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DN HORN SYSTEMS 8G - 1
HORN SYSTEMS
TABLE OF CONTENTS
page page
DESCRIPTION AND OPERATION
HORN SYSTEM...........................1
HORN ..................................1
HORN RELAY ............................2
HORN SWITCH...........................2
DIAGNOSIS AND TESTING
HORN SWITCH...........................3
DESCRIPTION AND OPERATION
HORN SYSTEM
DESCRIPTION
A dual-note electric horn system is standard factory-installed equipment on this model. The standard
equipment horn system features one low-note horn
unit and one high-note horn unit. The horn system
uses a non-switched source of battery current so that
the system will remain functional, regardless of the
ignition switch position. The horn system includes
the following components:
• Clockspring
• High-line Central Timer Module (CTM)
• Horns
• Horn relay
• Horn switch
Refer to Clockspring in the Description and Operation section of Group 8M - Passive Restraint Systems for more information on this component. Refer
to Central Timer Module in the Description and
Operation section of Group 8E - Instrument Panel
Systems for more information on this component.
Refer to Horn/Cigar Lighter/Power Outlet in the
Contents of Group 8W - Wiring Diagrams for complete circuit diagrams. Following are general descriptions of the remaining major components in the horn
system.
OPERATION
The horn system is activated by a horn switch concealed beneath the driver side airbag module trim
cover in the center of the steering wheel. Depressing
the center of the driver side airbag module trim cover
closes the horn switch. Closing the horn switch activates the horn relay. The activated horn relay then
switches the battery current needed to energize the
horns.
HORN ..................................3
REMOVAL AND INSTALLATION
HORN RELAY ............................4
HORN ..................................4
Refer to the owner’s manual in the vehicle glove
box for more information on the features, use and
operation of the horn system.
CENTRAL TIMER MODULE
The high-line Central Timer Module (CTM) can
also operate the horn system. A high-line CTM is
used on high-line versions of this vehicle. The CTM
combines the functions of a chime/buzzer module, an
intermittent wipe module, an illuminated entry module, a remote keyless entry module, and a vehicle
theft security system module in a single unit.
The high-line CTM also controls and integrates
many of the additional electronic functions and features included on models with this option. The horn
relay is one of the hard wired outputs of the CTM.
The high-line CTM is programmed to energize or deenergize the horn relay in response to certain inputs
from the Remote Keyless Entry (RKE) system and/or
the Vehicle Theft Security System (VTSS).
Refer to Central Timer Module in the Description and Operation section of Group 8E - Instrument
Panel Systems for more information on the high-line
CTM. Refer to Remote Keyless Entry System in
the Description and Operation section of Group 8P Power Lock Systems for more information on the
RKE system. Refer to Vehicle Theft Security Sys-
tem in the Description and Operation section of
Group 8Q - Vehicle Theft/Security Systems for more
information on the VTSS.
HORN
DESCRIPTION
The dual electromagnetic diaphragm-type horns
are standard equipment on this model. Both horns
are mounted on a single bracket that is secured to
the front of the left vertical member of the radiator
support, just behind the radiator grille and forward
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8G - 2 HORN SYSTEMS DN
DESCRIPTION AND OPERATION (Continued)
of the radiator. The high-note horn is connected in
parallel with the low-note horn. The horns are connected to the vehicle electrical system through the
headlamp and dash wire harness. Each horn is
grounded through its wire harness connector and a
ground circuit to an eyelet terminal secured by a
ground screw located on the right front inner fender
behind the right headlamp, and receives battery current through the closed contacts of the horn relay.
Both horns and the mounting bracket are serviced
as a single unit. The horns cannot be repaired or
adjusted and, if faulty or damaged, the entire horn
and bracket unit must be replaced.
OPERATION
Within the two halves of the molded plastic horn
housing are a flexible diaphragm, a plunger, an electromagnetic coil and a set of contact points. The diaphragm is secured in suspension around its
perimeter by the mating surfaces of the horn housing. The plunger is secured to the center of the diaphragm and extends into the center of the
electromagnetic coil. The contact points control the
current flow through the electromagnet.
When the horn is energized, electrical current
flows through the closed contact points to the electromagnet. The resulting electromagnetic field draws
the plunger and diaphragm toward it until that
movement mechanically opens the contact points.
When the contact points open, the electromagnetic
field collapses allowing the plunger and diaphragm to
return to their relaxed positions and closing the contact points again. This cycle continues repeating at a
very rapid rate producing the vibration and movement of air that creates the sound that is directed
through the horn outlet.
HORN RELAY
DESCRIPTION
The horn relay is a electromechanical device that
switches battery current to the horn when the horn
switch grounds the relay coil. The horn relay is
located in the Junction Block (JB), on the left end of
the instrument panel in the passenger compartment.
If a problem is encountered with a continuously
sounding horn, it can usually be quickly resolved by
removing the horn relay from the JB until further
diagnosis is completed. See the fuse and relay layout
label affixed to the inside surface of the fuse access
panel for horn relay identification and location.
The horn relay is a International Standards Organization (ISO) micro-relay. Relays conforming to the
ISO specifications have common physical dimensions,
current capacities, terminal patterns, and terminal
functions. The ISO micro-relay terminal functions
are the same as a conventional ISO relay. However,
the ISO micro-relay terminal pattern (or footprint) is
different, the current capacity is lower, and the physical dimensions are smaller than those of the conventional ISO relay.
The horn relay cannot be repaired or adjusted and,
if faulty or damaged, it must be replaced.
OPERATION
The ISO relay consists of an electromagnetic coil, a
resistor or diode, and three (two fixed and one movable) electrical contacts. The movable (common feed)
relay contact is held against one of the fixed contacts
(normally closed) by spring pressure. When the electromagnetic coil is energized, it draws the movable
contact away from the normally closed fixed contact,
and holds it against the other (normally open) fixed
contact.
When the electromagnetic coil is de-energized,
spring pressure returns the movable contact to the
normally closed position. The resistor or diode is connected in parallel with the electromagnetic coil in the
relay, and helps to dissipate voltage spikes that are
produced when the coil is de-energized.
HORN SWITCH
DESCRIPTION
A center-blow, normally open, resistive membranetype horn switch is secured with heat stakes to the
back side of the driver side airbag module trim cover
in the center of the steering wheel (Fig. 1). The
switch consists of two plastic membranes, one that is
flat and one that is slightly convex. These two membranes are secured to each other around the perimeter. Inside the switch, the centers of the facing
surfaces of these membranes each has a grid made
with an electrically conductive material applied to it.
One of the grids is connected to a circuit that provides it with continuity to ground at all times. The
grid of the other membrane is connected to the horn
relay control circuit.
The steering wheel and steering column must be
properly grounded in order for the horn switch to
function properly. The horn switch is only serviced as
a part of the driver side airbag module trim cover. If
the horn switch is damaged or faulty, or if the driver
side airbag is deployed, the driver side airbag module
trim cover and horn switch must be replaced as a
unit.
OPERATION
When the center area of the driver side airbag trim
cover is depressed, the electrically conductive grids
on the facing surfaces of the horn switch membranes
contact each other, closing the switch circuit. The
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DN HORN SYSTEMS 8G - 3
DESCRIPTION AND OPERATION (Continued)
Steering Column in the Removal and Installation
section of Group 19 - Steering for proper installation
of the steering column.
(3) Remove the driver side airbag module from the
steering wheel. Disconnect the horn switch wire harness connectors from the driver side airbag module.
(4) Remove the horn relay from the Junction Block
(JB). Check for continuity between the steering column half of the horn switch feed wire harness connector and a good ground. There should be no
continuity. If OK, go to Step 5. If not OK, repair the
shorted horn relay control circuit to the horn relay in
the JB as required.
(5) Check for continuity between the steering column half of the horn switch feed wire harness connector and the horn relay control circuit cavity for
the horn relay in the JB. There should be continuity.
If OK, go to Step 6. If not OK, repair the open horn
Fig. 1 Driver Side Airbag Module Trim Cover and
Horn Switch
1 – RETAINER SLOTS
2 – RETAINER SLOTS
3 – HORN SWITCH
4 – LOCKING BLOCKS
completed horn switch circuit provides a ground for
the control coil side of the horn relay, which activates
the relay. When the horn switch is released, the
resistive tension of the convex membrane separates
the two electrically conductive grids and opens the
switch circuit.
DIAGNOSIS AND TESTING
HORN SWITCH
For complete circuit diagrams, refer to Horn/Ci-
gar Lighter/Power Outlet in the Contents of
Group 8W - Wiring Diagrams.
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, REFER TO GROUP 8M - PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING WHEEL, STEERING COLUMN, OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable. Remove the steering column opening cover
from the instrument panel.
(2) Check for continuity between the metal steering column jacket and a good ground. There should
be continuity. If OK, go to Step 3. If not OK, refer to
relay control circuit to the horn relay in the JB as
required.
(6) Check for continuity between the horn switch
feed wire and the horn switch ground wire on the
driver side airbag module. There should be no continuity. If OK, go to Step 7. If not OK, replace the
faulty horn switch.
(7) Depress the center of the driver side airbag
module trim cover and check for continuity between
the horn switch feed wire and the horn switch
ground wire on the driver side airbag module. There
should now be continuity. If not OK, replace the
faulty horn switch.
HORN
For complete circuit diagrams, refer to Horn/Cigar Lighter/Power Outlet in the Contents of
Group 8W - Wiring Diagrams.
(1) Disconnect the wire harness connector(s) from
the horn connector receptacle(s). Measure the resistance between the ground circuit cavity of the horn(s)
wire harness connector(s) and a good ground. There
should be no measurable resistance. If OK, go to Step
2. If not OK, repair the open ground circuit to ground
as required.
(2) Check for battery voltage at the horn relay output circuit cavity of the horn(s) wire harness connector(s). There should be zero volts. If OK, go to Step 3.
If not OK, repair the shorted horn relay output circuit or replace the faulty horn relay as required.
(3) Depress the horn switch. There should now be
battery voltage at the horn relay output circuit cavity
of the horn(s) wire harness connector(s). If OK,
replace the faulty horn(s). If not OK, repair the open
horn relay output circuit to the horn relay as
required.
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8G - 4 HORN SYSTEMS DN
REMOVAL AND INSTALLATION
HORN RELAY
WARNING: ON VEHICLES EQUIPPED WITH AIRBAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISOLATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYSTEM CAPACITOR TO DISCHARGE BEFORE PERFORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRECAUTIONS COULD RESULT IN ACCIDENTAL AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the fuse access panel by inserting a
finger in the finger recess molded into the panel and
then pulling the panel sharply away from the left
outboard end of the instrument panel (Fig. 2).
INSTALLATION
(1) See the fuse and relay layout label affixed to
the inside of the fuse access panel for the proper
horn relay location.
(2) Position the horn relay in the proper receptacle
in the JB.
(3) Align the horn relay terminals with the terminal cavities in the JB receptacle.
(4) Push in firmly on the horn relay until the terminals are fully seated in the terminal cavities in the
JB receptacle.
(5) Insert the tabs on the forward edge of the fuse
access panel in the notches on the forward edge of
the instrument panel fuse access panel opening.
(6) Press the rear edge of the fuse access panel in
toward the instrument panel until the panel snaps
back into place.
(7) Reconnect the battery negative cable.
HORN
REMOVAL
(1) Disconnect and isolate the battery negative
cable.
(2) Disconnect the headlamp and dash wire harness connectors from the horn connector receptacles
(Fig. 3).
Fig. 2 Horn Relay Remove/Install
1 – INSTRUMENT PANEL
2 – JUNCTION BLOCK
3 – FUSE ACCESS PANEL
4 – HORN RELAY
(3) See the fuse and relay layout label affixed to
the inside of the fuse access panel for horn relay
identification and location.
(4) Grasp the horn relay firmly and pull it straight
out from the JB.
Fig. 3 Horns Remove/Install
1 – RADIATOR SUPPORT
2 – HEADLAMP AND DASH WIRE HARNESS
3 – LOW NOTE
4 – SCREW
5 – HORN AND BRACKET
6 – HIGH NOTE
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DN HORN SYSTEMS 8G - 5
REMOVAL AND INSTALLATION (Continued)
(3) Remove the screw that secures the horn and
mounting bracket unit to the front of the left vertical
member of the radiator support.
(4) Remove the horn and mounting bracket unit
from the radiator support.
INSTALLATION
(1) Position the horn and mounting bracket unit
onto the front of the left vertical member of the radiator support.
(2) Install and tighten the screw that secures the
horn and mounting bracket unit to the radiator support. Tighten the screw to 10.7 N·m (95 in. lbs.).
(3) Reconnect the headlamp and dash wire harness
connectors to the horn connector receptacles.
(4) Reconnect the battery negative cable.
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