Power-Up Mode; Diagnosis And Testing; Relays; Vehicle Theft Security System - Jeep 1997 Grand Cherokee Service Manual

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DESCRIPTION AND OPERATION (Continued)

POWER-UP MODE

When the vehicle immobilizer system senses that
the vehicle battery has been disconnected and recon-
nected, it enters its power-up mode. If the immobi-
lizer system was armed prior to the battery
disconnect, the system remains armed when the bat-
tery is reconnected.
If the immobilizer system was disarmed prior to
the battery disconnect, the system will remain dis-
armed if the battery is reconnected within five min-
utes. The system will passively arm itself when the
battery is reconnected more than five minutes after a
battery disconnect or failure. After any passive arm-
ing, the system will have to be actively disarmed
using one of the transmitters.
The power-up mode logic also applies if the battery
goes dead, and battery jump-starting is attempted.
The engine no-run feature will prevent the engine
from operating until the vehicle immobilizer system
has been actively disarmed.

DIAGNOSIS AND TESTING

VEHICLE THEFT SECURITY SYSTEM

The vehicle theft security system should be diag-
nosed using the DRB scan tool and the proper Body
Diagnostic Procedures Manual. Refer to 8W-39 -
Vehicle Theft Security System in Group 8W - Wiring
Diagrams for complete circuit descriptions and dia-
grams.
Self-Diagnostics
The vehicle theft security system has a self-diag-
nostic mode that can be entered using the DRB scan
tool. Refer to the proper Body Diagnostic Procedures
Manual for more information on this feature.

RELAYS

The horn relay is located in the Power Distribution
Center (PDC) in the engine compartment. The auto
headlamp and park lamp relays are located in the
junction block in the passenger compartment. Each
of these relays can be tested as described in the fol-
lowing procedure, however the circuits they are used
in do vary. To test the relay circuits, refer to the cir-
cuit descriptions and diagrams in 8W-39 - Vehicle
Theft Security System in Group 8W - Wiring Dia-
grams.
VEHICLE THEFT/SECURITY SYSTEMS
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.
Remove the relay from the PDC or junction block
as described in this group to perform the following
tests:
(1) A relay in the de-energized position should
have continuity between terminals 87A and 30, and
no continuity between terminals 87 and 30. If OK, go
to Step 2. If not OK, replace the faulty relay.
(2) Resistance between terminals 85 and 86 (elec-
tromagnet) should be 75
3. If not OK, replace the faulty relay.
(3) Connect a battery to terminals 85 and 86.
There should now be continuity between terminals
30 and 87, and no continuity between terminals 87A
and 30. If OK, test the relay circuits. If not OK,
replace the faulty relay.
Relay Terminals
GROUP 8M - PASSIVE
STEERING COLUMN,
5 ohms. If OK, go to Step
8Q - 5
OR