Jeep 1997 Grand Cherokee Service Manual page 457

ZG
DIAGNOSIS AND TESTING (Continued)
(5) The coil ground terminal (85) is connected to
the electromagnet in the relay. It is grounded
through the horn switch when the horn switch is
depressed. It can also be grounded by the Body Con-
trol Module (BCM) in response to inputs from the
Vehicle Theft Security System (VTSS) or the Remote
Keyless Entry (RKE) system. Check for continuity to
ground at the cavity for relay terminal 85. There
should be continuity with the horn switch depressed,
and no continuity with the horn switch released. If
not OK, see the diagnosis for the Horn Switch in this
group.
HORN SWITCH
For circuit descriptions and diagrams, refer to
8W-41 - Horns/Cigar Lighter in Group 8W - Wiring
Diagrams.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING WHEEL,
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable. Remove the lower steering column cover/knee
blocker. Check for continuity between the metal
steering column jacket and a good ground. There
should be continuity. If OK, go to Step 2. If not OK,
refer to Group 19 - Steering and check for proper
installation of the steering column ground clip.
(2) Remove the driver side airbag module as
described in Group 8M - Passive Restraint Systems.
Unplug the horn switch wire harness connectors
from the airbag module. Unplug the Body Control
Module (BCM) wire harness connector B (white).
Unplug the horn relay from the Power Distribution
Center (PDC). 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 3. If not OK,
repair the short circuit as required.
(3) Check for continuity between the steering col-
umn half of the horn switch feed wire harness con-
nector and the horn relay control circuit cavity for
the horn relay in the PDC. There should be continu-
ity. If OK, go to Step 4. If not OK, repair the open
circuit as required.
(4) Check for continuity between the horn switch
feed wire and the horn switch ground wire on the
airbag module. There should be no continuity. If OK,
go to Step 5. If not OK, replace the faulty horn
switch.
GROUP 8M - PASSIVE
STEERING COLUMN,
POWER DISTRIBUTION CEN-
NEGATIVE CABLE
(5) Depress the center of the airbag module cover
and check for continuity between the horn switch
feed wire and the horn switch ground wire on the
airbag module. There should now be continuity. If not
OK, replace the faulty horn switch.
HORN
For circuit descriptions and diagrams, refer to
8W-41 - Horns/Cigar Lighter in Group 8W - Wiring
Diagrams.
(1) Unplug the horn wire harness connector. Mea-
sure the resistance between the ground circuit cavity
of the horn wire harness connector and a good
ground. There should be no measurable resistance. If
OK, go to Step 2. If not OK, repair the circuit to
ground as required.
(2) With the horn wire harness connector still
unplugged, depress the horn switch. There should be
battery voltage at the horn relay output circuit cavity
of the horn wire harness connector. If OK, replace
the faulty horn. If not OK, repair the open circuit to
OR
the horn relay as required.
REMOVAL AND INSTALLATION
HORN RELAY
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the cover from the Power Distribution
Center (PDC) (Fig. 1).
Fig. 1 Power Distribution Center
(3) Refer to the label on the PDC for horn relay
identification and location.
(4) Unplug the horn relay from the PDC.
(5) Install the horn relay by aligning the relay ter-
minals with the cavities in the PDC and pushing the
relay firmly into place.
(6) Install the PDC cover.
(7) Connect the battery negative cable.
TER
HORN SYSTEMS 8G - 3