Important Preliminary Checks Before Starting: Perform A Diagnostic System Check - Horns before using the symptom tables
in order to verify that all of the following are true:
| • | The body control module (BCM) can communicate via the serial data
link. |
Visual/Physical Inspection
Several of the symptom procedures ask for a careful visual/physical
check. This step is extremely important-it could lead to correcting a problem
without further checks and can save valuable time. These checks include
the following:
| • | Inspect for aftermarket devices which could affect the operation
of the Horn System. Refer to Checking Aftermarket Accessories in Wiring Systems. |
| • | Inspect the easily accessible or visible system components and
harness connectors for obvious damage or conditions which could cause the
symptom. |
| • | Perform the following If the 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). |
Intermittents
Important: Check for proper installation of electrical components if an intermittant
condition exists. Inspect for aftermarket theft deterrent devices, lights
and cellular phones. Ensure that no aftermarket equipment is connected
to the class 2 circuit. If you can not locate an intermittent condition,
a cellular phone signal may cause the condition. Faulty electrical connections
or wiring may also be the cause of intermittent conditions. Refer to
Testing for Intermittent and Poor Connections in Wiring Systems.
Important: The problem may or may not turn on the SERVICE VEHICLE SOON indicator
or store a DTC. Do not use the symptom tables to diagnose intermittent conditions.
The malfunction must be present in order to locate the problem.
Poor electrical connections or wiring cause most intermittent conditions.
Perform a careful visual/physical check for the following conditions:
| • | Poor mating of the connector halves or a terminal not fully seated
in the connector body (backed out). |
| • | An improperly formed or damaged terminal. |
| • | Reform or replace connector terminals in the problem circuit in
order to insure proper contact tension. |
| • | Poor terminal to wire connection requires removing the terminal
from the connector body in order to perform the check. |
Road test the vehicle with a J 39200 digital multimeter (DMM) connected
to the suspected circuit. An abnormal voltage when the malfunction occurs
is a good indication that there is a malfunction in the circuit being
monitored.
Use a Scan Tool in order to help detect intermittent conditions. The
scan tool has several features that can be used to locate an intermittent
condition. The snapshot feature can capture and store data parameters
within the scan tool when the malfunction occurs. This information can
then be reviewed in order to see what caused the malfunction.
Symptom List
Refer to a symptom diagnostic procedure from the following list in order
to diagnose a symptom that does not set a DTC:
