2002 JEEP LIBERTY check engine light

(7) Crank engine until maximum pressure is
reached on gage. Record this pressure as #1 cylinder
pressure.
(8) Repeat the previous step for all remaining cyl-
inders.
(9) Compression should not be less than 689 kPa
(100 psi) and not vary more than 25 percent from cyl-
inder to cylinder.
(10) If one or more cylinders have abnormally low
compression pressures, repeat the compression test.
(11) If the same cylinder or cylinders repeat an
abnormally low reading on the second compression
test, it could indicate the existence of a problem in
the cylinder in question.The recommended com-
pression pressures are to be used only as a
guide to diagnosing engine problems. An engine
should not be disassembled to determine the
cause of low compression unless some malfunc-
tion is present.
DIAGNOSIS AND TESTING - ENGINE OIL LEAK
INSPECTION
Begin with a thorough visual inspection of the
engine, particularly at the area of the suspected leak.
If an oil leak source is not readily identifiable, the
following steps should be followed:
(1) Do not clean or degrease the engine at this
time because some solvents may cause rubber to
swell, temporarily stopping the leak.
(2) Add an oil soluble dye (use as recommended by
manufacturer). Start the engine and let idle for
approximately 15 minutes. Check the oil dipstick to
make sure the dye is thoroughly mixed as indicated
with a bright yellow color under a black light.
(3) Using a black light, inspect the entire engine
for fluorescent dye, particularly at the suspected area
of oil leak. If the oil leak is found and identified,
repair as necessary.
(4) If dye is not observed, drive the vehicle at var-
ious speeds for approximately 24 km (15 miles), and
repeat inspection.
(5)If the oil leak source is not positively
identified at this time, proceed with the air leak
detection test method as follows:
²Disconnect the fresh air hose (make-up air) at
the cylinder head cover and plug or cap the nipple on
the cover.
²Remove the PCV valve hose from the cylinder
head cover. Cap or plug the PCV valve nipple on the
cover.
²Attach an air hose with pressure gauge and reg-
ulator to the dipstick tube.
CAUTION: Do not subject the engine assembly to
more than 20.6 kpa (3 PSI) of test pressure.²Gradually apply air pressure from 1 psi to 2.5
psi maximum while applying soapy water at the sus-
pected source. Adjust the regulator to the suitable
test pressure that provides the best bubbles which
will pinpoint the leak source. If the oil leak is
detected and identified, repair per service manual
procedures.
²If the leakage occurs at the crankshaft rear oil
seal area, refer to the section, Inspection for Rear
Seal Area Leak.
(6) If no leaks are detected, turn off the air supply.
Remove the air hose, all plugs, and caps. Install the
PCV valve and fresh air hose (make-up air). Proceed
to next step.
(7) Clean the oil off the suspect oil leak area using
a suitable solvent. Drive the vehicle at various
speeds approximately 24 km (15 miles). Inspect the
engine for signs of an oil leak by using a black light.
NOTE: If oil leakage is observed at the dipstick tube
to block location; remove the tube, clean and reseal
using MoparTStud & Bearing Mount (press fit tube
applications only), and for O-ring style tubes,
remove tube and replace the O-ring seal.
INSPECTION FOR REAR SEAL AREA LEAKS
Since it is sometimes difficult to determine the
source of an oil leak in the rear seal area of the
engine, a more involved inspection is necessary. The
following steps should be followed to help pinpoint
the source of the leak.
If the leakage occurs at the crankshaft rear oil seal
area:
(1) Disconnect the battery.
(2) Raise the vehicle.
(3) Remove torque converter or clutch housing
cover and inspect rear of block for evidence of oil.
Use a black light to check for the oil leak. If a leak is
present in this area, remove transmission for further
inspection.
(a) Circular spray pattern generally indicates
seal leakage or crankshaft damage.
(b) Where leakage tends to run straight down,
possible causes are a porous block, oil gallery cup
plug, bedplate to cylinder block mating surfaces
and seal bore. See proper repair procedures for
these items.
(4) If no leaks are detected, pressurize the crank-
case as previously described.
CAUTION: Do not exceed 20.6 kPa (3 psi).
(5) If the leak is not detected, very slowly turn the
crankshaft and watch for leakage. If a leak is
detected between the crankshaft and seal while
slowly turning the crankshaft, it is possible the
9s - 4 ENGINEKJ
ENGINE - 2.4L (Continued)

crankshaft seal surface is damaged. The seal area on
the crankshaft could have minor nicks or scratches
that can be polished out with emery cloth.
CAUTION: Use extreme caution when crankshaft
polishing is necessary to remove minor nicks and
scratches. The crankshaft seal flange is especially
machined to complement the function of the rear oil
seal.
(6) For bubbles that remain steady with shaft
rotation, no further inspection can be done until dis-
assembled.
(7) After the oil leak root cause and appropriate
corrective action have been identified, replace compo-
nent(s) as necessary.
DIAGNOSIS AND TESTING - ENGINE
Engine diagnosis is helpful in determining the
causes of malfunctions not detected and remedied by
routine maintenance.
These malfunctions may be classified as either
mechanical (e.g., a strange noise), or performance
(e.g., engine idles rough and stalls).Refer to the Engine Mechanical and the Engine
Performance diagnostic charts, for possible causes
and corrections of malfunctions (Refer to 9 - ENGINE
- DIAGNOSIS AND TESTING - MECHANICAL)
(Refer to 9 - ENGINE - DIAGNOSIS AND TESTING
- PERFORMANCE).
For fuel system diagnosis, (Refer to 14 - FUEL
SYSTEM/FUEL DELIVERY - DIAGNOSIS AND
TESTING).
Additional tests and diagnostic procedures may be
necessary for specific engine malfunctions that can-
not be isolated with the Service Diagnosis charts.
Information concerning additional tests and diagno-
sis is provided within the following:
²Cylinder Compression Pressure Test
²Cylinder Combustion Pressure Leakage Test
²Engine Cylinder Head Gasket Failure Diagnosis
²Intake Manifold Leakage Diagnosis
²Lash Adjuster (Tappet) Noise Diagnosis
²Engine Oil Leak Inspection
DIAGNOSIS AND TESTING - ENGINE DIAGNOSIS - PERFORMANCE
CONDITION POSSIBLE CAUSE CORRECTION
ENGINE WILL NOT START 1. Weak battery. 1. Test battery. Charge or replace
as necessary. (Refer to 8 -
ELECTRICAL/BATTERY SYSTEM -
DIAGNOSIS AND TESTING)
2. Corroded or loose battery
connections.2. Clean and tighten battery
connections. Apply a coat of light
mineral grease to terminals.
3. Faulty starter. 3. Test starting system. (Refer to 8 -
ELECTRICAL/STARTING -
DIAGNOSIS AND TESTING)
4. Faulty coil(s) or control unit. 4. Test and replace as needed.
(Refer to Appropriate Diagnostic
Information)
5. Incorrect spark plug gap. 5. Set gap. (Refer to 8 -
ELECTRICAL/IGNITION CONTROL
- SPECIFICATIONS)
6. Contamination in fuel system. 6. Clean system and replace fuel
filter.
7. Faulty fuel pump. 7. Test fuel pump and replace as
needed. (Refer to Appropriate
Diagnostic Information)
8. Incorrect engine timing. 8. Check for a skipped timing
belt/chain.
KJENGINE9s-5
ENGINE - 2.4L (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
OIL CONSUMPTION OR SPARK
PLUGS FOULED1. PCV system malfunction. 1. Check system and repair as
necessary. (Refer to 25 -
EMISSIONS CONTROL/
EVAPORATIVE EMISSIONS/PCV
VALVE - DIAGNOSIS AND
TESTING)
2. Worn, scuffed or broken rings. 2. Hone cylinder bores. Install new
rings.
3. Carbon in oil ring slots. 3. Install new rings.
4. Rings fitted too tightly in grooves. 4. Remove rings and check
grooves. If groove is not proper
width, replace piston.
5. Worn valve guide(s). 5. Replace cylinder head assembly.
6. Valve stem seal(s) worn or
damaged.6. Replace seal(s).
STANDARD PROCEDURE
STANDARD PROCEDURE - ENGINE CORE AND
OIL GALLERY PLUGS
Using a blunt tool such as a drift and a hammer,
strike the bottom edge of the cup plug. With the cup
plug rotated, grasp firmly with pliers or other suit-
able tool and remove plug (Fig. 2).
CAUTION: Do not drive cup plug into the casting as
restricted cooling can result and cause serious
engine problems.Thoroughly clean inside of cup plug hole in cylin-
der block or head. Be sure to remove old sealer.
Lightly coat inside of cup plug hole with Mopart
Stud and Bearing Mount. Make certain the new plug
is cleaned of all oil or grease. Using proper drive
plug, drive plug into hole so that the sharp edge of
the plug is at least 0.5 mm (0.020 in.) inside the
lead-in chamfer.
It is not necessary to wait for curing of the sealant.
The cooling system can be refilled and the vehicle
placed in service immediately.
STANDARD PROCEDURE - REPAIR OF
DAMAGED OR WORN THREADS
Damaged or worn threads (excluding spark plug
and camshaft bearing cap attaching threads) can be
repaired. Essentially, this repair consists of drilling
out worn or damaged threads, tapping the hole with
a special Heli-Coil Tap, (or equivalent) and installing
an insert into the tapped hole. This brings the hole
back to its original thread size.
CAUTION: Be sure that the tapped holes maintain
the original center line.
Heli-Coil tools and inserts are readily available
from automotive parts jobbers.
STANDARD PROCEDURE - HYDROSTATIC
LOCKED ENGINE
When an engine is suspected to be hydrostatically
locked, regardless of what caused the problem, the
following steps should be used.
CAUTION: DO NOT use starter motor to rotate the
engine, severe damage may occur.
Fig. 2 Core Hole Plug Removal
1 - CYLINDER BLOCK
2 - REMOVE PLUG WITH PLIERS
3 - STRIKE HERE WITH HAMMER
4 - DRIFT PUNCH
5 - CUP PLUG
KJENGINE9s-9
ENGINE - 2.4L (Continued)

shown in (Fig. 34). Refer to for Engine Specifications
(Refer to 9 - ENGINE - SPECIFICATIONS). Correct
piston to bore clearance must be established in order
to assure quiet and economical operation.
NOTE: Pistons and cylinder bores should be mea-
sured at normal room temperature, 21ÉC (70ÉF).
STANDARD PROCEDURE - CYLINDER BORE
HONING
(1) Used carefully, the cylinder bore resizing hone,
recommended tool C-823 or equivalent, equipped
with 220 grit stones, is the best tool for this honing
procedure. In addition to deglazing, it will reduce
taper and out-of-round as well as removing light
scuffing, scoring or scratches. Usually a few strokes
will clean up a bore and maintain the required lim-
its.
(2) Deglazing of the cylinder walls may be done
using a cylinder surfacing hone, recommended toolC-3501 or equivalent, equipped with 280 grit stones,
if the cylinder bore is straight and round. 20±60
strokes depending on the bore condition, will be suf-
ficient to provide a satisfactory surface. Use a light
honing oil.Do not use engine or transmission oil,
mineral spirits or kerosene.Inspect cylinder walls
after each 20 strokes.
(3) Honing should be done by moving the hone up
and down fast enough to get a cross-hatch pattern.
When hone marksintersectat 40-60 degrees, the
cross hatch angle is most satisfactory for proper seat-
ing of rings (Fig. 36).
(4) A controlled hone motor speed between
200±300 RPM is necessary to obtain the proper cross-
hatch angle. The number of up and down strokes per
minute can be regulated to get the desired 40±60
degree angle. Faster up and down strokes increase
the cross-hatch angle.
(5) After honing, it is necessary that the block be
cleaned again to remove all traces of abrasive.
CAUTION: Ensure all abrasives are removed from
engine parts after honing. It is recommended that a
solution of soap and hot water be used with a
brush and the parts then thoroughly dried. The bore
can be considered clean when it can be wiped
clean with a white cloth and cloth remains clean.
Oil the bores after cleaning to prevent rusting.
CLEANING
Clean cylinder block thoroughly using a suitable
cleaning solvent.
Fig. 34 Checking Cylinder Bore -Typical
Fig. 35 Piston Measurement - Typical
Fig. 36 Cylinder Bore Cross-Hatch Pattern
1 - CROSS-HATCH PATTERN
2 - 40ɱ60É
KJENGINE9s-31
ENGINE BLOCK (Continued)

(1) Remove protective cap at fuel rail test port.
Connect the 0±414 kPa (0-60 psi) fuel pressure gauge
(from gauge set 5069) to test port pressure fitting on
fuel rail (Fig. 20).The DRBtIII Scan Tool along
with the PEP module, the 500 psi pressure
transducer, and the transducer-to-test port
adapter may also be used in place of the fuel
pressure gauge.
(2) Start and warm engine and note pressure
gauge reading. Fuel pressure should be 339 kPa   34
kPa (49.2 psi   5 psi) at idle.
(3) If engine runs, but pressure is below 44.2 psi,
check for a kinked fuel supply line somewhere
between fuel rail and fuel pump module. If line is not
kinked, but specifications for either the Fuel Pump
Capacity, Fuel Pump Amperage or Fuel Pressure
Leak Down Tests were not met, replace lower section
of fuel pump module. Refer to Fuel Pump Module
Removal/Installation.
(4) If operating pressure is above 54.2 psi, electric
fuel pump is OK, but fuel pressure regulator is defec-
tive. Replace lower section of fuel pump module.
Refer to Fuel Pump Module Removal/Installation.
(5) Install protective cap to fuel rail test port.
DIAGNOSIS AND TESTING - FUEL PUMP
AMPERAGE TEST
This amperage (current draw) test is to be done in
conjunction with the Fuel Pump Pressure Test, Fuel
Pump Capacity Test and Fuel Pressure Leak Down
Test. Before performing the amperage test, be sure
the temperature of the fuel tank is above 50É F (10É
C).The DRBtScan Tool along with the DRB Low Cur-
rent Shunt (LCS) adapter (Fig. 21) and its test leads
will be used to check fuel pump amperage specifica-
tions.
(1) Be sure fuel tank contains fuel before starting
test. If tank is empty or near empty, amperage read-
ings will be incorrect.
(2) Obtain LCS adapter.
(3) Plug cable from LCS adapter into DRB scan
tool at SET 1 receptacle.
(4) Plug DRB into vehicle 16±way connector (data
link connector).
(5) Connect (-) and (+) test cable leads into LCS
adapter receptacles. Use10 amp (10A +)receptacle
and common (-) receptacles.
(6) Gain access to MAIN MENU on DRB screen.
(7) Press DVOM button on DRB.
(8) Using left/right arrow keys, highlight CHAN-
NEL 1 function on DRB screen.
(9) Press ENTER three times.
(10) Using up/down arrow keys, highlight RANGE
on DRB screen (screen will default to 2 amp scale).
(11) Press ENTER to change 2 amp scale to 10
amp scale.This step must be done to prevent
damage to DRB scan tool or LCS adapter
(blown fuse).
(12) Remove cover from Power Distribution Center
(PDC).
(13) Remove fuel pump relay from PDC. Refer to
label on PDC cover for relay location.
Fig. 20 FUEL PRESSURE TEST GAUGE (TYPICAL
GAUGE INSTALLATION AT TEST PORT)
1 - SERVICE (TEST) PORT
2 - FUEL PRESSURE TEST GAUGE
3 - FUEL RAIL
Fig. 21 LOW CURRENT SHUNT
1 - LOW CURRENT SHUNT ADAPTER
2 - PLUG TO DRB
3 - TEST LEAD RECEPTACLES
14 - 16 FUEL DELIVERYKJ
FUEL PUMP (Continued)

(14) If fuel injectors are to be removed, refer to
Fuel Injector Removal/Installation.
INSTALLATION
2.4L Engine
(1) If fuel injectors are to be installed, refer to Fuel
Injector Removal/Installation.
(2) Clean out fuel injector machined bores in
intake manifold.
(3) Apply a small amount of engine oil to each fuel
injector o-ring. This will help in fuel rail installation.
(4) Position fuel rail/fuel injector assembly to
machined injector openings in intake manifold.
(5) Guide each injector into cylinder head. Be care-
ful not to tear injector o-rings.
(6) Push fuel rail down until fuel injectors have
bottomed on shoulders.
(7) Install 2 fuel rail mounting bolts and tighten.
Refer to torque specifications.
(8) Connect electrical connectors at all fuel injec-
tors. To install connector, refer to (Fig. 37). Push con-
nector onto injector (1) and then push and lock red
colored slider (2). Verify connector is locked to injec-
tor by lightly tugging on connector.
(9) Snap 2 injection wiring harness clips (Fig. 35)
into brackets.
(10) Connect 2 main engine harness connectors at
rear of intake manifold (Fig. 34).
(11) Tighten 5 intake manifold mounting bolts.
Refer to Engine Torque Specifications.
(12) Install PCV valve and hose.
(13) Install thermostat and radiator hose. Fill with
coolant. Refer to Cooling.
(14) Connect necessary vacuum lines to throttle
body.
(15) Connect fuel line latch clip and fuel line to
fuel rail. Refer to Quick-Connect Fittings.
(16) Install air duct to throttle body.
(17) Connect battery cable to battery.
(18) Start engine and check for leaks.
3.7L Engine
(1) If fuel injectors are to be installed, refer to Fuel
Injector Removal/Installation.
(2) Clean out fuel injector machined bores in
intake manifold.
(3) Apply a small amount of engine oil to each fuel
injector o-ring. This will help in fuel rail installation.
(4) Position fuel rail/fuel injector assembly to
machined injector openings in cylinder head.
(5) Guide each injector into cylinder head. Be care-
ful not to tear injector o-rings.
(6) Pushrightside of fuel rail down until fuel
injectors have bottomed on cylinder head shoulder.Pushleftfuel rail down until injectors have bot-
tomed on cylinder head shoulder.
(7) Install 4 fuel rail mounting bolts and tighten.
Refer to torque specifications.
(8) Install 6 ignition coils. Refer to Ignition Coil
Removal/Installation.
(9) Connect electrical connectors to throttle body.
(10) Connect electrical connectors at all fuel injec-
tors. To install connector, refer to (Fig. 37). Push con-
nector onto injector (1) and then push and lock red
colored slider (2). Verify connector is locked to injec-
tor by lightly tugging on connector.
(11) Connect necessary vacuum lines to throttle
body.
(12) Connect fuel line latch clip and fuel line to
fuel rail. Refer to Quick-Connect Fittings.
(13) Install air box to throttle body.
(14) Install air duct to air box.
(15) Connect battery cable to battery.
(16) Start engine and check for leaks.
FUEL TANK
DESCRIPTION
The fuel tank is constructed of a plastic material.
Its main functions are for fuel storage and for place-
ment of the fuel pump module, and certain ORVR
components.
OPERATION
All models pass a full 360 degree rollover test
without fuel leakage. To accomplish this, fuel and
vapor flow controls are required for all fuel tank con-
nections.
A check (control) valve is mounted into the top sec-
tion of the 2±piece fuel pump module. Refer to Fuel
Tank Check Valve for additional information.
An evaporation control system is connected to the
fuel tank to reduce emissions of fuel vapors into the
atmosphere. When fuel evaporates from the fuel
tank, vapors pass through vent hoses or tubes to a
charcoal canister where they are temporarily held.
When the engine is running, the vapors are drawn
into the intake manifold. Certain models are also
equipped with a self-diagnosing system using a Leak
Detection Pump (LDP) and/or an ORVR system.
Refer to Emission Control System for additional
information.
14 - 24 FUEL DELIVERYKJ
FUEL RAIL (Continued)

3.7L
The Throttle Position Sensor (TPS) is mounted to
the throttle body (Fig. 32), or (Fig. 33).
(1) Disconnect TPS electrical connector.
(2) Remove 2 TPS mounting screws.
(3) Remove TPS.
INSTALLATION
2.4L
The Throttle Position Sensor (TPS) is mounted to
the rear of the throttle body.
The throttle shaft end of the throttle body slides
into a socket in the TPS (Fig. 33). The TPS must be
installed so that it can be rotated a few degrees. (If
sensor will not rotate, install sensor with throttle
shaft on other side of socket tangs). The TPS will be
under slight tension when rotated.
(1) Install TPS and retaining screws.
(2) Tighten screws to 7 N´m (60 in. lbs.) torque.
(3) Connect TPS electrical connector to TPS.(4) Manually operate throttle (by hand) to check
for any TPS binding before starting engine.
(5) Install air cleaner tube to throttle body.
3.7L
The Throttle Position Sensor (TPS) is mounted to
the throttle body (Fig. 32).
The throttle shaft end of the throttle body slides
into a socket in the TPS (Fig. 33). The TPS must be
installed so that it can be rotated a few degrees. (If
sensor will not rotate, install sensor with throttle
shaft on other side of socket tangs). The TPS will be
under slight tension when rotated.
(1) Install TPS and retaining screws.
(2) Tighten screws to 7 N´m (60 in. lbs.) torque.
(3) Connect TPS electrical connector to TPS.
(4) Manually operate throttle (by hand) to check
for any TPS binding before starting engine.
(5) Install air cleaner tube to throttle body.
Fig. 32 TPS/IAC MOTOR - 3.7L
1 - THROTTLE POSITION SENSOR (TPS)
2 - MOUNTING SCREWS
3 - IDLE AIR CONTROL MOTOR (IAC)
4 - MOUNTING SCREWS
Fig. 33 TPS INSTALLATION - 3.7
1 - THROTTLE BODY
2 - TPS
3 - THROTTLE BODY SHAFT
4 - SOCKET LOCATING TANGS
14 - 48 FUEL INJECTIONKJ
THROTTLE POSITION SENSOR (Continued)

NOTE: Power steering pumps have different pres-
sure rates and are not interchangeable with other
pumps.
STANDARD PROCEDURE - POWER STEERING
PUMP - INITIAL OPERATION
WARNING: THE FLUID LEVEL SHOULD BE
CHECKED WITH ENGINE OFF TO PREVENT INJURY
FROM MOVING COMPONENTS.
CAUTION: Use MOPAR Power Steering Fluid or
equivalent. Do not use automatic transmission fluid
and do not overfill.
Wipe filler cap clean, then check the fluid level.
The dipstick should indicateCOLDwhen the fluid is
at normal ambient temperature.
(1) Fill the pump fluid reservoir to the proper level
and let the fluid settle for at least two minutes.
(2) Raise the front wheels off the ground.
(3) Slowly turn the steering wheel right and left,
lightly contacting the wheel stops at least 20 times.
(4) Check the fluid level add if necessary.
(5) Lower the vehicle, start the engine and turn
the steering wheel slowly from lock to lock.
(6) Stop the engine and check the fluid level and
refill as required.
CAUTION: Do not run a vehicle with foamy fluid for
an extended period. This may cause pump damage.
(7) If the fluid is extremely foamy or milky look-
ing, allow the vehicle to stand a few minutes and
repeat the procedure.
(8) Add fluid if necessary. Repeat the above proce-
dure until the fluid level remains constant after run-
ning the engine.
REMOVAL
REMOVAL - 3.7L
(1) Siphon out as much power steering fluid as
possible.
(2) Remove the radiator cross member (Refer to 23
- BODY/EXTERIOR/RADIATOR CROSSMEMBER -
REMOVAL).
(3) Remove the engine cooling fan (Refer to 7 -
COOLING/ENGINE/RADIATOR FAN - REMOVAL).
(4) Remove the fan shroud
(5) Remove the serpentine drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(6) Remove the power steering high pressure hose
at the pump.
(7) Remove the return hose at the pump.
(8) Remove the three bolts securing the pump to
the bracket thru the holes in the pulley. (Fig. 3)
(9) Remove the pump from the vehicle.
REMOVAL - 2.4L
CAUTION: On vehicles equipped with the 2.4L, Do
not reuse the old power steering pump pulley it is
not intended for reuse. A new pulley must be
installed if removed.
(1) Siphon out as much power steering fluid as
possible.
(2) Remove the serpentine drive belt.
(3) Remove the power steering high pressure hose
at the pump using care not to remove the flow con-
trol valve.
(4) Remove the return hose at the pump.
Fig. 2 FLUID RESERVOIR - 2.4L
Fig. 3 POWER STEERING PUMP - 3.7L
1 - MOUNTING BOLTS
2 - RESERVOIR
3 - STEEL PULLEY
19 - 18 PUMPKJ
PUMP (Continued)