check engine light JEEP GRAND CHEROKEE 2002 WJ / 2.G Service Manual

position, the clutch will engage after the shift to
third gear, at approximately 56 km/h (35 mph) at
light throttle.
The TCM controls the torque converter by way of
internal logic software. The programming of the soft-
ware provides the TCM with control over the L/R-CC
Solenoid. There are four output logic states that can
be applied as follows:
²No EMCC
²Partial EMCC
²Full EMCC
²Gradual-to-no EMCC
NO EMCC
Under No EMCC conditions, the L/R Solenoid is
OFF. There are several conditions that can result in
NO EMCC operations. No EMCC can be initiated
due to a fault in the transmission or because the
TCM does not see the need for EMCC under current
driving conditions.
PARTIAL EMCC
Partial EMCC operation modulates the L/R Sole-
noid (duty cycle) to obtain partial torque converter
clutch application. Partial EMCC operation is main-
tained until Full EMCC is called for and actuated.
During Partial EMCC some slip does occur. Partial
EMCC will usually occur at low speeds, low load and
light throttle situations.
FULL EMCC
During Full EMCC operation, the TCM increases
the L/R Solenoid duty cycle to full ON after PartialEMCC control brings the engine speed within the
desired slip range of transmission input speed rela-
tive to engine rpm.
GRADUAL-TO-NO EMCC
This operation is to soften the change from Full or
Partial EMCC to No EMCC. This is done at mid-
throttle by decreasing the L/R Solenoid duty cycle.
REMOVAL
(1) Remove transmission and torque converter
from vehicle.
(2) Place a suitable drain pan under the converter
housing end of the transmission.
CAUTION: Verify that transmission is secure on the
lifting device or work surface, the center of gravity
of the transmission will shift when the torque con-
verter is removed creating an unstable condition.
The torque converter is a heavy unit. Use caution
when separating the torque converter from the
transmission.
(3) Pull the torque converter forward until the cen-
ter hub clears the oil pump seal.
(4) Separate the torque converter from the trans-
mission.
INSTALLATION
Check converter hub and drive flats for sharp
edges, burrs, scratches, or nicks. Polish the hub and
flats with 320/400 grit paper or crocus cloth if neces-
sary. Verify that the converter hub o-ring is properly
installed and is free from debris. The hub must be
smooth to avoid damaging the pump seal at installa-
tion.
(1) Lubricate oil pump seal lip with transmission
fluid.
(2) Place torque converter in position on transmis-
sion.
CAUTION: Do not damage oil pump seal or con-
verter hub o-ring while inserting torque converter
into the front of the transmission.
(3) Align torque converter to oil pump seal open-
ing.
(4) Insert torque converter hub into oil pump.
(5) While pushing torque converter inward, rotate
converter until converter is fully seated in the oil
pump gears.
(6) Check converter seating with a scale and
straightedge (Fig. 117). Surface of converter lugs
should be at least 13 mm (1/2 in.) to rear of straight-
edge when converter is fully seated.
(7) If necessary, temporarily secure converter with
C-clamp attached to the converter housing.
Fig. 116 Stator Operation
1 - DIRECTION STATOR WILL FREE WHEEL DUE TO OIL
PUSHING ON BACKSIDE OF VANES
2 - FRONT OF ENGINE
3 - INCREASED ANGLE AS OIL STRIKES VANES
4 - DIRECTION STATOR IS LOCKED UP DUE TO OIL PUSHING
AGAINST STATOR VANES
WJAUTOMATIC TRANSMISSION - 545RFE 21 - 269
TORQUE CONVERTER (Continued)

Pressure Diagnosis
Condition Possible Causes Correction
The low side pressure is
normal or slightly low, and
the high side pressure is too
low.1. Low refrigerant system
charge.1. See Plumbing/Diagnosis and Testing -
Refrigerant System Leaks in this group. Test the
refrigerant system for leaks. Repair, evacuate and
charge the refrigerant system, if required.
2. Refrigerant flow through
the accumulator is restricted.2. See Accumulator in this group. Replace the
restricted accumulator, if required.
3. Refrigerant flow through
the evaporator coil is
restricted.3. See A/C Evaporator in this group. Replace the
restricted evaporator coil, if required.
4. Faulty compressor. 4. See A/C Compressor in this group. Replace
the compressor, if required.
The low side pressure is
normal or slightly high, and
the high side pressure is too
high.1. Condenser air flow
restricted.1. Check the condenser for damaged fins, foreign
objects obstructing air flow through the condenser
fins, and missing or improperly installed air seals.
Refer to Cooling for more information on air
seals. Clean, repair, or replace components as
required.
2. Inoperative cooling fan. 2. Refer to Cooling for more information. Test the
cooling fan and replace, if required.
3. Refrigerant system
overcharged.3. See Plumbing/Standard Procedure -
Refrigerant System Charge in this group. Recover
the refrigerant from the refrigerant system.
Charge the refrigerant system to the proper level,
if required.
4. Air in the refrigerant
system.4. See Plumbing/Diagnosis and Testing -
Refrigerant System Leaks in this group. Test the
refrigerant system for leaks. Repair, evacuate and
charge the refrigerant system, if required.
5. Engine overheating. 5. Refer to Cooling for more information. Test the
cooling system and repair, if required.
The low side pressure is too
high, and the high side
pressure is too low.1. Accessory drive belt
slipping.1. Refer to Cooling for more information. Inspect
the accessory drive belt condition and tension.
Tighten or replace the accessory drive belt, if
required.
2. Faulty compressor. 2. See A/C Compressor in this group. Replace
the compressor, if required.
The low side pressure is too
low, and the high side
pressure is too high.1. Restricted refrigerant flow
through the refrigerant lines.1. See Liquid, Suction, and Discharge Line in this
group. Inspect the refrigerant lines for kinks, tight
bends or improper routing. Correct the routing or
replace the refrigerant line, if required.
2. Restricted refrigerant flow
through the a/c expansion
valve.2. See A/C Expansion Valve in this group.
Replace the Expansion Valve if restricted.
3. Restricted refrigerant flow
through the condenser.3. See A/C Condenser in this group. Replace the
restricted condenser, if required.
WJHEATING & AIR CONDITIONING 24 - 5
HEATING & AIR CONDITIONING (Continued)

DIAGNOSIS AND TESTING - HEATER
PERFORMANCE
Before performing the following tests, refer to Cool-
ing for the procedures to check the radiator coolant
level, serpentine drive belt tension, radiator air flow
and the radiator fan operation. Also be certain that
the accessory vacuum supply line is connected at the
engine intake manifold for the manual temperature
control system.
MAXIMUM HEATER OUTPUT
Engine coolant is delivered to the heater core
through two heater hoses. With the engine idling at
normal operating temperature, set the temperature
control knob in the full hot position, the mode control
switch knob in the floor heat position, and the blower
motor switch knob in the highest speed position.
Using a test thermometer, check the temperature of
the air being discharged at the HVAC housing floor
outlets. Compare the test thermometer reading to the
Temperature Reference chart.
Temperature Reference
Ambient Air Temperature15.5É C
(60É F)21.1É C
(70É F)26.6É C
(80É F)32.2É C
(90É F)
Minimum Air Temperature at
Floor Outlet62.2É C
(144É F)63.8É C
(147É F)65.5É C
(150É F)67.2É C
(153É F)
If the floor outlet air temperature is too low, refer
to Cooling to check the engine coolant temperature
specifications. Both of the heater hoses should be hot
to the touch. The coolant return heater hose should
be slightly cooler than the coolant supply heater
hose. If the return hose is much cooler than the sup-
ply hose, locate and repair the engine coolant flow
obstruction in the cooling system. Refer to Cooling
for the procedures.
OBSTRUCTED COOLANT FLOW
Possible locations or causes of obstructed coolant
flow:
²Pinched or kinked heater hoses.
²Improper heater hose routing.
²Plugged heater hoses or supply and return ports
at the cooling system connections.
²A plugged heater core.
If proper coolant flow through the cooling system is
verified, and heater outlet air temperature is still
low, a mechanical problem may exist.
MECHANICAL PROBLEMS
Possible locations or causes of insufficient heat:
²An obstructed cowl air intake.
²Obstructed heater system outlets.
²A blend door not functioning properly.
TEMPERATURE CONTROL
If the heater outlet air temperature cannot be
adjusted with the temperature control knob(s) on the
A/C Heater control panel, the following could require
service:
²The A/C heater control.
²The blend door actuator(s).
²The wire harness circuits for the A/C heater con-
trol or the blend door actuator(s).²The blend door(s).
²Improper engine coolant temperature.
STANDARD PROCEDURE - DIODE
REPLACEMENT
(1) Disconnect and isolate the negative battery
cable.
(2) Locate the diode in the harness, and remove
the protective covering.
(3) Remove the diode from the harness, pay atten-
tion to the current flow direction (Fig. 3).
(4) Remove the insulation from the wires in the
harness. Only remove enough insulation to solder in
the new diode.
Fig. 3 DIODE IDENTIFICATION
1 - CURRENT FLOW
2 - BAND AROUND DIODE INDICATES CURRENT FLOW
3 - DIODE AS SHOWN IN THE DIAGRAMS
24 - 6 HEATING & AIR CONDITIONINGWJ
HEATING & AIR CONDITIONING (Continued)

INSTALLATION
INSTALLATION - RECIRCULATION DOOR
VACUUM ACTUATOR
(1) Install the recirculation door vacuum actuator
on the HVAC housing and tighten the mounting
screws to 2.2 N´m (20 in. lbs.).
(2) Engage the recirculation door actuating rod
with the recirculation door lever.
(3) Engage the recirculation door pivot connection
with the door pivot pin.
(4) Plug in the vacuum harness connector to the
recirculation door vacuum actuator.
(5) Install the instrument panel in the vehicle.
Refer to Instrument Panel System for the procedures.
INSTALLATION - RECIRCULATION DOOR
ELECTRIC ACTUATOR
(1) Install the recirculation door actuator on the
recirculation door housing and tighten the mounting
screws to 2.2 N´m (20 in. lbs.).
(2) Install the recirculation door housing on the
HVAC unit and tighten the mounting screws to 2.2
N´m (20 in. lbs.).
(3) Plug in the wire harness connector to the recir-
culation door actuator.
(4) Install the instrument panel in the vehicle.
Refer to Instrument Panel System for the procedures.
VACUUM CHECK VALVE
DESCRIPTION
Two vacuum check valves (non AZC only) are
installed on the vacuum supply system. One is on the
accessory vacuum supply line in the engine compart-
ment, near the vacuum tap on the engine intake
manifold. A second vacuum check valve is located on
the bottom of the HVAC unit behind the passenger
front floor duct on the black vacuum line. The vac-
uum check valves are designed to allow vacuum to
flow in only one direction through the accessory vac-
uum supply circuits.
OPERATION
The use of a vacuum check valve helps to maintain
the system vacuum needed to retain the selected A/C
Heater mode settings. The check valve will prevent
the engine from bleeding down system vacuum
through the intake manifold during extended heavy
engine load (low engine vacuum) operation.
The vacuum check valve cannot be repaired and, if
faulty or damaged, it must be replaced.
REMOVAL
(1) Unplug the HVAC vacuum supply line connec-
tor at the vacuum check valve near the engine intake
manifold vacuum adapter fitting.
(2) Note the orientation of the check valve in the
vacuum supply line for correct installation.
(3) Unplug the vacuum check valve from the vac-
uum supply line fittings.
INSTALLATION
(1) Plug in the vacuum check valve at the vacuum
supply line fittings, noting the orientation of the
check valve in the vacuum supply line for correct
installation.
(2) Plug in the HVAC vacuum supply line connec-
tor at the vacuum check valve near the engine intake
manifold vacuum adapter fitting.
VACUUM RESERVOIR
DESCRIPTION
The vacuum reservoir is mounted in the right front
of the vehicle behind the headlamp mounting module
(Fig. 22). The headlamp mounting module and head-
lamp assembly must be removed from the vehicle to
access the vacuum reservoir for service. Refer to
Lamps/Lighting for the procedures.
OPERATION
Engine vacuum is stored in the vacuum reservoir.
The stored vacuum is used to operate the vacuum-
Fig. 21 RECIRCULATION DOOR HOUSING
1 - RECIRCULATION DOOR HOUSING
2 - ATTACHING SCREWS
24 - 34 CONTROLSWJ
RECIRCULATION DOOR ACTUATOR (Continued)

CCV HOSE
DIAGNOSIS AND TESTING - CCV SYSTEM -
4.0L
Before attempting diagnosis, be sure locations of
fixed orifice fitting and air inlet fitting (Fig. 8) have
not been inadvertently exchanged. The fixed orifice
fitting is light grey in color and is located atrearof
valve cover. The air inlet fitting is black in color and
is located atfrontof valve cover.
(1) Pull fixed orifice fitting (Fig. 8) from valve
cover and leave tube attached.
(2) Start engine and bring to idle speed.
(3) If fitting is not plugged, a hissing noise will be
heard as air passes through fitting orifice. Also, a
strong vacuum should be felt with a finger placed at
fitting inlet.
(4) If vacuum is not present, remove fitting orifice
fitting from tube. Start engine. If vacuum can now be
felt, replace fixed orifice fitting. Do not attempt to
clean plastic fitting.
(5) If vacuum is still not felt at hose, check line/
hose for kinks or for obstruction. If necessary, clean
out intake manifold fitting at intake manifold. Do
this by turning a 1/4 inch drill (by hand) through the
fitting to dislodge any solid particles. Blow out thefitting with shop air. If necessary, use a smaller drill
to avoid removing any metal from the fitting.
(6) Return fixed orifice fitting to valve cover and
leave tube attached.
(7) Disconnect air inlet fitting and its attached
hose at front of valve cover (Fig. 8). Start engine and
bring to idle speed. Hold a piece of stiff paper (such
as a parts tag) loosely over the rubber grommet
(opening) of the disconnected air inlet fitting.
(8) The paper should be drawn against the rubber
grommet with noticeable force. This will be after
allowing approximately one minute for crankcase
pressure to reduce.
(9) If vacuum is not present, check breather hoses/
tubes/lines for obstructions or restrictions.
(10) After testing, reconnect all system hoses/
tubes/lines.
REMOVAL - FIXED ORIFICE FITTING
When installing fixed orifice fitting, be sure loca-
tions of fixed orifice fitting and air inlet fitting (Fig.
9) have not been inadvertently exchanged. The fixed
orifice fitting is light grey in color and is located at
rearof valve cover. The air inlet fitting is black in
color and is located atfrontof valve cover.
(1) Pull fixed orifice fitting (Fig. 9) from valve
cover grommet.
(2) Separate fitting from CCV breather tube.
Fig. 8 Fixed Orifice Fitting and CCV SystemÐ4.0L
Engine
1 - AIR INLET FITTING
2 - FIXED ORIFICE FITTING
3 - CCV BREATHER TUBE (REAR)
4 - INT. MAN. FITTING
5 - CCV BREATHER TUBE (FRONT)
Fig. 9 FIXED ORIFICE FITTING - 4.0L
1 - AIR INLET FITTING
2 - FIXED ORIFICE FITTING
3 - CCV BREATHER TUBE (REAR)
4 - INT. MAN. FITTING
5 - CCV BREATHER TUBE (FRONT)
25 - 28 EVAPORATIVE EMISSIONSWJ

change from opened to closed. If the reed switch
changes too quickly, a leak may be indicated. The
longer it takes the reed switch to change state, the
tighter the evaporative system is sealed. If the sys-
tem pressurizes too quickly, a restriction somewhere
in the EVAP system may be indicated.
PUMPING ACTION
Action : During portions of this test, the PCM uses
the reed switch to monitor diaphragm movement.
The solenoid is only turned on by the PCM after the
reed switch changes from open to closed, indicating
that the diaphragm has moved down. At other times
during the test, the PCM will rapidly cycle the LDP
solenoid on and off to quickly pressurize the system.
During rapid cycling, the diaphragm will not move
enough to change the reed switch state. In the state
of rapid cycling, the PCM will use a fixed time inter-
val to cycle the solenoid. If the system does not pass
the EVAP Leak Detection Test, the following DTCs
may be set:
²P0442 - EVAP LEAK MONITOR 0.0409LEAK
DETECTED
²P0455 - EVAP LEAK MONITOR LARGE LEAK
DETECTED²P0456 - EVAP LEAK MONITOR 0.0209LEAK
DETECTED
²P1486 - EVAP LEAK MON PINCHED HOSE
FOUND
²P1494 - LEAK DETECTION PUMP SW OR
MECH FAULT
²P1495 - LEAK DETECTION PUMP SOLENOID
CIRCUIT
DIAGNOSIS AND TESTING - ENABLING
CONDITIONS TO RUN EVAP LEAK DETECTION
TEST
²Cold start: with ambient temperature (obtained
from modeling the inlet air temperature sensor on
passenger vehicles and the battery temperature sen-
sor on Jeep & Dodge Truck vehicles) between 4É C
(40É F) and 32É C (90É F) for 0.040 leak. Between 4É
C (40É F) and 29É C (85É F) for 0.020 leak.
²Engine coolant temperature within:-12É to -8É C
(10É to 18É F) of battery/ambient.
²Battery voltage between 10 and 15 volts.
²Low fuel warning light off (fuel level must be
between 15% and 85%.
²MAP sensor reading 22 in Hg or above (This is
the manifold absolute pressure, not vacuum).
Fig. 13 LDP AT REST
1 - Diaphragm
2 - Inlet Check Valve (Closed)
3 - Vent Valve (Open)
4 - From Air Filter
5 - To Canister
6 - Outlet Check Valve (Closed)
7 - Engine Vacuum (Closed)
Fig. 14 DIAPHRAGM UPWARD MOVEMENT
1 - Diaphragm
2 - Inlet Check Valve (Open)
3 - Vent Valve (Closed)
4 - From Air Filter
5 - To Canister
6 - Outlet Check Valve (Closed)
7 - Engine Vacuum (Open)
25 - 32 EVAPORATIVE EMISSIONSWJ
LEAK DETECTION PUMP (Continued)

(8)Do not attempt to clean the old PCV valve.
(9) Return PCV valve back to oil filler tube by
placing valve locating tabs (Fig. 21) into cam lock.
Press PCV valve in and rotate valve upward. A slight
click will be felt when tabs have engaged cam lock.
Valve should be pointed towards rear of vehicle.
(10) Connect PCV line/hose and connecting rubber
hose to PCV valve.
(11) Disconnect rubber hose from fresh air fitting
at left side of air cleaner resonator box (Fig. 22).
Start engine and bring to idle speed. Hold a piece of
stiff paper (such as a parts tag) loosely over the
opening of the disconnected rubber hose.
(12) The paper should be drawn against the hose
opening with noticeable force. This will be after
allowing approximately one minute for crankcase
pressure to reduce.
(13) If vacuum is not present, disconnect each PCV
system hose at top of each breather (Fig. 22). Check
for obstructions or restrictions.(14) If vacuum is still not present, remove each
PCV system breather (Fig. 22) from each cylinder
head. Check for obstructions or restrictions. If
plugged, replace breather. Tighten breather to 12
N´m (106 in. lbs.) torque. Do not attempt to clean
breather
(15) If vacuum is still not present, disconnect each
PCV system hose at each fitting and check for
obstructions or restrictions.
Fig. 21 PCV Valve/Oil Filler TubeÐ4.7L V-8 Engine
1 - O-RING
2 - LOCATING TABS
3 - CAM LOCK
4 - OIL FILLER TUBE
5 - PCV LINE/HOSE
6 - P C V VA LV E
Fig. 22 PCV Breathers/Tubes/HosesÐ4.7L V-8
Engine
1 - FRESH AIR FITTING
2 - CONNECTING TUBES/HOSES
3 - CRANKCASE BREATHERS (2)
4 - RUBBER HOSE
5 - AIR CLEANER RESONATOR
25 - 38 EVAPORATIVE EMISSIONSWJ
PCV VALVE (Continued)

REMOVAL - PCV VALVE - 4.7L
The PCV valve is located on the oil filler tube (Fig.
23). Two locating tabs are located on the side of the
valve (Fig. 23). These 2 tabs fit into a cam lock in the
oil filler tube. An o-ring seals the valve to the filler
tube.
(1) Disconnect PCV line/hose (Fig. 23) by discon-
necting rubber hose at PCV valve fitting.
(2) Remove PCV valve at oil filler tube by rotating
PCV valve downward (counter-clockwise) until locat-
ing tabs have been freed at cam lock (Fig. 23). After
tabs have cleared, pull valve straight out from filler
tube.To prevent damage to PCV valve locating
tabs, valve must be pointed downward for
removal. Do not force valve from oil filler tube.
(3) After valve is removed, check condition of valve
o-ring (Fig. 23).
INSTALLATION - PCV VALVE - 4.7L
The PCV valve is located on the oil filler tube (Fig.
23). Two locating tabs are located on the side of the
valve (Fig. 23). These 2 tabs fit into a cam lock in the
oil filler tube. An o-ring seals the valve to the filler
tube.
(1) Return PCV valve back to oil filler tube by
placing valve locating tabs (Fig. 23) into cam lock.
Press PCV valve in and rotate valve upward. A slight
click will be felt when tabs have engaged cam lock.
Valve should be pointed towards rear of vehicle.
(2) Connect PCV line/hose and rubber hose to PCV
valve.
VACUUM LINES
DESCRIPTION
A vacuum schematic for emission related items can
be found on the VECI label. Refer to Vehicle Emis-
sion Control Information (VECI) Label for label loca-
tion.
VAPOR CANISTER
DESCRIPTION
A maintenance free, EVAP canister is used on all
gasoline powered models. The canister is attached to
a two-piece support bracket located behind the left-
rear wheel.
OPERATION
The EVAP canister is filled with granules of an
activated carbon mixture. Fuel vapors entering the
EVAP canister are absorbed by the charcoal granules.
The canister serves two functions: as a temporary
fuel vapor storage point while refueling the vehicle
for the ORVR system, as a temporary vapor storage
point while the engine is running.
Fuel tank pressure vents into the EVAP canister.
Fuel vapors are temporarily held in the canister until
they can be drawn into the intake manifold. The duty
cycle EVAP canister purge solenoid allows the EVAP
canister to be purged at predetermined times and at
certain engine operating conditions.
Refer to ORVR for additional information.
Fig. 23 PCV Valve/Oil Filler Tube Location
1 - O-RING
2 - LOCATING TABS
3 - CAM LOCK
4 - OIL FILLER TUBE
5 - PCV LINE/HOSE
6 - P C V VA LV E
WJEVAPORATIVE EMISSIONS 25 - 39
PCV VALVE (Continued)