cli JEEP GRAND CHEROKEE 2002 WJ / 2.G Workshop Manual

ING & AIR CONDITIONING/PLUMBING/RE-
CEIVER / DRIER - INSTALLATION).
INSTALLATION - 2.7L TURBO DIESEL
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) The liquid line is serviced as an integral part of
the receiver/drier bottle assembly(Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING/RE-
CEIVER / DRIER - INSTALLATION).
SUCTION LINE
REMOVAL
REMOVAL
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)
(1) Disconnect and isolate the battery negative
cable.
(2) Recover the refrigerant from the refrigerant
system. (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT RECOVERY)
(3) Remove the retainer nut from the evaporator
connection (Fig. 8) or (Fig. 9).(4) Slide the suction line off the stud and liquid
line. Install plugs in, or tape over all the opened
refrigerant line fittings. Remove from clip.
(5) Remove the bolt that secures the suction line
fitting to compressor. Install plugs in, or tape over all
of the opened refrigerant line fittings.
(6) Remove the suction line assembly from the
vehicle.
Fig. 8 SUCTION LINE - I-6
1 - SUCTION LINE
2 - RECEIVER DRIER- LIQUID LINE
3 - H-BLOCK
Fig. 9 V-8 Suction Line
1 - SUCTION LINE TO H-BLOCK
2 - A/C COMPRESSOR
3 - SUCTION LINE TO COMPRESSOR
4 - RECEIVER DRIER ASSEMBLY
5 - H-BLOCK
WJPLUMBING 24 - 67
LIQUID LINE (Continued)

REMOVAL - 2.7L TURBO DIESEL
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)
(1) Disconnect the negative battery cable.
(2) Recover the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT
RECOVERY)
(3) Remove the refrigerant line retaining fastener
from the H-Valve Block (Fig. 10). Remove the line
and gasket from the H-Valve block and cap or tape
over both ends.
(4) Remove the refrigerant line support bracket
bolt from the cylinder head cap.
(5) Remove the refrigerant line retaining fastener
from the compressor inlet fitting. Remove the line
and cap the compressor outlet tube to prevent con-
tamination of the system.
(6) Unclip and remove the suction line from the
vehicle.
INSTALLATION
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) Remove the tape or plugs from the suction line
block fitting and the manifold on the compressor.
Install the suction line block fitting to the manifold
on the compressor. Tighten the mounting bolt to 25.4
N´m (225 in. lbs.).
(2) Remove the tape or plugs from the refrigerant
line fittings on the evaporator outlet and the suction
line. Slide the suction line copnnection block over the
liquid line and evaporator stud. Tighten the retaining
nut to 28 N´m (250 in. lbs.).
(3) Connect the battery negative cable.
(4) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(5) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
Fig. 10 Suction-Discharge Lines- RHD (LHD-typical)
1 - SUCTION LINE
2 - H-BLOCK
3 - RECEIVER DRIER
4 - DISCHARGE LINE & SERVICE PORT
5 - A/C COMPRESSOR
6 - DISCHARGE LINE & CONDENSOR CONNECTION
24 - 68 PLUMBINGWJ
SUCTION LINE (Continued)

REFRIGERANT
DESCRIPTION
The refrigerant used in this air conditioning sys-
tem is a HydroFluoroCarbon (HFC), type R-134a.
Unlike R-12, which is a ChloroFluoroCarbon (CFC),
R-134a refrigerant does not contain ozone-depleting
chlorine. R-134a refrigerant is a non-toxic, non-flam-
mable, clear, and colorless liquefied gas.
Even though R-134a does not contain chlorine, it
must be reclaimed and recycled just like CFC-type
refrigerants. This is because R-134a is a greenhouse
gas and can contribute to global warming.
OPERATION
R-134a refrigerant is not compatible with R-12
refrigerant in an air conditioning system. Even a
small amount of R-12 added to an R-134a refrigerant
system will cause compressor failure, refrigerant oil
sludge or poor air conditioning system performance.
In addition, the PolyAlkylene Glycol (PAG) synthetic
refrigerant oils used in an R-134a refrigerant system
are not compatible with the mineral-based refriger-
ant oils used in an R-12 refrigerant system.
R-134a refrigerant system service ports, service
tool couplers and refrigerant dispensing bottles have
all been designed with unique fittings to ensure that
an R-134a system is not accidentally contaminated
with the wrong refrigerant (R-12). There are also
labels posted in the engine compartment of the vehi-
cle and on the compressor identifying to service tech-
nicians that the air conditioning system is equipped
with R-134a.
REFRIGERANT OIL
DESCRIPTION
The refrigerant oil used in R-134a refrigerant sys-
tems is a synthetic-based, PolyAlkylene Glycol (PAG),
wax-free lubricant. Mineral-based R-12 refrigerant
oils are not compatible with PAG oils, and should
never be introduced to an R-134a refrigerant system.
There are different PAG oils available, and each
contains a different additive package. The 10PA17
compressor used in this vehicle is designed to use an
ND8 PAG refrigerant oil. Use only refrigerant oil of
this same type to service the refrigerant system.
OPERATION
After performing any refrigerant recovery or recy-
cling operation, always replenish the refrigerant sys-
tem with the same amount of the recommended
refrigerant oil as was removed. Too little refrigerant
oil can cause compressor damage, and too much can
reduce air conditioning system performance.PAG refrigerant oil is much more hygroscopic than
mineral oil, and will absorb any moisture it comes
into contact with, even moisture in the air. The PAG
oil container should always be kept tightly capped
until it is ready to be used. After use, recap the oil
container immediately to prevent moisture contami-
nation.
STANDARD PROCEDURE - REFRIGERANT OIL
LEVEL
When an air conditioning system is assembled at
the factory, all components except the compressor are
refrigerant oil free. After the refrigerant system has
been charged and operated, the refrigerant oil in the
compressor is dispersed throughout the refrigerant
system. The accumulator, evaporator, condenser, and
compressor will each retain a significant amount of
the needed refrigerant oil.
It is important to have the correct amount of oil in
the refrigerant system. This ensures proper lubrica-
tion of the compressor. Too little oil will result in
damage to the compressor. Too much oil will reduce
the cooling capacity of the air conditioning system.
It will not be necessary to check the oil level in the
compressor or to add oil, unless there has been an oil
loss. An oil loss may occur due to a rupture or leak
from a refrigerant line, a connector fitting, a compo-
nent, or a component seal. If a leak occurs, add 30
milliliters (1 fluid ounce) of refrigerant oil to the
refrigerant system after the repair has been made.
Refrigerant oil loss will be evident at the leak point
by the presence of a wet, shiny surface around the
leak.
Refrigerant oil must be added when a accumulator,
evaporator coil, or condenser are replaced. See the
Refrigerant Oil Capacities chart. When a compressor
is replaced, the refrigerant oil must be drained from
the old compressor and measured. Drain all of the
refrigerant oil from the new compressor, then fill the
new compressor with the same amount of refrigerant
oil that was drained out of the old compressor.
Refrigerant Oil Capacities
Component ml fl oz
A/C System 130 4.40
Receiver Drier 70 2.37
Condenser 10 0.34
Evaporator 50 1.69
Compressordrain and measure
the oil from the old
compressor - see
text.
WJPLUMBING 24 - 75

DESCRIPTION - STATE DISPLAY TEST MODE
The switch inputs to the Powertrain Control Mod-
ule (PCM) have two recognized states; HIGH and
LOW. For this reason, the PCM cannot recognize the
difference between a selected switch position versus
an open circuit, a short circuit, or a defective switch.
If the State Display screen shows the change from
HIGH to LOW or LOW to HIGH, assume the entire
switch circuit to the PCM functions properly. Connect
the DRB scan tool to the data link connector and
access the state display screen. Then access either
State Display Inputs and Outputs or State Display
Sensors.
DESCRIPTION - CIRCUIT ACTUATION TEST
MODE
The Circuit Actuation Test Mode checks for proper
operation of output circuits or devices the Powertrain
Control Module (PCM) may not internally recognize.
The PCM attempts to activate these outputs and
allow an observer to verify proper operation. Most of
the tests provide an audible or visual indication of
device operation (click of relay contacts, fuel spray,
etc.). Except for intermittent conditions, if a device
functions properly during testing, assume the device,
its associated wiring, and driver circuit work cor-
rectly. Connect the DRB scan tool to the data link
connector and access the Actuators screen.
DESCRIPTION - DIAGNOSTIC TROUBLE CODES
A Diagnostic Trouble Code (DTC) indicates the
PCM has recognized an abnormal condition in the
system.Remember that DTC's are the results of a sys-
tem or circuit failure, but do not directly iden-
tify the failed component or components.
NOTE: For a list of DTC's, refer to the charts in this
section.
BULB CHECK
Each time the ignition key is turned to the ON
position, the malfunction indicator (check engine)
lamp on the instrument panel should illuminate for
approximately 2 seconds then go out. This is done for
a bulb check.
OBTAINING DTC'S USING DRB SCAN TOOL
(1) Connect the DRB scan tool to the data link
(diagnostic) connector. This connector is located in
the passenger compartment; at the lower edge of
instrument panel; near the steering column.
(2) Turn the ignition switch on and access the
ªRead Faultº screen.
(3) Record all the DTC's and ªfreeze frameº infor-
mation shown on the DRB scan tool.
(4) To erase DTC's, use the ªErase Trouble Codeº
data screen on the DRB scan tool.Do not erase any
DTC's until problems have been investigated
and repairs have been performed.
(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
P0030 (M) 1/1 O2 Sensor Heater Circuit
MalfunctionProblem detected in oxygen sensor heater relay circuit.
P0031 (M) 1/1 O2 Sensor Heater Circuit Low Problem detected in oxygen sensor heater relay circuit.
P0032 (M) 1/1 O2 Sensor Heater Circuit High Problem detected in oxygen sensor heater relay circuit.
P0036 (M) 1/2 O2 Sensor Heater Circuit
MalfunctionProblem detected in oxygen sensor heater relay circuit.
P0037 (M) 1/2 O2 Sensor Heater Circuit Low Problem detected in oxygen sensor heater relay circuit.
P0038 (M) 1/2 O2 Sensor Heater Circuit High Problem detected in oxygen sensor heater relay circuit.
P0043 (M) 1/3 O2 Sensor Heater Circuit Low Problem detected in oxygen sensor heater relay circuit.
P0044 (M) 1/3 O2 Sensor Heater Circuit High Problem detected in oxygen sensor heater relay circuit.
P0051 (M) 2/1 O2 Sensor Heater Circuit Low Problem detected in oxygen sensor heater relay circuit.
P0052 (M) 2/1 O2 Sensor Heater Circuit High Problem detected in oxygen sensor heater relay circuit.
25 - 2 EMISSIONS CONTROLWJ
EMISSIONS CONTROL (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
P1687 No MIC BUS Message (No Cluster
BUS Message)No CCD/J1850 messages received from the Mechanical
Instrument Cluster (MIC) module.
P1688 (M) Internal Fuel Injection Pump
Controller FailureInternal problem within the fuel injection pump. Low
power, engine derated, or engine stops.
P1689 (M) No Communication Between ECM
and Injection Pump ModuleData link circuit failure between ECM and fuel injection
pump. Low power, engine derated, or engine stops.
P1690 (M) Fuel Injection Pump CKP Sensor
Does Not Agree With ECM CKP
SensorProblem in fuel sync signal. Possible injection pump
timing problem. Low power, engine derated, or engine
stops.
P1691 Fuel Injection Pump Controller
Calibration ErrorInternal fuel injection pump failure. Low power, engine
derated, or engine stops.
P1692 DTC Set In ECM A9Companion DTC9was set in both the ECM and PCM.
P1693 (M) DTC Detected in Companion Module A fault has been generated in the companion engine
control module.
P1693 (M) DTC Detected in PCM/ECM or DTC
Detected in ECMA9Companion DTC9was set in both the ECM and PCM.
P1694 Fault In Companion Module No CCD/J1850 messages received from the powertrain
control module-Aisin transmission
P1694 (M) No BUS (CCD) Messages received
from ECMBus communication failure to PCM.
P1695 No CCD/J1850 Message From Body
Control ModuleNo CCD/J1850 messages received from the body control
module.
P1696 PCM Failure EEPROM Write Denied Unsuccessful attempt to write to an EEPROM location by
the control module.
P1697 PCM Failure SRI Mile Not Stored Unsuccessful attempt to update Service Reminder
Indicator (SRI or EMR) mileage in the control module
EEPROM.
P1698 No CCD/J1850 Message From TCM No CCD/J1850 messages received from the electronic
transmission control module (EATX) or the Aisin
transmission controller.
P1698 No CCD Messages received from
PCMBus communication failure to PCM. A9Companion DTC9
was set in both the ECM and PCM.
P1699 No Climate Control Bus Messages
P1719 Skip Shift Solenoid Circuit An open or shorted condition detected in the transmission
2-3 gear lock-out solenoid control circuit.
P1740 TCC or OD Sol Perf A rationality error has been detected in either the TCC
solenoid or overdrive solenoid systems.
P1740 (M) TCC OR O/D Solenoid Performance Problem detected in transmission convertor clutch and/or
overdrive circuits (diesel engine with 4-speed auto. trans.
only).
WJEMISSIONS CONTROL 25 - 15
EMISSIONS CONTROL (Continued)

tive system and seal the evaporative system so the
leak detection test can be run.
The primary components within the assembly are:
A three port solenoid that activates both of the func-
tions listed above; a pump which contains a switch,
two check valves and a spring/diaphragm, a canister
vent valve (CVV) seal which contains a spring loaded
vent seal valve.
Immediately after a cold start, between predeter-
mined temperature thresholds limits, the three port
solenoid is briefly energized. This initializes the
pump by drawing air into the pump cavity and also
closes the vent seal. During non test conditions the
vent seal is held open by the pump diaphragm
assembly which pushes it open at the full travel posi-
tion. The vent seal will remain closed while the
pump is cycling due to the reed switch triggering of
the three port solenoid that prevents the diaphragm
assembly from reaching full travel. After the brief
initialization period, the solenoid is de-energized
allowing atmospheric pressure to enter the pump
cavity, thus permitting the spring to drive the dia-
phragm which forces air out of the pump cavity and
into the vent system. When the solenoid is energized
and de energized, the cycle is repeated creating flow
in typical diaphragm pump fashion. The pump is con-
trolled in 2 modes:
Pump Mode:The pump is cycled at a fixed rate to
achieve a rapid pressure build in order to shorten the
overall test length.
Test Mode:The solenoid is energized with a fixed
duration pulse. Subsequent fixed pulses occur when
the diaphragm reaches the Switch closure point.
The spring in the pump is set so that the system
will achieve an equalized pressure of about 7.5º
water. The cycle rate of pump strokes is quite rapid
as the system begins to pump up to this pressure. As
the pressure increases, the cycle rate starts to drop
off. If there is no leak in the system, the pump would
eventually stop pumping at the equalized pressure. If
there is a leak, it will continue to pump at a rate rep-
resentative of the flow characteristic of the size of the
leak. From this information we can determine if the
leak is larger than the required detection limit (cur-
rently set at .040º orifice by CARB). If a leak is
revealed during the leak test portion of the test, the
test is terminated at the end of the test mode and no
further system checks will be performed.
After passing the leak detection phase of the test,
system pressure is maintained by turning on the
LDP's solenoid until the purge system is activated.
Purge activation in effect creates a leak. The cycle
rate is again interrogated and when it increases due
to the flow through the purge system, the leak check
portion of the diagnostic is complete.The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.
Evaporative system functionality will be verified by
using the stricter evap purge flow monitor. At an
appropriate warm idle the LDP will be energized to
seal the canister vent. The purge flow will be clocked
up from some small value in an attempt to see a
shift in the 02 control system. If fuel vapor, indicated
by a shift in the 02 control, is present the test is
passed. If not, it is assumed that the purge system is
not functioning in some respect. The LDP is again
turned off and the test is ended.
MISFIRE MONITOR
Excessive engine misfire results in increased cata-
lyst temperature and causes an increase in HC emis-
sions. Severe misfires could cause catalyst damage.
To prevent catalytic convertor damage, the PCM
monitors engine misfire.
The Powertrain Control Module (PCM) monitors
for misfire during most engine operating conditions
(positive torque) by looking at changes in the crank-
shaft speed. If a misfire occurs the speed of the
crankshaft will vary more than normal.
FUEL SYSTEM MONITOR
To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro-
gen and carbon monoxide. The catalyst works best
when the Air Fuel (A/F) ratio is at or near the opti-
mum of 14.7 to 1.
The PCM is programmed to maintain the optimum
air/fuel ratio of 14.7 to 1. This is done by making
short term corrections in the fuel injector pulse width
based on the O2S sensor output. The programmed
memory acts as a self calibration tool that the engine
controller uses to compensate for variations in engine
specifications, sensor tolerances and engine fatigue
over the life span of the engine. By monitoring the
actual fuel-air ratio with the O2S sensor (short term)
and multiplying that with the program long-term
(adaptive) memory and comparing that to the limit,
it can be determined whether it will pass an emis-
sions test. If a malfunction occurs such that the PCM
cannot maintain the optimum A/F ratio, then the
MIL will be illuminated.
CATALYST MONITOR
To comply with clean air regulations, vehicles are
equipped with catalytic converters. These converters
reduce the emission of hydrocarbons, oxides of nitro-
gen and carbon monoxide.
Normal vehicle miles or engine misfire can cause a
catalyst to decay. This can increase vehicle emissions
25 - 18 EMISSIONS CONTROLWJ
EMISSIONS CONTROL (Continued)

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)

²No engine stall during test.
NOTE: IF BATTERY VOLTAGE DROPS BELOW 10
VOLTS FOR MORE THAN 5 SECONDS DURING
ENGINE CRANKING, THE EVAP LEAK DETECTION
TEST WILL NOT RUN.
NOTE: THE FOLLOWING VALUES ARE APPROXI-
MATE AND VEHICLE SPECIFIC. USE THE VALUES
SEEN IN PRE TEST/MONITOR TEST SCREEN ON
THE DRB IIIT. SEE TSB 25-02-98 FOR MORE
DETAIL.
A DTC will not be set if a one-trip fault is set or if
the MIL is illuminated for any of the following:
²Purge Solenoid Electrical Fault
²All TPS Faults
²All Engine Controller Self Test Faults
²LDP Pressure Switch Fault
²All Cam and/or Crank Sensor Fault
²EGR Solenoid Electrical Fault
²All MAP Sensor Faults
²All Injector Faults
²Ambient/Battery Temperature Sensor Electrical
Faults²Baro Out of Range
²Vehicle Speed Faults
²All Coolant Sensor Faults
²LDP Solenoid Circuit
NOTE: IF BATTERY TEMPERATURE IS NOT WITHIN
RANGE, OR IF THE ENGINE COOLANT TEMPERA-
TURE IS NOT WITHIN A SPECIFIED RANGE OF THE
BATTERY TEMPERATURE, THE PCM WILL NOT
RUN TESTS FOR DTC P1494, P1486, P0442, P0455
AND P0441. THESE TEMPERATURE CALIBRATIONS
MAY BE DIFFERENT BETWEEN MODELS.
SECTION 1 - P1495 Leak Detection Pump
Solenoid Circuit-When the ignition key is turned
to9ON9, the LDP diaphragm should be in the down
position and the LDP reed switch should be closed. If
the EVAP system has residual pressure, the LDP dia-
phragm may be up. This could result in the LDP reed
switch being open when the key is turned to9ON9
and a P1494 fault could be set because the PCM is
expecting the reed switch to be closed.
After the key is turned9ON9, the PCM immedi-
ately tests the LDP solenoid circuit for electrical
faults. If a fault is detected, DTC P1495 will set, the
Fig. 15 DIAPHRAGM DOWNWARD MOVEMENT
1 - Diaphragm
2 - Inlet Check Valve (Closed)
3 - Vent Valve (Closed)
4 - From Air Filter
5 - To Canister
6 - Outlet Check Valve (Open)
7 - Engine Vacuum (Closed)EVAP LDP TEST SEQUENCE
1 - IGNITION SWITCH
2 - LDP DIAPHRAM
3 - LDP SWITCH
4 - LDP SOLENOID
5 - SECTION 1
6 - SECTION 2
7 - SECTION 3
8 - SECTION 4
9 - SECTION 5
10 - 3 TEST CYCLES TO TEST FOR BLOCKAGE
11- RAPID PUMP CYCLING FOR 70 CYCLES
WJEVAPORATIVE EMISSIONS 25 - 33
LEAK DETECTION PUMP (Continued)

MIL will illuminate, and the remaining EVAP Leak
Detection Test is canceled.
SECTION 2 - P1494 Leak Detection Pump
Switch or Mechanical Fault-If DTC P1495 is not
set, the PCM will check for DTC P1494. If the LDP
reed switch was closed when the key was turned to
9ON9, the PCM energizes the LDP solenoid for up to
8 seconds and monitors the LDP switch. As the LDP
diaphragm is pulled up by engine vacuum, the LDP
reed switch should change from closed to open. If it
does not, the PCM sets a temporary fault (P1494) in
memory, and waits until the next time the Enabling
Conditions are met to run the test again. If this is
again detected, P1494 is stored and the MIL is illu-
minated. If the problem is not detected during the
next enabling cycle, the temporary fault will be
cleared.
However, if the PCM detects the reed switch open
when the key is turned to9ON9, the PCM must deter-
mine if this condition is due to residual pressure in
the EVAP system, or an actual fault. The PCM stores
information in memory on EVAP system purging
from previous engine run or drive cycles.
If little or no purging took place, residual pressure
could be holding the LDP diaphragm up, causing the
LDP switch to be open. Since this is not a malfunc-
tion, the PCM cancels the EVAP Leak Detection Test
without setting the temporary fault.
If there was sufficient purging during the previous
cycle to eliminate EVAP system pressure, the PCM
judges that this is a malfunction and sets a tempo-
rary fault in memory. The next time that the
Enabling Conditions are met, the test will run again.
If the fault is again detected, the MIL will illuminate
and DTC P1494 will be stored. If the fault is not
detected, the temporary fault will be cleared.
SECTION 3 - P1486 EVAP Leak Monitor
Pinched Hose Found-If no fault has been detected
so far, the PCM begins testing for possible blockage
in the EVAP system between the LDP and the fuel
tank. This is done by monitoring the time required
for the LDP to pump air into the EVAP system dur-
ing two to three pump cycles. If no blockage is
present, the LDP diaphragm is able to quickly pump
air out of the LDP each time the PCM turns off the
LDP solenoid. If a blockage is present, the PCM
detects that the LDP takes longer to complete each
pump cycle. If the pump cycles take longer than
expected (approximately 6 to 10 seconds) the PCM
will suspect a blockage. On the next drive when
Enabling Conditions are met, the test will run again.
If blockage is again detected, P1486 is stored, and
the MIL is illuminated.
SECTION4-NoDTCCanBeSetDuring This
Time-After the LDP blockage tests are completed,
the PCM then tests for EVAP system leakage. First,the PCM commands the LDP to rapidly pump for 20
to 50 seconds (depending on fuel level) to build pres-
sure in the EVAP system. This evaluates the system
J18-24-0 to see if it can be sufficiently pressurized.
This evaluation (rapid pump cycling) may occur sev-
eral times prior to leak checking. The LDP reed
switch does not close and open during rapid pumping
because the diaphragm does not travel through its
full range during this part of the test.
SECTION 5 - P0456, P0442, P0455 EVAP Leak
Monitor and Leak Detected-Next, the PCM per-
forms one or more test cycles by monitoring the time
required for the LDP reed switch to close (diaphragm
to drop) after the LDP solenoid is turned off.
If the switch does not close, or closes after a long
delay, it means that the system does not have any
significant leakage and the EVAP Leak Detection
Test is complete.
However, if the LDP reed switch closes quickly,
there may be a leak or the fuel level may be low
enough that the LDP must pump more to finish pres-
surizing the EVAP system. In this case, the PCM will
rapidly pump the LDP again to build pressure in the
EVAP system, and follow that by monitoring the time
needed for several LDP test cycles. This process of
rapid pumping followed by several LDP test cycles
may repeat several times before the PCM judges that
a leak is present.
When leaks are present, the LDP test cycle time
will be inversely proportional to the size of the leak.
The larger the leak, the shorter the test cycle time.
The smaller the leak, the longer the test cycle time.
DTC's may be set when a leak as small as 0.5 mm
(0.0209) diameter is present.
If the system detects a leak, a temporary fault will
be stored in PCM memory. The time it takes to detect
a .020, .040, or Large leak is based on calibrations
that vary from model to model. The important point
to remember is if a leak is again detected on the next
EVAP Leak Detection Test, the MIL will illuminate
and a DTC will be stored based on the size of leak
detected. If no leak is detected during the next test,
the temporary fault will be cleared.
DIAGNOSTIC TIPS During diagnosis, you can
compare the LDP solenoid activity with the monitor
sequence in Figure 6. If the PCM detects a problem
that could set a DTC, the testing is halted and LDP
solenoid activity will stop. As each section of the test
begins, it indicates that the previous section passed
successfully. By watching to see which tests complete,
you can see if any conditions are present that the
PCM considers abnormal.
For example, if the LDP solenoid is energized for
the test cycles to test for blockage (P1486), it means
that the LDP has already passed its test for P1494.
Then, if the PCM detects a possible blockage, it will
25 - 34 EVAPORATIVE EMISSIONSWJ
LEAK DETECTION PUMP (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)