1. Test the horn mounting hardware for

adequate torque. Refer to Fastener
Tightening Specifications.

2. Inspect the horns for debris in the joint

where the horns attach to the vehicle.

Did you find and correct the condition?

Go to Step 7

Go to Step 4

4

Perform the following for each of the horns:

1. Disconnect the horn connector.

2. Connect a 15-amp fuse jumper wire

between the positive battery terminal
and the horn fuse supply voltage circuit
terminal of the horn.

3. Connect another jumper wire between

the negative battery terminal and the
ground terminal of the horn.

Does the horn have a harsh tone or buzzing?

Go to Step 6

Go to Step 5

5

Repair the high resistance in the horn fuse
supply voltage circuit or the horn ground
circuit. Refer to Circuit Testing and Wiring
Repairs .
Did you complete the repair?

Go to Step 7

-

6

Replace the horn. Refer to Horn
Replacement.
Did you complete the replacement?

Go to Step 7

-

7

Operate the horns.
Do the horns operate properly?

System OK

Go to Step 1

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Horns - H3