Jeep Grand Cherokee User Manual page 100

ONBOARD DIAGNOSTIC SYSTEM
(OBD)
Your vehicle is equipped with a sophisticated
onboard diagnostic system called OBD. This sys-
tem monitors the performance of the emissions,
engine, and automatic transmission control sys-
tems. When these systems are operating properly,
your vehicle will provide excellent performance
and fuel economy, as well as engine emissions
well within current government regulations.
If any of these systems require service, the OBD
system will turn on the "Malfunction Indicator
Light." It will also store diagnostic codes and other
information to assist your service technician in
making repairs. Although your vehicle will usually
be driveable and not need towing, see your
authorized dealer for service as soon as possible.
CAUTION!
Prolonged driving with the light on could cause
further damage to the emission control system.
It could also affect fuel economy and driveability.
If the light is flashing, severe catalytic converter
damage and power loss will soon occur. Immedi-
ate service is required.
98
REPLACEMENT PARTS
Use of genuine Mopar parts for normal/
scheduled maintenance and repairs is highly rec-
ommended to insure the designed performance.
Damage or failures caused by the use of non-
Mopar parts for maintenance and repairs will not
be covered by the manufacturer's warranty.
MAINTENANCE PROCEDURES
Engine Oil
Checking Oil Level — Gasoline Engines
To assure proper engine lubrication, the engine oil
must be maintained at the correct level. Check the
oil level at regular intervals, such as every fuel
stop.
The best time to check the engine oil level is about
5 minutes after a fully warmed engine is shut off or
before starting the engine after it has sat over-
night.
Checking the oil while the vehicle is on level
ground will improve the accuracy of the oil level
readings. Maintain the oil level between the MIN
and MAX or ADD and SAFE markings on the
dipstick. Adding 0.95L (1 U.S. Quart) of oil when
the reading is at the MIN mark will result in a MAX
reading on these engines.
Checking Engine Oil — Diesel Engines
Check the oil level at every fuel fill, with the engine
on level ground. If the engine is warm, allow time
for the oil to drain into the crankcase before
checking the level. The level should be between
the ADD and FULL marks on the dipstick.
Oil gets thicker at low temperatures, which will
slow down engine cranking speeds when starting.
Diesel engines require faster cranking speeds, so
be certain to use the proper oil viscosity.
CAUTION!
• When the oil level is at the ADD mark, adding
0.95L (1 U.S. Quart) will bring the level to
FULL.
• A diesel engine may consume more oil than a
gasoline engine when new. If engine oil falls
below the ADD mark, immediately add oil, or
engine damage may occur.
• DO NOT OVERFILL. Engine damage may
occur.
Change Engine Oil
Road conditions as well as your kind of driving
affect the interval at which your oil should be
changed.