2003 JEEP GRAND CHEROKEE low oil pressure

INSTALLATION
WARNING: REVIEW THE WARNINGS AND CAU-
TIONS IN THE FRONT OF THIS SECTION BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - WARNING) (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - CAUTION)
Any kinks or sharp bends in the refrigerant plumb-
ing will reduce the capacity of the entire air condi-
tioning system. Kinks and sharp bends reduce the
flow of refrigerant in the system. A good rule for the
flexible hose refrigerant lines is to keep the radius of
all bends at least ten times the diameter of the hose.
In addition, the flexible hose refrigerant lines should
be routed so they are at least 80 millimeters (3
inches) from the exhaust manifold.High pressures are produced in the refrigerant sys-
tem when the air conditioning compressor is operat-
ing. Extreme care must be exercised to make sure
that each of the refrigerant system connections is
pressure-tight and leak free. It is a good practice to
inspect all flexible hose refrigerant lines at least once
a year to make sure they are in good condition and
properly routed.
(1) Install the evaporator coil in the bottom half of
the HVAC housing. Be certain that the evaporator
foam insulator wrap is reinstalled.
(2) Reassemble the HVAC housing and install in
the vehicle. (Refer to 24 - HEATING & AIR CONDI-
TIONING/DISTRIBUTION/HVAC HOUSING -
ASSEMBLY) (Refer to 24 - HEATING & AIR CON-
DITIONING/DISTRIBUTION/HVAC HOUSING -
INSTALLATION)
NOTE: If the evaporator is replaced, add 60 millili-
ters (2 fluid ounces) of refrigerant oil to the refrig-
erant system.
Fig. 11 HVAC HOUSING- CASE SEPARATED
1 - ELECTRICIAL CONNECTORS
2 - VACUUM ACTUATOR
3 - RECIRCULATION DOOR
4 - THERMAL EXPANSION VALVE
5 - BLOWER MOTOR RESISTOR/CONTROLLER
6 - BLOWER WHEEL
7 - EVAPORATOR AND TUBES
8 - FIN SENSOR PROBE9 - BLEND DOOR
10 - PIVOT SHAFT (MOTOR REMOVED)
11 - PANEL/OUTLET DOOR
12 - LOWER HOUSING
13 - VACUUM ACTUATORS
14 - UPPER HOUSING
15 - VACUUM HARNESS
24 - 70 PLUMBINGWJ
A/C EVAPORATOR (Continued)

(M)Malfunction Indicator Lamp (MIL) illuminated during engine operation if this DTC was recorded
(depending if required by CARB and/or EPA). MIL is displayed as an engine icon on instrument panel.
(G)Generator lamp illuminated
Generic Scan
Tool P-CodeDRB Scan Tool Display Brief Description of DTC
P0406 EGR Position Sensor Volts Too High EGR position sensor input above the acceptable voltage
range.
P0412 Secondary Air Solenoid Circuit An open or shorted condition detected in the secondary
air (air switching/aspirator) solenoid control circuit.
P0420 (M) 1/1 Catalytic Converter Efficiency Catalyst 1/1 efficiency below required level.
P0432 (M) 1/2 Catalytic Converter Efficiency Catalyst 2/1 efficiency below required level.
P0441 (M) Evap Purge Flow Monitor Insufficient or excessive vapor flow detected during
evaporative emission system operation.
P0442 (M) Evap Leak Monitor Medium Leak
DetectedA small leak has been detected in the evaporative
system.
P0443 (M) Evap Purge Solenoid Circuit An open or shorted condition detected in the EVAP purge
solenoid control circuit.
P0455 (M) Evap Leak Monitor Large Leak
DetectedA large leak has been detected in the evaporative system.
P0456 (M) Evap Leak Monitor Small Leak
DetectedLeak has been detected in the evaporative system.
P0460 Fuel Level Unit No Change Over
MilesDuring low fuel
P0460 Fuel Level Unit No Change Over
MilesFuel level sending unit voltage does not change for more
than 40 miles.
PO061 Fuel Level Unit No Change Over
Time
P0462 Fuel Level Sending Unit Volts Too
LowFuel level sensor input below acceptable voltage.
P0462 (M) Fuel Level Sending Unit Volts Too
LowOpen circuit between PCM and fuel gauge sending unit.
P0463 Fuel Level Sending Unit Volts Too
HighFuel level sensor input above acceptable voltage.
P0463 (M) Fuel Level Sending Unit Volts Too
HighCircuit shorted to voltage between PCM and fuel gauge
sending unit.
P0500 (M) No Vehicle Speed Sensor Signal No vehicle speed sensor signal detected during road load
conditions.
P0500 (M) No Vehicle Speed Sensor Signal A vehicle speed signal was not detected.
P0505 (M) Idle Air Control Motor Circuits
P0508 (M) IAC Motor Sense Circuit Low
P0509 (M) IAC Motor Sense Circuit High
P0521 Oil Pressure Switch Rationality
P0522 Oil Pressure Voltage Too Low Oil pressure sending unit (sensor) voltage input below the
minimum acceptable voltage.
P0523 Oil Pressure Voltage Too High Oil pressure sending unit (sensor) voltage input above the
maximum acceptable voltage.
P0524 Oil Pressure Too Low Engine oil pressure is low. Engine power derated.
25 - 8 EMISSIONS CONTROLWJ
EMISSIONS CONTROL (Continued)

an associated limp in will take two trips to illumi-
nate the MIL.
Refer to the Diagnostic Trouble Codes Description
Charts in this section and the appropriate Power-
train Diagnostic Procedure Manual for diagnostic
procedures.
DESCRIPTION - NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems and conditions that could have malfunctions
causing driveability problems. The PCM might not
store diagnostic trouble codes for these conditions.
However, problems with these systems may cause the
PCM to store diagnostic trouble codes for other sys-
tems or components. For example, a fuel pressure
problem will not register a fault directly, but could
cause a rich/lean condition or misfire. This could
cause the PCM to store an oxygen sensor or misfire
diagnostic trouble code
FUEL PRESSURE
The fuel pressure regulator controls fuel system
pressure. The PCM cannot detect a clogged fuel
pump inlet filter, clogged in-line fuel filter, or a
pinched fuel supply or return line. However, these
could result in a rich or lean condition causing the
PCM to store an oxygen sensor or fuel system diag-
nostic trouble code.
SECONDARY IGNITION CIRCUIT
The PCM cannot detect an inoperative ignition coil,
fouled or worn spark plugs, ignition cross firing, or
open spark plug cables.
CYLINDER COMPRESSION
The PCM cannot detect uneven, low, or high engine
cylinder compression.
EXHAUST SYSTEM
The PCM cannot detect a plugged, restricted or
leaking exhaust system, although it may set a fuel
system fault.
FUEL INJECTOR MECHANICAL MALFUNCTIONS
The PCM cannot determine if a fuel injector is
clogged, the needle is sticking or if the wrong injectoris installed. However, these could result in a rich or
lean condition causing the PCM to store a diagnostic
trouble code for either misfire, an oxygen sensor, or
the fuel system.
EXCESSIVE OIL CONSUMPTION
Although the PCM monitors engine exhaust oxygen
content when the system is in closed loop, it cannot
determine excessive oil consumption.
THROTTLE BODY AIRFLOW
The PCM cannot detect a clogged or restricted air
cleaner inlet or filter element.
VACUUM ASSIST
The PCM cannot detect leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices. However, these could cause the PCM
to store a MAP sensor diagnostic trouble code and
cause a high idle condition.
PCM SYSTEM GROUND
The PCM cannot determine a poor system ground.
However, one or more diagnostic trouble codes may
be generated as a result of this condition. The mod-
ule should be mounted to the body at all times, also
during diagnostic.
PCM CONNECTOR ENGAGEMENT
The PCM may not be able to determine spread or
damaged connector pins. However, it might store
diagnostic trouble codes as a result of spread connec-
tor pins.
DESCRIPTION - HIGH AND LOW LIMITS
The PCM compares input signal voltages from each
input device with established high and low limits for
the device. If the input voltage is not within limits
and other criteria are met, the PCM stores a diagnos-
tic trouble code in memory. Other diagnostic trouble
code criteria might include engine RPM limits or
input voltages from other sensors or switches that
must be present before verifying a diagnostic trouble
code condition.
DESCRIPTION - LOAD VALUE
ENGINE IDLE/NEUTRAL 2500 RPM/NEUTRAL
All Engines 2% to 8% of Maximum Load 9% to 17% of Maximum Load
25 - 20 EMISSIONS CONTROLWJ
EMISSIONS CONTROL (Continued)

²a PCV valve mounted to the oil filler housing
(Fig. 3). The PCV valve is sealed to the oil filler
housing with an o-ring.
²the air cleaner housing
²two interconnected breathers threaded into the
rear of each cylinder head (Fig. 4).
²tubes and hose to connect the system compo-
nents.
OPERATION
OPERATION - 4.0L CCV SYSTEM
The CCV system performs the same function as a
conventional PCV system, but does not use a vacuum
controlled PCV valve.
The fixed orifice fitting meters the amount of
crankcase vapors drawn out of the engine.
When the engine is operating, fresh air enters the
engine and mixes with crankcase vapors. Engine vac-uum draws the vapor/air mixture through the fixed
orifice and into the intake manifold. The vapors are
then consumed during engine combustion.
OPERATION - 4.7L PCV SYSTEM
The PCV system operates by engine intake mani-
fold vacuum. Filtered air is routed into the crankcase
through the air cleaner hose and crankcase breath-
ers. The metered air, along with crankcase vapors,
are drawn through the PCV valve and into a passage
in the intake manifold. The PCV system manages
crankcase pressure and meters blow-by gases to the
intake system, reducing engine sludge formation.
The PCV valve contains a spring loaded plunger.
This plunger meters the amount of crankcase vapors
routed into the combustion chamber based on intake
manifold vacuum.
TYPICALPCV valves are shown in (Fig. 5), (Fig.
6) and (Fig. 7).
When the engine is not operating, or during an
engine pop-back, the spring forces the plunger back
against the seat (Fig. 5). This will prevent vapors
from flowing through the valve.
Fig. 3 PCV Valve/Oil Filler Tube (Housing)Ð4.7L
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. 4 PCV System Hoses/TubesÐ4.7L Engine
1 - FRESH AIR FITTING
2 - CONNECTING TUBES/HOSES
3 - CRANKCASE BREATHERS (2)
4 - RUBBER HOSE
5 - AIR CLEANER RESONATOR
25 - 26 EVAPORATIVE EMISSIONSWJ
EVAPORATIVE EMISSIONS (Continued)

set a temporary fault without turning on the MIL
and continue the leak portion of the test. However,
the PCM will assume that the system is already
pressurized and skip the rapid pump cycles.
Always diagnose leaks, if possible, before discon-
necting connections. Disconnecting connections may
mask a leak condition.
Keep in mind that if the purge solenoid seat is
leaking, it could go undetected since the leak would
end up in the intake manifold. Disconnect the purge
solenoid at the manifold when leak checking. In addi-
tion, a pinched hose fault (P1486) could set if the
purge solenoid does not purge the fuel system prop-
erly (blocked seat). The purge solenoid must vent the
fuel system prior to the LDP system test. If the
purge solenoid cannot properly vent the system the
LDP cannot properly complete the test for P1486 and
this fault can set due to pressure being in the EVAP
system during the test sequence.
Multiple actuation's of the DRB IIItLeak Detec-
tion Pump (LDP) Monitor Test can hide a 0.020 leak
because of excess vapor generation. Additionally, any
source for additional vapor generation can hide a
small leak in the EVAP system. Excess vapor gener-
ation can delay the fall of the LDP diaphragm thus
hiding the small leak. An example of this condition
could be bringing a cold vehicle into a warm shop for
testing or high ambient temperatures.
Fully plugged and partially plugged underhood
vacuum lines have been known to set MIL condi-
tions. P1494 and P0456 can be set for this reason.
Always, thoroughly, check plumbing for pinches or
blockage before condemning components.
TEST EQUIPMENT The Evaporative Emission
Leak Detector (EELD) Miller Special Tool 8404 is
capable of visually detecting leaks in the evaporative
system and will take the place of the ultrasonic leak
detector 6917A. The EELD utilizes shop air and a
smoke generator to visually detect leaks down to
0.020 or smaller. The food grade oil used to make the
smoke includes an UV trace dye that will leave tell-
tale signs of the leak under a black light. This is
helpful when components have to be removed to
determine the exact leak location. For detailed test
instructions, follow the operators manual packaged
with the EELD.
NOTE: Be sure that the PCM has the latest software
update. Reprogram as indicated by any applicable
Technical Service Bulletin. After LDP repairs are
completed, verify the repair by running the DRB IIIT
Leak Detection Pump (LDP) Monitor Test as
described in Technical Service Bulletin 18-12-99.REMOVAL
The Leak Detection Pump (LDP) is located under
the left quarter panel behind the left/rear wheel (Fig.
16). It is attached to a two-piece support bracket
(Fig. 17). The LDP and LDP filter are replaced (ser-
viced) as one unit.
(1) Remove stone shield behind left/rear wheel
(Fig. 18). Drill out plastic rivets for removal.
(2) Remove 3 LDP mounting bolts (Fig. 19).
(3) Remove support bracket brace bolt (Fig. 17).
(4) Loosen, but do not remove 2 support bracket
nuts at frame rail (Fig. 19).
(5) To separate and lower front section of two-piece
support bracket, remove 3 attaching bolts on bottom
of support bracket (Fig. 17). While lowering support
bracket, disconnect LDP wiring clip (Fig. 20).
(6) Disconnect electrical connector at LDP (Fig.
20).
(7) Carefully remove vapor/vacuum lines at LDP
(Fig. 20).
(8) Remove LDP.
INSTALLATION
The LDP is located in the left quarter panel behind
the left/rear wheel. It is attached to a two-piece sup-
port bracket (Fig. 17). The LDP and LDP filter are
replaced (serviced) as one unit.
(1) Position LDP and carefully install vapor/vac-
uum lines to LDP and LDP filter.The vapor/vac-
uum lines and hoses must be firmly connected.
Fig. 16 LOCATION, LDP / EVAP CANISTER
1 - LEAK DETECTION PUMP
2 - EVAP CANISTER
WJEVAPORATIVE EMISSIONS 25 - 35
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)