Y case DODGE RAM 1500 1998 2.G Workshop Manual

SELECTOR SWITCH
DESCRIPTION
The selector switch assembly (Fig. 95) is mounted
in the left side of the vehicle's Instrument Panel (IP)
and consists of a rotary knob connected to a resistive
network for the mode and range shift selections. Also
located in this assembly is a recessed, normally open
momentary switch for making shifts into and out of
transfer case NEUTRAL. A pen, or similar instru-
ment, is used to make a NEUTRAL shift selection,
thus reducing the likelihood of an inadvertent shift
request.
The selector switch also contains four light emit-
ting diode's (LED's) to indicate the transfer case posi-
tion and whether a shift is in progress.
OPERATION
As the position of the selector switch varies, the
resistance between the Mode Sensor supply voltage
pin and the Mode Sensor output will vary. Hardware,
software, and calibrations within the Transfer Case
Control Module (TCCM) are provided that interpret
the selector switch resistance as given in the table
below: SELECTOR SWITCH INTERPRETATION
SELECTOR SWITCH INTERPRETATION
Step Resistance
Range (ohms)Required
Interpretation
A <200 Shorted
B 400-700 NEUTRAL
C 1050-1450 4LO
D 1850-2300 4HI
E 3050-5950 2WD (Default)
F 9.5-12.5K In between
positions
G >15.5K Open
For resistances between the ranges B-E shown for
each valid position (T-Case NEUTRAL, 4LO, 4HI,
2WD), the TCCM may interpret the resistance as:
²either of the neighboring valid positions.
²as an invalid fault position.
For resistances between the ranges E and F shown
for 2WD and in-between positions, the TCCM may
interpret the resistance as:
²the 2WD position.
²an invalid fault position.
²a valid in-between position.
For resistances between the ranges F and G shown
for in-between positions and fault condition (open),
the TCCM may interpret the resistance as:
²a valid in-between position.
²an invalid fault position.
For resistances between the ranges A and B shown
for the fault condition (short) and , T-Case NEU-
TRAL, the TCCM may interpret the resistance as:
²the T-Case NEUTRAL position.
²an invalid fault position.
The LED's in the selector assembly are illuminat-
ed/flashed in the following manner to indicate a par-
ticular condition or state.
²A solidly illuminated LED indicates a success-
fully completed shift and the current operating mode
of the transfer case. While a shift has been requested
but not yet completed, the LED for the desired trans-
fer case position is flashed.
²A flashing operating mode LED for the desired
gear indicates that a shift to that position has been
requested, but all of the driver controllable conditions
Fig. 95 Transfer Case Selector Switch
1 - SELECTOR SWITCH
21 - 574 TRANSFER CASE - NV273DR

have not been met. This is in an attempt to notify
the driver that the transmission needs to be put into
NEUTRAL, the vehicle speed is too great, or some
other condition outlined (other than a diagnostic fail-
ure that would prevent this shift) elsewhere (Refer to
8 - ELECTRICAL/ELECTRONIC CONTROL MOD-
ULES/TRANSFER CASE CONTROL MODULE -
OPERATION) is not met. Note that this flashing will
continue indefinitely until the conditions are eventu-
ally met, or the selector switch position is changed,
or if diagnostic routines no longer allow the
requested shift.
²
If the driver attempts to make a shift into transfer
case NEUTRAL, and any of the driver controllable con-
ditions are not met, the request will be ignored until all
of the conditions are met or until the NEUTRAL select
button is released. Additionally the neutral lamp will
flash, or begin to flash while the button is depressed
and operator controllable conditions are not being met.
All of the LED's except the Neutral will flash if any of
the operator controllable conditions for shifting are not
met while the Neutral button is depressed. This9toggle9
type of feature is necessary because the TCCM would
interpret another request immediately after the shift
into transfer case NEUTRAL has completed.
²No LED's illuminated indicate a fault in the
transfer case control system.
SHIFT MOTOR
DESCRIPTION
The shift motor (Fig. 96) consists of a permanent
magnet D.C. motor with gear reduction to convert a
high speed-low torque device into a low speed-high
torque device. The output of the device is coupled to
a shaft which internally moves the mode and range
forks that change the transfer case operating ranges.
The motor is rated at 25 amps maximum at 72É F
with 10 volts at the motor leads.
OPERATION
The transfer case shift motor responds to the
Transfer Case Control Module (TCCM) commands to
move the transfer case shift sector bi-directionally, as
required, to obtain the transfer case operating mode
indicated by the instrument panel mounted selector
switch.
REMOVAL
NOTE: New shift motor assemblies are shipped in
the 2WD/AWD position. If a new shift motor assem-
bly will be installed, it will be necessary to shift the
transfer case to the 2WD/AWD position prior to
motor removal.(1) Raise the vehicle on a suitable hoist.
(2) Disengage the wiring connectors from the shift
motor and mode sensor.
(3) Remove the bolts holding the shift motor and
mode sensor assembly onto the transfer case.
(4) Separate the shift motor and mode sensor
assembly from the transfer case.
INSTALLATION
(1) Verify that the shift sector o-ring is clean and
properly positioned over the shift sector and against
the transfer case.
NOTE: Verify that the shift motor position and sec-
tor shaft orientation are aligned. It may be neces-
sary to manually shift the transfer case if the shift
motor and sector shaft are not aligned.
(2) Position the shift motor and mode sensor
assembly onto the transfer case.
(3) Install the bolts to hold the assembly onto the
transfer case. Tighten the bolts to 16-24 N´m (12-18
ft.lbs.).
CAUTION: If the original shift motor and mode sen-
sor assembly bolts are reused, be sure to use
MoparTLock & Seal or LoctiteŸ 242 to replenish
the lock patch material originally found on the bolts
(4) Engage the wiring connectors to the shift motor
and mode sensor.
(5) Refill the transfer case as necessary.
(6) Lower vehicle and verify transfer case
operation.
Fig. 96 Shift Motor - Shown Inverted - Typical
1 - SHIFT MOTOR
DRTRANSFER CASE - NV273 21 - 575
SELECTOR SWITCH (Continued)

TIRES
DESCRIPTION
DESCRIPTION - SPARE TIRE / TEMPORARY
The temporary spare tire is designed for emer-
gency use only. The original tire should be repaired
or replaced at the first opportunity, then reinstalled.
Do not exceed speeds of 50 M.P.H. when using the
temporary spare tire. Refer to Owner's Manual for
complete details.
DESCRIPTION - TIRES
Tires are designed and engineered for each specific
vehicle. They provide the best overall performance
for normal operation. The ride and handling charac-
teristics match the vehicle's requirements. With
proper care they will give excellent reliability, trac-
tion, skid resistance, and tread life.
Driving habits have more effect on tire life than
any other factor. Careful drivers will obtain in most
cases, much greater mileage than severe use or care-
less drivers. A few of the driving habits which will
shorten the life of any tire are:
²Rapid acceleration
²Severe brake applications
²High speed driving
²Excessive speeds on turns
²Striking curbs and other obstacles
Radial-ply tires are more prone to irregular tread
wear. It is important to follow the tire rotation inter-
val shown in the section on Tire Rotation, (Refer to
22 - TIRES/WHEELS - STANDARD PROCEDURE).
This will help to achieve a greater tread life.
TIRE IDENTIFICATION
Tire type, size, aspect ratio and speed rating are
encoded in the letters and numbers imprinted on the
side wall of the tire. Refer to the chart to decipher
the tire identification code (Fig. 11).
Performance tires have a speed rating letter after
the aspect ratio number. The speed rating is not
always printed on the tire sidewall. These ratings
are:
²Qup to 100 mph
²Rup to 106 mph
²Sup to 112 mph
²Tup to 118 mph
²Uup to 124 mph
²Hup to 130 mph
²Vup to 149 mph
²Zmore than 149 mph (consult the tire manu-
facturer for the specific speed rating)An All Season type tire will have eitherM+S,M
&SorM±S(indicating mud and snow traction)
imprinted on the side wall.
TIRE CHAINS
Tire snow chains may be used oncertainmodels.
Refer to the Owner's Manual for more information.
DESCRIPTION - RADIAL ± PLY TIRES
Radial-ply tires improve handling, tread life and
ride quality, and decrease rolling resistance.
Radial-ply tires must always be used in sets of
four. Under no circumstances should they be used on
the front only. They may be mixed with temporary
spare tires when necessary. A maximum speed of 50
MPH is recommended while a temporary spare is in
use.
Radial-ply tires have the same load-carrying capac-
ity as other types of tires of the same size. They also
use the same recommended inflation pressures.
The use of oversized tires, either in the front or
rear of the vehicle, can cause vehicle drive train fail-
ure. This could also cause inaccurate wheel speed
signals when the vehicle is equipped with Anti-Lock
Brakes.
The use of tires from different manufactures on the
same vehicle is NOT recommended. The proper tire
pressure should be maintained on all four tires.
Fig. 11 Tire Identification
22 - 6 TIRES/WHEELSDR

WHEELS
DESCRIPTION
Original equipment wheels are designed for the
specified Maximum Vehicle Capacity.
All models use steel or aluminum drop center
wheels.
Aluminum wheels require special balance weights
and alignment equipment.
(1) On vehicles equipped with dual rear wheels,
The rim is an eight stud hole pattern wheel. The
wheels have a flat mounting surface (Fig. 18). The
slots in the wheel must be aligned to provide access
to the valve stem (Fig. 19).
OPERATION
The wheel (Fig. 20) has raised sections between
the rim flanges and the rim well. Initial inflation of
the tire forces the bead over these raised sections. In
case of tire failure, the raised sections hold the tire
in position on the wheel until the vehicle can be
brought to a safe stop.
DIAGNOSIS AND TESTING
WHEEL INSPECTION
Inspect wheels for:
²Excessive run out
²Dents or cracks
²Damaged wheel lug nut holes
²Air Leaks from any area or surface of the rim
NOTE: Do not attempt to repair a wheel by hammer-
ing, heating or welding.
If a wheel is damaged an original equipment
replacement wheel should be used. When obtaining
replacement wheels, they should be equivalent in
load carrying capacity. The diameter, width, offset,
pilot hole and bolt circle of the wheel should be the
same as the original wheel.
WARNING: FAILURE TO USE EQUIVALENT
REPLACEMENT WHEELS MAY ADVERSELY
AFFECT THE SAFETY AND HANDLING OF THE
VEHICLE. USED WHEELS ARE NOT RECOM-
MENDED. THE SERVICE HISTORY OF THE WHEEL
MAY HAVE INCLUDED SEVERE TREATMENT OR
VERY HIGH MILEAGE. THE RIM COULD FAIL WITH-
OUT WARNING.
Fig. 18 FLAT FACE WHEEL
1 - FLAT FACE
2 - VALVE STEM
Fig. 19 DUAL REAR WHEELS
1 - WINDOW OPENINGS (5)
2 - INBOARD VALVE STEM
3 - OUTBOARD VALVE STEM
Fig. 20 Safety Rim
1 - FLANGE
2 - RIDGE
3 - WELL
DRTIRES/WHEELS 22 - 11

NOTE: The air gap is determined by the spacer
shims. When installing an original, or a new clutch
assembly, try the original shims first. When install-
ing a new clutch onto a compressor that previously
did not have a clutch, use a 1.0, 0.50, and 0.13 mil-
limeter (0.040, 0.020, and 0.005 inch) shims from the
new clutch hardware package that is provided with
the new clutch.
(9) To complete the procedure (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING/A/C COM-
PRESSOR - INSTALLATION).
A/C COMPRESSOR CLUTCH
RELAY
DESCRIPTION
The A/C compressor clutch relay (Fig. 10) is a
International Standards Organization (ISO) micro-re-
lay. Relays conforming to the ISO specifications have
common physical dimensions, current capacities, ter-
minal patterns, and terminal functions. The ISO
micro-relay terminal functions are the same as a con-
ventional ISO relay. However, the ISO micro-relay
terminal pattern (or footprint) is different, the cur-
rent capacity is lower, and the physical dimensions
are smaller than those of the conventional ISO relay.
The A/C compressor clutch relay is located in the
intergrated power module (IPM) in the engine com-
partment. See the fuse and relay layout label affixed
to the inside surface of the IPM cover for A/C com-
pressor clutch relay identification and location.
The black, molded plastic case is the most visible
component of the A/C compressor clutch relay. Fivemale spade-type terminals extend from the bottom of
the base to connect the relay to the vehicle electrical
system, and the ISO designation for each terminal is
molded into the base adjacent to each terminal. The
ISO terminal designations are as follows:
²30 (Common Feed)- This terminal is con-
nected to the movable contact point of the relay.
²85 (Coil Ground)- This terminal is connected
to the ground feed side of the relay control coil.
²86 (Coil Battery)- This terminal is connected
to the battery feed side of the relay control coil.
²87 (Normally Open)- This terminal is con-
nected to the normally open fixed contact point of the
relay.
²87A (Normally Closed)- This terminal is con-
nected to the normally closed fixed contact point of
the relay.
OPERATION
The A/C compressor clutch relay is an electrome-
chanical switch that uses a low current input from
the powertrain control module (PCM) or engine con-
trol module (ECM) depending on engine application,
to control the high current output to the compressor
clutch electromagnetic coil. The movable common
feed contact point is held against the fixed normally
closed contact point by spring pressure. When the
relay coil is energized, an electromagnetic field is
produced by the coil windings. This electromagnetic
field draws the movable relay contact point away
from the fixed normally closed contact point, and
holds it against the fixed normally open contact
point. When the relay coil is de-energized, spring
pressure returns the movable contact point back
against the fixed normally closed contact point. The
resistor or diode is connected in parallel with the
relay coil in the relay, and helps to dissipate voltage
Fig. 9 Check Clutch Air Gap - Typical
1 - FEELER GAUGE
Fig. 10 A/C Compressor Clutch Micro-Relay
30 - COMMON FEED
85 - COIL GROUND
86 - COIL BATTERY
87 - NORMALLY OPEN
87A - NORMALLY CLOSED
DRCONTROLS 24 - 13
A/C COMPRESSOR CLUTCH/COIL (Continued)

DIAGNOSIS AND TESTING - BLOWER MOTOR
RESISTOR BLOCK
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
For circuit descriptions and diagrams, refer to the
appropriate wiring information. The wiring informa-
tion includes wiring diagrams, proper wire and con-
nector repair procedures, further details on wire
harness routing and retention, as well as pin-out and
location views for the various wire harness connec-
tors, splices and grounds.
(1) Disconnect and isolate the negative battery
cable.
(2) Disconnect the wire harness connector from the
blower motor resistor block.
(3) Check for continuity between each of the
blower motor switch input terminals of the resistor
and the resistor output terminal. In each case there
should be continuity. If OK, repair the wire harness
circuits between the blower motor switch and blower
motor resistor or blower motor as required. If not
OK, replace the faulty blower motor resistor block.
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.CAUTION: Stay clear of the blower motor resistor
block heat sink (Hot). Do not operate the blower
motor with the resistor block removed.
(1) Disconnect and isolate the negative battery
cable.
(2) Reach under the instrument panel near the
blower motor and disconnect the wire harness con-
nector from the blower motor resistor block.
(3) Remove the two screws that secure the blower
motor resistor block to the HVAC housing.
(4) Remove the resistor block from the HVAC
housing.
INSTALLATION
(1) Position the blower motor resistor block into
the HVAC housing.
(2) Install the two screws that secure the resistor
block to the HVAC housing. Tighten the screws to 2.2
N´m (20 in. lbs.).
(3) Connect the wire harness connector to the
resistor block.
(4) Reconnect the battery negative cable.
Fig. 17 Blower Motor Resistor Block
1 - SCREW (2)
2 - WIRE HARNESS CONNECTOR
3 - HVAC HOUSING
4 - BLOWER MOTOR RESISTOR BLOCK
5 - BLOWER MOTOR
DRCONTROLS 24 - 19
BLOWER MOTOR RESISTOR BLOCK (Continued)

NOTE: The instrument panel air outlets are retained
into the outlet housings by a light snap fit.
(1) Using a trim stick or another suitable wide
flat-bladed tool, gently pry the panel air outlet(s) out
of the panel outlet housing(s) as required (Fig. 1).
INSTALLATION
(1) Position the air outlet(s) onto the outlet hous-
ing(s).
(2) Gently push the air outlet into the housing
until it snaps into position.
BLEND DOOR
REMOVAL
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, DISABLE THE AIRBAG SYSTEM BEFORE
ATTEMPTING ANY STEERING WHEEL, STEERING
COLUMN, OR INSTRUMENT PANEL COMPONENT
DIAGNOSIS OR SERVICE. DISCONNECT AND ISO-
LATE THE BATTERY NEGATIVE (GROUND) CABLE,
THEN WAIT TWO MINUTES FOR THE AIRBAG SYS-
TEM CAPACITOR TO DISCHARGE BEFORE PER-
FORMING FURTHER DIAGNOSIS OR SERVICE. THIS
IS THE ONLY SURE WAY TO DISABLE THE AIRBAG
SYSTEM. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN AN ACCIDENTAL
AIRBAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.NOTE: Vehicles equiped with single zone HVAC
systems have one blend door, dual zone systems
have two blend doors.
(1) Remove the HVAC housing from the vehicle
(Refer to 24 - HEATING & AIR CONDITIONING/
DISTRIBUTION/HVAC HOUSING - REMOVAL).
(2) Disassemble the HVAC housing (Refer to 24 -
HEATING & AIR CONDITIONING/DISTRIBUTION/
HVAC HOUSING - DISASSEMBLY).
(3) Remove the levers from the driver and/or pas-
senger side blend door (if equipped) (Fig. 2).
(4) Gently slide the drivers and/or passenger side
blend door toward the out side of the housing. Tilt
and lift the door(s) out of the housing.
(5) Inspect the blend door(s), seals and the HVAC
housing for damage or binding and repair or replace
components as required.
INSTALLATION
(1) Position the blend door pivot shafts into the
pivot hole and actuator in the bottom of the lower
half of the HVAC housing.
(2) Install the blend door(s) by carefully tipping
the doors into the HVAC housing, then sliding each
door into it's operating position.
(3) Install the levers to the driver and/or passen-
ger side blend door (if equipped).
(4) Assemble the HVAC housing (Refer to 24 -
HEATING & AIR CONDITIONING/DISTRIBUTION/
HVAC HOUSING - ASSEMBLY)
Fig. 1 Instrument Panel Air Outlets
1 - HEADLIGHT SWITCH
2 - AIR OUTLETS
3 - INSTRUMENT CLUSTER
4 - CLIMATE CONTROL
5 - RADIO
6 - AIRBAG
7 - GLOVE BOX
8 - HEATED SEAT SWITCH (IF EQUIPPED)
9 - TRANSFER CASE SWITCH (IF EQUIPPED)
10 - CIGAR LIGHTER
11 - CUP HOLDERS
12 - ASH TRAY (IF EQUIPPED)
13 - POWER OUTLET
Fig. 2 Blend Door - Dual Zone Shown, Single Zone
Typical
1 - PASSENGER SIDE BLEND DOOR LEVER
2 - PASSENGER SIDE BLEND DOOR
3 - EVAPORATOR TEMPERATURE SENSOR WIRE
4 - HVAC HOUSING
5 - A/C EVAPORATOR
6 - EVAPORATOR TEMPERATURE SENSOR PROBE
7 - DRIVER SIDE BLEND DOOR
8 - DRIVER SIDE BLEND DOOR LEVER
DRDISTRIBUTION 24 - 27
AIR OUTLETS (Continued)

O2S is used to detect the amount of oxygen in the
exhaust gas before the gas enters the catalytic con-
verter. The PCM calculates the A/F mixture from the
output of the O2S. A low voltage indicates high oxy-
gen content (lean mixture). A high voltage indicates a
low content of oxygen (rich mixture).
When the upstream O2S detects a lean condition,
there is an abundance of oxygen in the exhaust gas.
A functioning converter would store this oxygen so it
can use it for the oxidation of HC and CO. As the
converter absorbs the oxygen, there will be a lack of
oxygen downstream of the converter. The output of
the downstream O2S will indicate limited activity in
this condition.
As the converter loses the ability to store oxygen,
the condition can be detected from the behavior of
the downstream O2S. When the efficiency drops, no
chemical reaction takes place. This means the con-
centration of oxygen will be the same downstream as
upstream. The output voltage of the downstream
O2S copies the voltage of the upstream sensor. The
only difference is a time lag (seen by the PCM)
between the switching of the O2S's.
To monitor the system, the number of lean-to-rich
switches of upstream and downstream O2S's is
counted. The ratio of downstream switches to
upstream switches is used to determine whether the
catalyst is operating properly. An effective catalyst
will have fewer downstream switches than it has
upstream switches i.e., a ratio closer to zero. For a
totally ineffective catalyst, this ratio will be one-to-
one, indicating that no oxidation occurs in the device.
The system must be monitored so that when cata-
lyst efficiency deteriorates and exhaust emissions
increase to over the legal limit, the MIL will be illu-
minated.
DESCRIPTION - TRIP DEFINITION
The term ªTripº has different meanings depending
on what the circumstances are. If the MIL (Malfunc-
tion Indicator Lamp) is OFF, a Trip is defined as
when the Oxygen Sensor Monitor and the Catalyst
Monitor have been completed in the same drive cycle.
When any Emission DTC is set, the MIL on the
dash is turned ON. When the MIL is ON, it takes 3
good trips to turn the MIL OFF. In this case, it
depends on what type of DTC is set to know what a
ªTripº is.
For the Fuel Monitor or Mis-Fire Monitor (contin-
uous monitor), the vehicle must be operated in the
ªSimilar Condition Windowº for a specified amount of
time to be considered a Good Trip.If a Non-Contiuous OBDII Monitor fails twice in a
row and turns ON the MIL, re-running that monitor
which previously failed, on the next start-up and
passing the monitor, is considered to be a Good Trip.
These will include the following:
²Oxygen Sensor
²Catalyst Monitor
²Purge Flow Monitor
²Leak Detection Pump Monitor (if equipped)
²EGR Monitor (if equipped)
²Oxygen Sensor Heater Monitor
If any other Emission DTC is set (not an OBDII
Monitor), a Good Trip is considered to be when the
Oxygen Sensor Monitor and Catalyst Monitor have
been completed; or 2 Minutes of engine run time if
the Oxygen Sensor Monitor or Catalyst Monitor have
been stopped from running.
It can take up to 2 Failures in a row to turn on the
MIL. After the MIL is ON, it takes 3 Good Trips to
turn the MIL OFF. After the MIL is OFF, the PCM
will self-erase the DTC after 40 Warm-up cycles. A
Warm-up cycle is counted when the ECT (Engine
Coolant Temperature Sensor) has crossed 160ÉF and
has risen by at least 40ÉF since the engine has been
started.
DESCRIPTION - COMPONENT MONITORS
There are several components that will affect vehi-
cle emissions if they malfunction. If one of these com-
ponents malfunctions the Malfunction Indicator
Lamp (MIL) will illuminate.
Some of the component monitors are checking for
proper operation of the part. Electrically operated
components now have input (rationality) and output
(functionality) checks. Previously, a component like
the Throttle Position sensor (TPS) was checked by
the PCM for an open or shorted circuit. If one of
these conditions occurred, a DTC was set. Now there
is a check to ensure that the component is working.
This is done by watching for a TPS indication of a
greater or lesser throttle opening than MAP and
engine rpm indicate. In the case of the TPS, if engine
vacuum is high and engine rpm is 1600 or greater,
and the TPS indicates a large throttle opening, a
DTC will be set. The same applies to low vacuum if
the TPS indicates a small throttle opening.
All open/short circuit checks, or any component
that has an associated limp-in, will set a fault after 1
trip with the malfunction present. Components with-
out an associated limp-in will take two trips to illu-
minate the MIL.
25 - 4 EMISSIONS CONTROLDR
EMISSIONS CONTROL (Continued)

CCV HOSE
DESCRIPTION - 8.0L V-10
The 8.0L V-10 engine is equipped with a Crankcase
Ventilation (CCV) system. The CCV system performs
the same function as a conventional PCV system, but
does not use a vacuum controlled valve (PCV valve).
A molded vacuum tube connects manifold vacuum
to the top of the right cylinder head (valve) cover.
The vacuum tube connects to a fixed orifice fitting
(Fig. 2) of a calibrated size 2.6 mm (0.10 inches).
OPERATION - 8.0L V-10
A molded vacuum tube connects manifold vacuum
to the top of the right cylinder head (valve) cover.
The vacuum tube connects to a fixed orifice fitting
(Fig. 2) of a calibrated size 2.6 mm (0.10 inches). The
fitting meters the amount of crankcase vapors drawn
out of the engine.The fixed orifice fitting is grey
in color.A similar fitting (but does not contain a
fixed orifice) is used on the left cylinder head (valve)
cover. This fitting is black in color. Do not inter-
change these two fittings.
When the engine is operating, fresh air enters the
engine and mixes with crankcase vapors. Manifold
vacuum draws the vapor/air mixture through the
fixed orifice and into the intake manifold. The vapors
are then consumed during engine combustion.
EVAP/PURGE SOLENOID
DESCRIPTION
The duty cycle EVAP canister purge solenoid is
located in the engine compartment. It is attached to
the side of the Power Distribution Center (PDC).
OPERATION
The Powertrain Control Module (PCM) operates
the solenoid.
During the cold start warm-up period and the hot
start time delay, the PCM does not energize the sole-
noid. When de-energized, no vapors are purged. The
PCM de-energizes the solenoid during open loop oper-
ation.
The engine enters closed loop operation after it
reaches a specified temperature and the time delay
ends. During closed loop operation, the PCM ener-
gizes and de-energizes the solenoid 5 or 10 times per
second, depending upon operating conditions. The
PCM varies the vapor flow rate by changing solenoid
pulse width. Pulse width is the amount of time the
solenoid energizes. The PCM adjusts solenoid pulse
width based on engine operating condition.
REMOVAL
The duty cycle EVAP canister purge solenoid is
located in the engine compartment. It is attached to
the side of the Power Distribution Center (PDC) (Fig.
3).
(1) Disconnect electrical wiring connector at sole-
noid.
(2) Disconnect vacuum harness at solenoid (Fig. 3).
(3) Remove solenoid from mounting bracket.
INSTALLATION
(1) Install solenoid assembly to mounting bracket.
(2) Connect vacuum harness.
(3) Connect electrical connector.
Fig. 2 FIXED ORIFICE FITTING - 8.0L V-10 ENGINE -
TYPICAL
1 - VACUUM TUBE
2 - FIXED ORIFICE FITTING
3 - COIL PACKS
4 - ORIFICE FITTING HOSE CONNECTIONS
25 - 12 EVAPORATIVE EMISSIONSDR

Check the vapor/vacuum lines at the LDP, LDP
filter and EVAP canister purge solenoid for
damage or leaks. If a leak is present, a Diagnos-
tic Trouble Code (DTC) may be set.
(4) Connect electrical connector to LDP.
ORVR
DESCRIPTION
The ORVR (On-Board Refueling Vapor Recovery)
system consists of a unique fuel tank, flow manage-
ment valve, fluid control valve, one-way check valve
and vapor canister.
OPERATION
The ORVR (On-Board Refueling Vapor Recovery)
system is used to remove excess fuel tank vapors.
This is done while the vehicle is being refueled.
Fuel flowing into the fuel filler tube (approx. 1º
I.D.) creates an aspiration effect drawing air into the
fuel fill tube. During refueling, the fuel tank is
vented to the EVAP canister to capture escaping
vapors. With air flowing into the filler tube, there are
no fuel vapors escaping to the atmosphere. Once the
refueling vapors are captured by the EVAP canister,
the vehicle's computer controlled purge system draws
vapor out of the canister for the engine to burn. The
vapor flow is metered by the purge solenoid so that
there is no, or minimal impact on driveability or
tailpipe emissions.
As fuel starts to flow through the fuel fill tube, it
opens the normally closed check valve and enters the
fuel tank. Vapor or air is expelled from the tank
through the control valve and on to the vapor canis-
ter. Vapor is absorbed in the EVAP canister until
vapor flow in the lines stops. This stoppage occurs
following fuel shut-off, or by having the fuel level in
the tank rise high enough to close the control valve.
This control valve contains a float that rises to seal
the large diameter vent path to the EVAP canister.
At this point in the refueling process, fuel tank pres-
sure increases, the check valve closes (preventing liq-
uid fuel from spiting back at the operator), and fuel
then rises up the fuel filler tube to shut off the dis-
pensing nozzle.
PCV VALVE
DESCRIPTION
3.7L V-6 / 4.7L V-8
The 3.7L V-6 and 4.7L V-8 engines are equipped
with a closed crankcase ventilation system and a
Positive Crankcase Ventilation (PCV) valve.
This system consists of:
²a PCV valve mounted to the oil filler housing
(Fig. 10). 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. 11).
²tubes and hoses to connect the system compo-
nents.
Fig. 10 PCV VALVE - 3.7L V-6 / 4.7L V-8
1 - O-RING
2 - LOCATING TABS
3 - CAM LOCK
4 - OIL FILLER TUBE
5 - PCV LINE/HOSE
6 - P C V VA LV E
DREVAPORATIVE EMISSIONS 25 - 17
LEAK DETECTION PUMP (Continued)