Hummer H3. Manual — part 1248

SCAN TOOL DATA LIST

The Horns Scan Tool Data List contains all of the horn related parameters that are available on
the scan tool. The parameters in the list are arranged in alphabetical order. The column, "Data
List," indicates the location of the parameter within the scan tool menu selections. Use the Horns
Scan Tool Data List as directed by a diagnostic table or in order to supplement the diagnostic
procedures. Begin all of the diagnostic procedures with Diagnostic System Check - Vehicle .

Use the Scan Tool Data List only after the following is determined:

There is no published DTC procedure nor published symptom procedure for the customer
concern.

The DTC or symptom diagnostic procedure indicated by the diagnostic system check does
not resolve the customer concern.

The Typical Data Values are obtained from a properly operating vehicle under the conditions
specified in the first row of the Scan Tool Data List table. Comparison of the parameter values
from the suspect vehicle with the Typical Data Value(s) may reveal the source of the customer
concern.

Scan Tool Data List

SCAN TOOL DATA DEFINITIONS

Battery Voltage

The scan tool displays the current state of the battery in volts.

Horn Relay Command

Horn Relay

Theft Deterrent,
Special Functions,
Body Control
Module

The body control module (BCM) activates the horn
relay momentarily when you select On.

Scan Tool Parameter

Data List

Units Displayed

Typical Data

Value

Operating Conditions: Ignition ON/Engine OFF

Battery Voltage

Data

Volts

Varies

Horn Relay Command

Outputs

On/Off

Off

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Horns - H3

The scan tool displays On/Off to indicate the current state of the horn relay as commanded
by the body control module (BCM) or the horn switch.

SYMPTOMS - HORNS

Review the system operation in order to familiarize yourself with the system functions. Refer to
Horns System Description and Operation.

Visual/Physical Inspection

Inspect for aftermarket devices which could affect the operation of the horn system. Refer to
Checking Aftermarket Accessories .

Inspect the easily accessible or visible system components for obvious damage or conditions
which could cause the symptom.

Perform the following if a horn buzzes or has a harsh tone:

Inspect for debris in the joint where the horn fastens to the vehicle.

Test the torque of the horn mounting hardware. The horn mounting hardware should be
tightened to a torque of 10 N.m (7 lb ft).

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to
Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the
symptom:

Horns Always On

Horns Inoperative

Horns - Poor Tone

HORNS ALWAYS ON

Test Description

The number below refers to the step number on the diagnostic table.

IMPORTANT: The following steps must be completed before using the symptom

tables:

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Horns - H3

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

Horns Always On

Step

Action

Yes

No

1

Did you perform the Diagnostic System
Check - Vehicle?

Go to Step 2

Go to
Diagnostic
System Check -
Vehicle

2

Depress and release the horn switch.
Are the horns ON at all times?

Go to Step 3

Go to Testing
for Intermittent
Conditions and
Poor
Connections

3

Disconnect the body control module
(BCM).
Are the horns ON at all times?

Go to Step 4

Go to Step 8

4

Disconnect the horn relay.
Are the horns ON at all times?

Go to Step 10

Go to Step 5

5

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 7

Go to Step 6

6

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 13

Go to Step 12

7

Repair the short to ground in the horn relay
control circuit. Refer to Circuit Testing
and Wiring Repairs .
Did you complete the repair?

Go to Step 13

-

8

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

Go to Step 13

Go to Step 9

9

Inspect for poor connections at the harness
connector of the BCM. Refer to Testing
for Intermittent Conditions and Poor

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Horns - H3

HORNS INOPERATIVE

Test Description

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

4: Tests for voltage at the battery positive voltage terminal of the horn relay coil.

6: Tests for voltage at the battery positive voltage terminal of the horn relay switch. The
HORN fuse supplies power to the battery positive voltage terminal of the horn relay switch.

14: The horns need maximum current flow to operate properly. A high resistance (greater
than 0.5 ohms) in the horn control circuit or the horn ground circuit could cause operating
problems with the horns. Inspect the circuits for faults that would restrict current flow.

Horns Inoperative

Connections and Connector Repairs .
Did you find and correct the condition?

Go to Step 13

Go to Step 11

10

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

Go to Step 13

-

11

Replace the BCM. Refer to Control
Module References for replacement, setup
and programming.
Did you complete the replacement?

Go to Step 13

-

12

Replace the horn relay.
Did you complete the replacement?

Go to Step 13

-

13

Operate the horns.
Do the horns operate properly?

System OK

Go to Step 1

Step

Action

Yes

No

1

Did you perform the Diagnostic System
Check - Vehicle?

Go to Step 2

Go to
Diagnostic
System Check -
Vehicle

2

Depress the horn switch.
Do the horns operate?

Go to Testing
for Intermittent
Conditions and
Poor
Connections

Go to Step 3

2007 Hummer H3

2007 ACCESSORIES & EQUIPMENT Horns - H3