2001 DODGE RAM ECU

(1) On gasoline engine models:
(a) Insert the two lower condenser locators into
the isolators in the holes of the lower crossmember.
(b) Tilt the condenser up towards the engine
compartment far enough to align the upper mount-
ing bracket holes with the holes in the upper radi-
ator crossmember.
(c) Install the two screws that secure the con-
denser upper mounting brackets to the outside of
the upper radiator crossmember. Tighten the
mounting screws to 10.5 N´m (95 in. lbs.).
(2) On diesel engine models:
(a) Install the driver side condenser mounting
brackets over the two studs on the charge air
cooler.
(b) Install the two screws that secure the brack-
ets on the passenger side end of the condenser to
the charge air cooler. Tighten the mounting screws
to 10.5 N´m (95 in. lbs.).
(c) Install the two nuts that secure the driver
side end of the condenser to the studs on the
charge air cooler. Tighten the mounting nuts to
10.5 N´m (95 in. lbs.).
(3) Remove the plugs or tape from the refrigerant
line fittings on the liquid line and the condenser out-
let. Connect the liquid line to the condenser outlet.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - STANDARD PROCEDURE - A/C LINE
COUPLERS)
(4) Install a new gasket and the discharge line
block fitting over the stud on the condenser inlet.
Tighten the mounting nut to 20 N´m (180 in. lbs.).
(5) Check that all of the condenser and radiator
air seals are in their proper locations.(6) Connect the battery negative cable.
(7) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(8) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
NOTE: If the condenser is replaced, add 30 millili-
ters (1 fluid ounce) of refrigerant oil to the refriger-
ant system. Use only refrigerant oil of the type
recommended for the compressor in the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/REFRIGERANT OIL - DESCRIPTION)
SUCTION AND DISCHARGE
LINE
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) Unplug the wire harness connector from the a/c
high pressure switch.
(4) Disconnect the suction line refrigerant line cou-
pler at the accumulator. (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - STANDARD
PROCEDURE - A/C LINE COUPLER) Install plugs
in, or tape over all of the opened refrigerant line fit-
tings.
(5) Remove the nut that secures the block fitting
to the stud on the condenser inlet and disconnect the
discharge line from the condenser. Install plugs in, or
tape over all of the opened refrigerant line fittings.
(6) On models with a gasoline engine, remove the
nut that secures the refrigerant line support bracket
to the stud on the compressor mounting bracket.
(7) Remove the bolt that secures the refrigerant
line manifold to the compressor (Fig. 8) or (Fig. 9).
Install plugs in, or tape over all of the opened refrig-
erant line fittings.
Fig. 7 CONDENSER REMOVE/INSTALL - DIESEL
ENGINE
1 - CHARGE AIR COOLER
2 - NUT
3 - CONDENSER
4 - SCREW
24 - 50 PLUMBINGBR/BE
A/C CONDENSER (Continued)

(3) Install the refrigerant line manifold to the com-
pressor. Tighten the mounting bolt to 22 N´m (200 in.
lbs.).
(4) On models with a gasoline engine, install the
nut that secures the refrigerant line support bracket
to the stud on the compressor mounting bracket.
Tighten the mounting nut to 22 N´m (200 in. lbs.).
(5) Plug in the wire harness connector to the a/c
high pressure switch.
(6) Connect the battery negative cable.
(7) Evacuate the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM EVACUATE)
(8) Charge the refrigerant system. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - REFRIGERANT SYS-
TEM CHARGE)
LIQUID LINE
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) Disconnect the liquid line refrigerant line cou-
plers at the condenser outlet and the evaporator
inlet. (Refer to 24 - HEATING & AIR CONDITION-
ING/PLUMBING - STANDARD PROCEDURE - A/C
LINE COUPLERS) Install plugs in, or tape over all
of the opened refrigerant line fittings.
(4) Disengage any clips that secure the liquid line
to the inner fender shield and the dash panel (Fig.
10).
(5) Remove the liquid line from the vehicle.
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)(Refer to
24 - HEATING & AIR CONDITIONING/PLUMBING -CAUTION - REFRIGERANT HOSES/LINES/TUBES
PRECAUTIONS)
(1) Install the liquid line into any clips on the
inner fender shield and the dash panel.
(2) Remove the tape or plugs from the refrigerant
line fittings on the liquid line, the condenser outlet,
and the evaporator inlet. Connect the liquid line to
the condenser and the evaporator. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - A/C LINE COUPLERS)
(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)
A/C EVAPORATOR
DESCRIPTION
The a/c evaporator is located in the HVAC housing,
under the instrument panel. The evaporator coil is
positioned in the HVAC housing so that all air that
enters the housing must pass over the fins of the
evaporator before it is distributed through the sys-
tem ducts and outlets. However, air passing over the
evaporator coil fins will only be conditioned when the
Fig. 10 LIQUID LINE REMOVE/INSTALL
1 - TO EVAPORATOR INLET
2 - CLIP
3 - EVAPORATOR INLET
4 - CONDENSER OUTLET
5 - CLIP
6 - TO CONDENSER OUTLET
7 - LIQUID LINE
8 - CLIPS
24 - 52 PLUMBINGBR/BE
SUCTION AND DISCHARGE LINE (Continued)

DIAGNOSIS AND TESTING - FIXED ORIFICE
TUBE
The fixed orifice tube can be checked for proper
operation using the following procedure. However,
the fixed orifice tube is only serviced as a part of the
liquid line unit. If the results of this test indicate
that the fixed orifice tube is obstructed or missing,
the entire liquid line unit must be replaced.
WARNING: THE LIQUID LINE BETWEEN THE CON-
DENSER OUTLET AND THE FIXED ORIFICE TUBE
CAN BECOME HOT ENOUGH TO BURN THE SKIN.
USE EXTREME CAUTION WHEN PERFORMING THE
FOLLOWING TEST.
(1) Confirm that the refrigerant system is properly
charged. (Refer to 24 - HEATING & AIR CONDI-
TIONING - DIAGNOSIS AND TESTING - A/C PER-
FORMANCE)
(2) Start the engine. Turn on the air conditioning
system and confirm that the compressor clutch is
engaged.
(3) Allow the air conditioning system to operate for
five minutes.
(4) Lightly and cautiously touch the liquid line
near the condenser outlet at the front of the engine
compartment. The liquid line should be hot to the
touch.
(5) Touch the liquid line near the evaporator inlet
at the rear of the engine compartment. The liquid
line should be cold to the touch.
(6) If there is a distinct temperature differential
between the two ends of the liquid line, the orifice
tube is in good condition. If there is little or no
detectable temperature differential between the two
ends of the liquid line, the orifice tube is obstructed
or missing and the liquid line must be replaced.
REMOVAL
The fixed orifice tube is located in the liquid line,
between the condenser and the evaporator coil. If the
fixed orifice tube is faulty or plugged, the liquid line
assembly must be replaced. (Refer to 24 - HEATING
& AIR CONDITIONING/PLUMBING/LIQUID LINE
- REMOVAL)
ACCUMULATOR
DESCRIPTION
The accumulator is mounted in the engine com-
partment between the a/c evaporator outlet tube and
the compressor inlet.
OPERATION
Refrigerant enters the accumulator canister as a
low pressure vapor through the inlet tube. Any liq-
uid, oil-laden refrigerant falls to the bottom of the
canister, which acts as a separator. A desiccant bag is
mounted inside the accumulator canister to absorb
any moisture which may have entered and become
trapped within the refrigerant system (Fig. 13).
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 a/c low pressure switch from the
accumulator. (Refer to 24 - HEATING & AIR CON-
DITIONING/CONTROLS/A/C LOW PRESSURE
SWITCH - REMOVAL)
(4) Loosen the screw that secures the accumulator
retaining band to the support bracket on the dash
panel (Fig. 20).
(5) Disconnect the suction line refrigerant line fit-
ting from the accumulator outlet. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
STANDARD PROCEDURE - A/C LINE COUPLERS)
Install plugs in, or tape over all of the opened refrig-
erant line fittings.
(6) Disconnect the accumulator inlet refrigerant
line fitting from the evaporator outlet. (Refer to 24 -
HEATING & AIR CONDITIONING/PLUMBING -
Fig. 12 FIXED ORIFICE TUBE - TYPICAL
1 - DIFFUSER SCREEN
2 - ªOº RINGS
3 - INLET FILTER SCREEN
4 - ORIFICE
24 - 54 PLUMBINGBR/BE
A/C ORIFICE TUBE (Continued)

more information on the engine cooling system, the
engine coolant and the heater hoses.
REMOVAL
(1) Remove the HVAC housing from the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
DISTRIBUTION/HVAC HOUSING - REMOVAL)
(2) Remove the screws and retainers that secure
the heater core to the HVAC housing.
(3) Lift the heater core straight up and out of the
heater-A/C housing (Fig. 14).
INSTALLATION
(1) Lower the heater core into the HVAC housing.
(2) Position the retainers over the heater core
tubes. Install and tighten the screws that secure the
heater core and retainers to the HVAC housing.
Tighten the screws to 2.2 N´m (20 in. lbs.).
(3) Reinstall the HVAC housing in the vehicle.
(Refer to 24 - HEATING & AIR CONDITIONING/
DISTRIBUTION/HVAC HOUSING - INSTALLA-
TION)
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 SD7H15
compressor used in this vehicle is designed to use an
SP-20 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
Fig. 14 HEATER CORE REMOVE/INSTALL
1 - HEATER CORE LINES
2 - HEATER CORE
24 - 56 PLUMBINGBR/BE
HEATER CORE (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
P1762 (M) Gov Press Sen Offset Volts Too Lo
or HighThe Governor Pressure Sensor input is greater than a
calibration limit or is less than a calibration limit for 3
consecutive park/neutral calibrations.
P1762 (M) Governor Press Sen Offset Volts Too
Low or HighSensor input greater or less than calibration for 3
consecutive Neutral/Park occurrences (4-speed auto.
trans. only).
P1763 Governor Pressure Sensor Volts Too
HiThe Governor Pressure Sensor input is above an
acceptable voltage level.
P1763 (M) Governor Pressure Sensor Volts Too
HIVoltage greater than 4.89 volts (4-speed auto. trans.
only).
P1764 (M) Governor Pressure Sensor Volts Too
LowThe Governor Pressure Sensor input is below an
acceptable voltage level.
P1764 (M) Governor Pressure Sensor Volts Too
LowVoltage less than .10 volts (4-speed auto. trans. only).
P1765 (M) Trans 12 Volt Supply Relay CTRL
CircuitAn open or shorted condition is detected in the
Transmission Relay control circuit. This relay supplies
power to the TCC
P1765 (M) Trans 12 Volt Supply Relay Ctrl
CircuitCurrent state of solenoid output port is different than
expected (4-speed auto. trans. only).
P1899 (M) P/N Switch Stuck in Park or in Gear Incorrect input state detected for the Park/Neutral switch.
P1899 (M) P/N Switch Stuck in Park or in Gear Incorrect input state detected for the Park/Neutral switch
(3 or 4-speed auto. trans. only).
DESCRIPTION - TASK MANAGER
The PCM is responsible for efficiently coordinating
the operation of all the emissions-related compo-
nents. The PCM is also responsible for determining if
the diagnostic systems are operating properly. The
software designed to carry out these responsibilities
is call the 'Task Manager'.
DESCRIPTION - MONITORED SYSTEMS
There are new electronic circuit monitors that
check fuel, emission, engine and ignition perfor-
mance. These monitors use information from various
sensor circuits to indicate the overall operation of the
fuel, engine, ignition and emission systems and thus
the emissions performance of the vehicle.
The fuel, engine, ignition and emission systems
monitors do not indicate a specific component prob-
lem. They do indicate that there is an implied prob-
lem within one of the systems and that a specific
problem must be diagnosed.
If any of these monitors detect a problem affecting
vehicle emissions, the Malfunction Indicator Lamp
(MIL) will be illuminated. These monitors generateDiagnostic Trouble Codes that can be displayed with
the MIL or a scan tool.
The following is a list of the system monitors:
²Misfire Monitor
²Fuel System Monitor
²Oxygen Sensor Monitor
²Oxygen Sensor Heater Monitor
²Catalyst Monitor
²Leak Detection Pump Monitor (if equipped)
All these system monitors require two consecutive
trips with the malfunction present to set a fault.
Refer to the appropriate Powertrain Diagnos-
tics Procedures manual for diagnostic proce-
dures.
The following is an operation and description of
each system monitor:
OXYGEN SENSOR (O2S) MONITOR
Effective control of exhaust emissions is achieved
by an oxygen feedback system. The most important
element of the feedback system is the O2S. The O2S
is located in the exhaust path. Once it reaches oper-
ating temperature 300É to 350ÉC (572É to 662ÉF), the
sensor generates a voltage that is inversely propor-
BR/BEEMISSIONS CONTROL 25 - 15
EMISSIONS CONTROL (Continued)

DTC Self Erasure
With one trip components or systems, the MIL is
illuminated upon test failure and DTCs are stored.
Two trip monitors are components requiring failure
in two consecutive trips for MIL illumination. Upon
failure of the first test, the Task Manager enters a
maturing code. If the component fails the test for a
second time the code matures and a DTC is set.
After three good trips the MIL is extinguished and
the Task Manager automatically switches the trip
counter to a warm-up cycle counter. DTCs are auto-
matically erased following 40 warm-up cycles if the
component does not fail again.
For misfire and fuel system monitors, the compo-
nent must pass the test under a Similar Conditions
Window in order to record a good trip. A Similar Con-
ditions Window is when engine RPM is within6375
RPM and load is within610% of when the fault
occurred.
NOTE: It is important to understand that a compo-
nent does not have to fail under a similar window of
operation to mature. It must pass the test under a
Similar Conditions Window when it failed to record
a Good Trip for DTC erasure for misfire and fuel
system monitors.
DTCs can be erased anytime with a DRB III. Eras-
ing the DTC with the DRB III erases all OBD II
information. The DRB III automatically displays a
warning that erasing the DTC will also erase all
OBD II monitor data. This includes all counter infor-
mation for warm-up cycles, trips and Freeze Frame.
Trip Indicator
TheTripis essential for running monitors and
extinguishing the MIL. In OBD II terms, a trip is a
set of vehicle operating conditions that must be met
for a specific monitor to run. All trips begin with a
key cycle.
Good Trip
The Good Trip counters are as follows:
²Specific Good Trip
²Fuel System Good Trip
²Misfire Good Trip
²Alternate Good Trip (appears as a Global Good
Trip on DRB III)
²Comprehensive Components
²Major Monitor
²Warm-Up Cycles
Specific Good Trip
The term Good Trip has different meanings
depending on the circumstances:
²If the MIL is OFF, a trip is defined as when the
Oxygen Sensor Monitor and the Catalyst Monitor
have been completed in the same drive cycle.²If the MIL is ON and a DTC was set by the Fuel
Monitor or Misfire Monitor (both continuous moni-
tors), the vehicle must be operated in the Similar
Condition Window for a specified amount of time.
²If the MIL is ON and a DTC was set by a Task
Manager commanded once-per-trip monitor (such as
the Oxygen Sensor Monitor, Catalyst Monitor, Purge
Flow Monitor, Leak Detection Pump Monitor, EGR
Monitor or Oxygen Sensor Heater Monitor), a good
trip is when the monitor is passed on the next start-
up.
²If the MIL is ON and any other emissions DTC
was set (not an OBD II monitor), a good trip occurs
when the Oxygen Sensor Monitor and Catalyst Mon-
itor have been completed, or two minutes of engine
run time if the Oxygen Sensor Monitor and Catalyst
Monitor have been stopped from running.
Fuel System Good Trip
To count a good trip (three required) and turn off
the MIL, the following conditions must occur:
²Engine in closed loop
²Operating in Similar Conditions Window
²Short Term multiplied by Long Term less than
threshold
²Less than threshold for a predetermined time
If all of the previous criteria are met, the PCM will
count a good trip (three required) and turn off the
MIL.
Misfire Good Trip
If the following conditions are met the PCM will
count one good trip (three required) in order to turn
off the MIL:
²Operating in Similar Condition Window
²1000 engine revolutions with no misfire
Warm-Up Cycles
Once the MIL has been extinguished by the Good
Trip Counter, the PCM automatically switches to a
Warm-Up Cycle Counter that can be viewed on the
DRB III. Warm-Up Cycles are used to erase DTCs
and Freeze Frames. Forty Warm-Up cycles must
occur in order for the PCM to self-erase a DTC and
Freeze Frame. A Warm-Up Cycle is defined as fol-
lows:
²Engine coolant temperature must start below
and rise above 160É F
²Engine coolant temperature must rise by 40É F
²No further faults occur
Freeze Frame Data Storage
Once a failure occurs, the Task Manager records
several engine operating conditions and stores it in a
Freeze Frame. The Freeze Frame is considered one
frame of information taken by an on-board data
recorder. When a fault occurs, the PCM stores the
input data from various sensors so that technicians
BR/BEEMISSIONS CONTROL 25 - 21
EMISSIONS CONTROL (Continued)

FUEL FILLER CAP
DESCRIPTION
The plastic fuel tank filler tube cap is threaded
onto the end of the fuel fill tube. Certain models are
equipped with a 1/4 turn cap.
OPERATION
The loss of any fuel or vapor out of fuel filler tube
is prevented by the use of a pressure-vacuum fuel fill
cap. Relief valves inside the cap will release fuel tank
pressure at predetermined pressures. Fuel tank vac-
uum will also be released at predetermined values.
This cap must be replaced by a similar unit if
replacement is necessary. This is in order for the sys-
tem to remain effective.
CAUTION: Remove fill cap before servicing any fuel
system component to relieve tank pressure. If
equipped with a Leak Detection Pump (LDP), the
cap must be tightened securely. If cap is left loose,
a Diagnostic Trouble Code (DTC) may be set.
REMOVAL/INSTALLATION
If replacement of the 1/4 turn fuel tank filler tube
cap is necessary, it must be replaced with an identi-
cal cap to be sure of correct system operation.CAUTION: Remove the fuel tank filler tube cap to
relieve fuel tank pressure. The cap must be
removed prior to disconnecting any fuel system
component or before draining the fuel tank.
LEAK DETECTION PUMP
DESCRIPTION
The Leak Detection Pump (LDP) is used only with
certain emission packages.
The LDP is a device used to detect a leak in the
evaporative system.
The pump contains a 3 port solenoid, a pump that
contains a switch, a spring loaded canister vent valve
seal, 2 check valves and a spring/diaphragm.
Immediately after a cold start, engine temperature
between 40ÉF and 86ÉF, the 3 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 test conditions, the vent seal is held
open by the pump diaphragm assembly which pushes
it open at the full travel position. The vent seal will
remain closed while the pump is cycling. This is due
to the operation of the 3 port solenoid which 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. This permits the spring to drive the
diaphragm which forces air out of the pump cavity
and into the vent system. When the solenoid is ener-
gized and de-energized, the cycle is repeated creating
flow in typical diaphragm pump fashion. The pump
is controlled 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 time.
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 7.5 inches
of water.
When the pump starts, the cycle rate is quite high.
As the system becomes pressurized pump rate drops. If
there is no leak the pump will quit. If there is a leak,
the test is terminated at the end of the test mode.
If there is no leak, the purge monitor is run. If the
cycle rate increases due to the flow through the
purge system, the test is passed and 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.
A typical system schematic is shown in (Fig. 3).
Fig. 2 Duty Cycle EVAP Canister Purge Solenoid
Location
1 - RIGHT-FRONT FENDER
2 - LDP FILTER
3 - DUTY CYCLE SOLENOID
4 - ELEC. CONNEC.
5 - LEAK DETECTION PUMP (LDP) (IF EQUIPPED)
6 - LDP ELEC. CONNEC.
BR/BEEVAPORATIVE EMISSIONS 25 - 33
EVAP/PURGE SOLENOID (Continued)

INSTALLATION - WHEEL COVERS
(1) Install cover on wheel by hand only (Fig. 20).
(2) Install and torque wheel nuts to 135 N´m (100
lb. ft.).
(3) Install nut caps, if equipped using lug wrench,
do not over tighten.
(4) Remove release liner from removal instructions
label and install label next to jacking instructions
label. Surface must be clean and flat for proper adhe-
sion of label.
EXTERIOR
INSPECTIONÐBODY SEALING
Visually inspect the following seals during the nor-
mal recommended wash. Look for areas where water
may have entered the vehicle.
²Door and window seals
²Windshield
²Backlight
INSPECTION - FIT AND FINISH
(1) Remove all protective coatings/covers.
²Remove protective film from body moldings.
(2) Make sure body is free from paint chips,
scratches, sags, run, dirt or corrosion. Touch up any
minor paint chips and scratches as required.
(3) Ensure that moldings and stripes are aligned
properly.
²Ensure that moldings and stripes are present
and securely fastened to the body.NOTE: Painted-on accent strips require a unique
paint for touch-ups.
(4) Check that the door panels have even gaps and
fit well with adjacent body panels (Fig. 21).
(5) Check that the tailgate has even gaps and fits
well with adjacent panels (Fig. 22).
Fig. 20 WHEEL COVER
Fig. 21 DOOR ALIGNMENT
Fig. 22 TAILGATE ALIGNMENT
30 - 10 NEW VEHICLE PREPARATIONBR/BE
UNDER VEHICLE (Continued)