JEEP GRAND CHEROKEE 2008 WK / 3.G Owners Manual

If temperatures are below 32ÉF (0ÉC), operate the engine
at moderate speeds for 5 minutes before full loads are
applied.
Engine Idling - In Cold Weather
Avoid prolonged idling in ambient temperatures below
0ÉF (-18ÉC). Long periods of idling may be harmful to
your engine because combustion chamber temperatures
can drop so low that the fuel may not burn completely.
Incomplete combustion allows carbon and varnish to
form on piston rings and injector nozzles. Also, the
unburned fuel can enter the crankcase, diluting the oil
and causing rapid wear to the engine.
Stopping The Engine
Before turning off your turbo diesel engine, always
allow the engine to return to normal idle speed and runfor several seconds. This assures proper lubrication of
the turbocharger. This is particularly necessary after
any period of hard driving.
Idle the engine a few minutes before routine shutdown.
After full load operation, idle the engine 3 to 5 minutes
before shutting it down. This idle period will allow the
lubricating oil and coolant to carry excess heat away from
the combustion chamber, bearings, internal components,
and turbocharger. This is especially important for turbo-
charged, charge air cooled engines.
The following chart should be used as a guide in deter-
mining the amount of engine idle time required to
sufficiently cool down the turbocharger before shut
down, depending upon the type of driving and the
amount of cargo.
STARTING AND OPERATING 281
5

TURBOCHARGER9COOL DOWN9CHART
Driving Conditions Load Turbocharger Temperature Idle Time (in minutes)
Before Shut Down
Stop & Go Empty Cool Less than 1
Stop & Go Medium Warm 1
Highway Speeds Medium Warm 2
City Traffic Max. GCWR Warm 3
Highway Speeds Max. GCWR Warm 4
Uphill Grade Max. GCWR Hot 5
282 STARTING AND OPERATING

ENGINE BLOCK HEATER Ð IF EQUIPPED
The engine block heater warms engine coolant and
permits quicker starts in cold weather. Connect the heater
cord to a ground-fault interrupter protected 110-115 volt
AC electrical outlet with a grounded, three-wire exten-
sion cord.
Use the heater when temperatures below 0ÉF (-18ÉC) are
expected to last for several days.
The block heater must be plugged in at least one hour to
have an adequate warming effect on the coolant.The engine block heater cord is located:²3.7L/4.7L Engine Ð coiled and strapped to the engine
oil dipstick tube.
²5.7L Engine Ð bundled and fastened to the injector
harness.
²3.0L Diesel Engine Ð on the passenger side of the
vehicle mounted on a stud between the fresh airbox
and coolant reservoir.
WARNING!
Remember to disconnect the cord before driving.
Damage to the 110-115 volt AC electrical cord could
cause electrocution.
STARTING AND OPERATING 283
5

AUTOMATIC TRANSMISSION
CAUTION!
Damage to the transmission may occur if the follow-
ing precautions are not observed:
²Shift into P (Park) only after the vehicle has come
to a complete stop.
²Shift into or out of R (Reverse) only after the
vehicle has come to a complete stop and the engine
is at idle speed.
²Do not shift from R (Reverse), P (Park), or N
(Neutral) into any forward gear when the engine is
above idle speed.
²Before shifting into any gear, make sure your foot
is firmly on the brake pedal.
WARNING!
It is dangerous to shift the selector lever out of P
(Park) or N (Neutral) if the engine speed is higher
than idle speed. If your foot is not firmly on the
brake pedal, the vehicle could accelerate quickly
forward or in reverse. You could lose control of the
vehicle and hit someone or something. Only shift
into gear when the engine is idling normally and
when your foot is firmly on the brake pedal.
Shift Lock Manual Override Ð If Equipped
Your vehicle may be equipped with a shift lock manual
override. The manual override may be used in the event
that the shift lever should fail to move from Park with the
key in the ON position and the brake pedal depressed. To
operate the shift lock manual override, perform the
following steps:
284 STARTING AND OPERATING

1. Firmly set the parking brake.
2. Using a flat blade screwdriver, carefully remove the
shift lock manual override cover which is located on the
PRNDL bezel.
3.
Depress and maintain firm pressure on the brake pedal.
4. Using the screwdriver, reach into the manual override
opening. Press and hold the shift lock lever down.5. Move the shift lever into the N (Neutral) position.
6. The vehicle may then be started in N (Neutral).
Have your vehicle inspected by your local authorized
dealer, if the shift lock manual override has been used.Brake/Transmission Interlock System
This system prevents you from moving the gear shift out
of P (Park) and into any gear unless the brake pedal is
pressed. This system is active only while the ignition
switch is in the ON position. Always depress thebrake
pedal first,before moving the gear selector out of P
(Park).
5±Speed Automatic Transmission
The electronically controlled transmission provides a
precise shift schedule. The transmission electronics are
self-calibrating; therefore, the first few shifts on a new
STARTING AND OPERATING 285
5

vehicle, may be somewhat abrupt. This is a normal
condition, and precision shifts will develop within a few
hundred miles.
Gear Ranges
NOTE:After selecting any gear range, wait a moment to
allow the selected gear to engage before accelerating.
This is especially important when the engine is cold. If
there is a need to restart the engine be sure to cycle the
key to the LOCK position before restarting. Transmission
gear engagement may be delayed after restarting the
engine if the key is not cycled to the LOCK position first.
P (Park)
This gear position supplements the parking brake by
locking the transmission. The engine can be started in
this range. Never use P (Park) while the vehicle is in
motion. Apply the parking brake when leaving the
vehicle in this range. Always apply parking brake first,
then place the selector in P (Park) position.
WARNING!
Never use P (Park) position as a substitute for the
parking brake. Always apply parking brake fully
when parked to guard against vehicle movement and
possible injury or damage.
WARNING!
It is dangerous to shift the selector lever out of P
(Park) or N (Neutral) if the engine speed is higher
than idle speed. If your foot is not firmly on the
brake pedal, the vehicle could accelerate quickly
forward or in reverse. You could lose control of the
vehicle and hit someone or something. Only shift
into gear when the engine is idling normally and
when your right foot is firmly on the brake pedal.
286 STARTING AND OPERATING

R (Reverse)
Use this range only after the vehicle has come to a
complete stop.
N (Neutral)
Shift into N (Neutral) when the vehicle is standing for
prolonged periods with the engine running. The engine
may be started in this range. Set the parking brake if you
must leave the vehicle.
NOTE:Towing the vehicle, coasting, or driving for any
other reason with selector lever in N (Neutral) can result
in severe transmission damage. Refer to ªRecreational
Towingº in Section 5 and ªTowing a Disabled Vehicleº in
Section 6 of this manual.
D (Drive)
Shift into D (Drive) only when the vehicle is at a complete
stop and the brakes are firmly applied. The transmissionautomatically upshifts through fifth gear. The D (Drive)
position provides optimum driving characteristics under
all normal operating conditions.
Electronic Range Select (ERS)Operation
The Electronic Range Select (ERS) shift control allows
you to move the shifter left (-) or right (+) when the
shifter is in the D (Drive) position, allowing the selection
of the desired top gear. For example, if the driver shifts
the transmission into 3 (third gear), the transmission will
never shift above third gear, but can shift down to 2
(second) or 1 (first), when needed.
When in the D (Drive) position, the first tap to the left (-),
will show the current gear. For example, if you are in D
(Drive) and are in 3rd gear, when you tap the gear shift
one time to the left (-), the display will show 3. Another
tap to the left (-) will shift the transmission into 2nd gear.
STARTING AND OPERATING 287
5

If you are in D (Drive) and are in 5th gear, the first tap to
the left (-) will display 5. Another tap to the left (-) will
shift the transmission into 4th gear.
On vehicles equipped with 4.7L or 5.7L engines, use of
ERS (or Tow/Haul mode) also enables a additional
underdrive gear which is not normally used during
through-gear accelerations. This additional gear im-
proves vehicle performance and cooling capability when
towing a trailer on certain grades. In ERS mode (on all
transmissions), 1st through 3rd gear are underdrive gears
and 4th gear is direct drive. ERS 5th gear (Overdrive) is
the same as the normal 4th gear.
WARNING!
Do not downshift for additional engine braking on a
slippery surface. The drive wheels could lose their
grip and the vehicle could skid.
Screen Display12345*D
Actual Gear(s)
Allowed1 1-2 1-3 1-4 1-5 1-5
* Applies to vehicles equipped with 4.7L/5.7L engines
only.
NOTE:To select the proper gear position for maximum
deceleration (engine braking), move the shift lever to the
left ªD(-)º and hold it there. The transmission will shift to
the range from which the vehicle can best be slowed
down.
Overdrive Operation
The automatic transmission includes an electronically
controlled Overdrive (5th gear for 3.7L engine, 4th and
5th gears for 4.7L and 5.7L engines). The transmission
will automatically shift from direct gear to Overdrive if
the following conditions are present:
288 STARTING AND OPERATING

²the transmission selector is in D (Drive);
²the engine coolant has reached normal operating tem-
perature;
²vehicle speed is above approximately 30 mph (48
km/h);
²the ªTOW/HAULº switch has not been activated;
²transmission has reached normal operating tempera-
ture.
NOTE:If the vehicle is started in extremely cold tem-
peratures, the transmission may not shift into Overdrive
and will automatically select the most desirable gear for
operation at this temperature. Normal operation will
resume when the transmission fluid temperature has
risen to a suitable level. Refer also to the Note under
torque converter clutch, later in this section.During cold temperature operation you may notice de-
layed upshifts depending on engine and transmission
temperature. This feature improves the warm up time of
the engine and transmission.
If the transmission temperature gets extremely hot, the
transmission will automatically select the most desirable
gear for operation at this temperature. If the transmission
temperature becomes hot enough, the ªTRANSMISSION
OVER TEMPº message may display and the transmis-
sion may downshift out of Overdrive until the transmis-
sion cools down. After cool down, the transmission will
resume normal operation.
In high ambient temperatures with sustained high engine
speed and load, an upshift followed shortly thereafter by
a downshift may occur. This is a normal part of the
overheat protection strategy when operating in the
ªTow/Haulº mode.
STARTING AND OPERATING 289
5

The transmission will downshift from Overdrive to the
most desirable gear if the accelerator pedal is fully
depressed at vehicle speeds above approximately 35 mph
(56 km/h).
When To Use ªTOW/HAULº Mode Ð If Equipped
When driving in hilly areas, towing a trailer, carrying a
heavy load, etc., and frequent transmission shifting oc-
curs, press the ªTOW/HAULº switch. This will improve
performance and reduce the potential for transmission
overheating or failure due to excessive shifting. When
operating in ªTOW/HAULº mode, the transmission will
shift to direct gear and Overdrive will be enabled under
steady cruise conditions.
The ªTOW/HAULº light will illuminate in the instru-
ment cluster to indicate when the switch has been
activated. Pressing the switch a second time restores
normal operation. If the ªTOW/HAULº mode is desired,
the switch must be pressed each time the engine is
started.
TOW/HAUL Switch
290 STARTING AND OPERATING