1998 DODGE RAM 1500 no start modes

During Closed Loop modes, the PCM will monitor
the oxygen (O2S) sensors input. This input indicates
to the PCM whether or not the calculated injector
pulse width results in the ideal air-fuel ratio. This
ratio is 14.7 parts air-to-1 part fuel. By monitoring
the exhaust oxygen content through the O2S sensor,
the PCM can fine tune the injector pulse width. This
is done to achieve optimum fuel economy combined
with low emission engine performance.
The fuel injection system has the following modes
of operation:
²Ignition switch ON
²Engine start-up (crank)
²Engine warm-up
²Idle
²Cruise
²Acceleration
²Deceleration
²Wide open throttle (WOT)
²Ignition switch OFF
The ignition switch On, engine start-up (crank),
engine warm-up, acceleration, deceleration and wide
open throttle modes are Open Loop modes. The idle
and cruise modes, (with the engine at operating tem-
perature) are Closed Loop modes.
IGNITION SWITCH (KEY-ON) MODE
This is an Open Loop mode. When the fuel system
is activated by the ignition switch, the following
actions occur:
²The PCM pre-positions the idle air control (IAC)
motor.
²The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
²The PCM monitors the engine coolant tempera-
ture sensor input. The PCM modifies fuel strategy
based on this input.
²Intake manifold air temperature sensor input is
monitored.
²Throttle position sensor (TPS) is monitored.
²The auto shutdown (ASD) relay is energized by
the PCM for approximately three seconds.
²The fuel pump is energized through the fuel
pump relay by the PCM. The fuel pump will operate
for approximately three seconds unless the engine is
operating or the starter motor is engaged.
²The O2S sensor heater element is energized via
the ASD or O2S heater relay. The O2S sensor input
is not used by the PCM to calibrate air-fuel ratio dur-
ing this mode of operation.
ENGINE START-UP MODE
This is an Open Loop mode. The following actions
occur when the starter motor is engaged.
The PCM receives inputs from:²Battery voltage
²Engine coolant temperature sensor
²Crankshaft position sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
The PCM monitors the crankshaft position sensor.
If the PCM does not receive a crankshaft position
sensor signal within 3 seconds of cranking the
engine, it will shut down the fuel injection system.
The fuel pump is activated by the PCM through
the fuel pump relay.
Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.
The PCM determines the proper ignition timing
according to input received from the crankshaft posi-
tion sensor.
ENGINE WARM-UP MODE
This is an Open Loop mode. During engine warm-
up, the PCM receives inputs from:
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
²Park/neutral switch (gear indicator signalÐauto.
trans. only)
²Air conditioning select signal (if equipped)
²Air conditioning request signal (if equipped)
Based on these inputs the following occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off.
²The PCM adjusts engine idle speed through the
idle air control (IAC) motor and adjusts ignition tim-
ing.
²The PCM operates the A/C compressor clutch
through the A/C compressor clutch relay. This is done
if A/C has been selected by the vehicle operator and
specified pressures are met at the high and low±pres-
sure A/C switches. Refer to Heating and Air Condi-
tioning for additional information.
²When engine has reached operating tempera-
ture, the PCM will begin monitoring O2S sensor
input. The system will then leave the warm-up mode
and go into closed loop operation.
8E - 8 ELECTRONIC CONTROL MODULESDR
POWERTRAIN CONTROL MODULE (Continued)

TRANSFER CASE CONTROL
MODULE
DESCRIPTION
The Transfer Case Control Module (TCCM) (Fig. 8)
is a microprocessor-based assembly, controlling the
4X4 transfer case shift functions via the actuation of
a shift motor and utilizing the feedback of a mode
sensor assembly. Communication is via the PCI serial
bus. Inputs include user selectable 4X4 modes that
include 2WD, AWD, 4HI, 4LO, and Neutral. The logic
and driver circuitry is contained in a molded plastic
housing with an embedded heat-sink and is located
behind the left side of the lower instrument panel.
OPERATION
The Transfer Case Control Module (TCCM) utilizes
the input from the transfer case mounted mode sen-
sor, the instrument panel mounted selector switch,
and the following information from the vehicle's PCI
serial bus to determine if a shift is allowed.
²Engine RPM and Vehicle Speed
²Diagnostic Requests
²Manual Transmission and Brake Applied
²PRNDL
²Ignition Status
²ABS Messages
Once the TCCM determines that a requested shift
is allowed, it actuates the bi-directional shift motor
as necessary to achieve the desired transfer case
operating mode. The TCCM also monitors the mode
sensor while controlling the shift motor to determine
the status of the shift attempt.Several items can cause the requested shift not to
be completed. If the TCCM has recognized a fault
(DTC) of some variety, it will begin operation in one
of four Functionality Levels. These levels are:
²Level Zero- Normal Operation.
²Level One- Only Mode Shifts Are Allowed.
²Level Two- Only Mode Shifts and Shifts Into
LOW Are Allowed (No Neutral Shifts Are Allowed).
²Level Three- No Shifts Are Allowed
The TCCM can also be operating in one of three
possible power modes. These power modes are:
²Full Power Modeis the normal operational
mode of the module. This mode is achieved by normal
PCI bus traffic being present and the ignition being
in the RUN position.
²Reduced Power Modewill be entered when
the ignition has been powered off. In this state, the
module will shut down power supplied to external
devices, and to electronic interface inputs and out-
puts. From this state the module can enter either
Sleep Mode or Full Power Mode. To enter this mode,
the module must receive an ignition message denot-
ing that the ignition is off, or not receive any mes-
sages for 5  0.5 seconds. To exit this mode, the
module must receive one ignition message that
denotes that the ignition is in the RUN position.
²Sleep Modewill be entered, from the Reduced
Power Mode, when no PCI traffic has been sensed for
20  1 seconds. If during Sleep Mode the module
detects PCI bus traffic, it will revert to the Reduced
Power mode while monitoring for ignition messages.
It will remain in this state as long as there is traffic
other than run or start messages, and will return to
Sleep mode if the bus goes without traffic for 20  1
seconds.
SHIFT REQUIREMENTS
If the TCCM is in full power mode and at function-
ality level zero, it uses the following criteria to deter-
mine if a shift is allowed.
If any of the driver controllable conditions are not
met once the shift request is recognized, the TCCM
will solidly illuminate the source position's LED and
flash the desired position's LED for all shifts except
NEUTRAL. The NEUTRAL shift LED strategy will
be discussed later.
Mode shiftswill be allowed regardless of trans-
mission gear or vehicle speed, whenever the following
conditions are met:
²Front and rear wheel speed are within 21 km/hr
(13 mph).
²A change in the Selector switch state indicates
that a mode shift has been requested.
²A valid mode sensor signal is being sensed by
the TCCM.
Fig. 8 Transfer Case Control Module (TCCM)
Location
1 - INSTRUMENT PANEL
2 - TRANSFER CASE CONTROL MODULE (TCCM)
3 - TRANSFER CASE SELECTOR SWITCH
8E - 16 ELECTRONIC CONTROL MODULESDR

²Exterior Lighting Fail-safe- In the absence of
a headlamp switch input, the EMIC will turn on the
cluster illumination lamps and provide electronic
headlamp low beam and park lamp request messages
to the Front Control Module (FCM) located on the
Integrated Power Module (IPM) for default exterior
lamp operation. The FCM will also provide default
park lamp and headlamp low beam operation and the
EMIC will turn on the cluster illumination lamps if
there is a failure of the electronic data bus commu-
nication between the EMIC and the FCM.
²Heated Seat Control- The EMIC monitors
inputs from the ignition switch and electronic engine
speed messages from the Powertrain Control Module
(PCM) to control a high side driver output to the
heated seat switch Light Emitting Diode (LED) indi-
cators. This input allows the heated seat switches to
wake up the heated seat module if the switch is actu-
ated. The EMIC will de-energize the heated seat
switch LED indicators, which deactivates the heated
seat system, if the ignition switch is turned to any
position except On or Start, or if the engine speed
message indicates zero. (Refer to 8 - ELECTRICAL/
HEATED SEATS - DESCRIPTION).
²Interior Lamp Load Shedding- The EMIC
provides a battery saver feature which will automat-
ically turn off all interior lamps that remain on after
a timed interval of about fifteen minutes.
²Interior Lamps - Enhanced Accident
Response- The EMIC monitors inputs from the Air-
bag Control Module (ACM) and the Powertrain Con-
trol Module (PCM) to automatically turn on the
interior lighting after an airbag deployment event
ten seconds after the vehicle speed is zero. The inte-
rior lighting remains illuminated until the key is
removed from the ignition switch lock cylinder, at
which time the interior lighting returns to normal
operation and control. This feature, like all other
enhanced accident response features, is dependent
upon a functional vehicle electrical system following
the vehicle impact event.
²Interior Lighting Control- The EMIC moni-
tors inputs from the interior lighting switch, the door
ajar switches, the cargo lamp switch, the reading
lamp switches, and the Remote Keyless Entry (RKE)
module to provide courtesy lamp control. This
includes support for timed illuminated entry with
theater-style fade-to-off and courtesy illumination
defeat features.
²Lamp Out Indicator Control- The EMIC
monitors electronic lamp outage messages from the
Front Control Module (FCM) located on the Inte-
grated Power Module (IPM) in order to provide lamp
out indicator control for the headlamps (low and high
beams), turn signal lamps, and the brake lamps
(excluding CHMSL).²Panel Lamps Dimming Control- The EMIC
provides a hard wired 12-volt Pulse-Width Modulated
(PWM) output that synchronizes the dimming level
of all hard wired panel lamps dimmer controlled
lamps with that of the cluster illumination lamps.
²Parade Mode- The EMIC provides a parade
mode (also known as funeral mode) that allows all
Vacuum-Fluorescent Display (VFD) units in the vehi-
cle to be illuminated at full (daytime) intensity while
driving during daylight hours with the exterior
lamps turned on.
²Power Locks- The EMIC monitors inputs from
the power lock switches and the Remote Keyless
Entry (RKE) receiver module (optional) to provide
control of the power lock motors through high side
driver outputs to the power lock motors. This
includes support for rolling door locks (also known as
automatic door locks), automatic door unlock, a door
lock inhibit mode, and central locking (with the
optional Vehicle Theft Security System only). (Refer
to 8 - ELECTRICAL/POWER LOCKS - DESCRIP-
TION).
²Remote Keyless Entry- The EMIC supports
the optional Remote Keyless Entry (RKE) system fea-
tures, including support for the RKE Lock, Unlock
(with optional driver-door-only unlock, and unlock-
all-doors), Panic, audible chirp, optical chirp, illumi-
nated entry modes, an RKE programming mode, as
well as optional Vehicle Theft Security System
(VTSS) arming (when the proper VTSS arming con-
ditions are met) and disarming.
²Remote Radio Switch Interface- The EMIC
monitors inputs from the optional remote radio
switches and then provides the appropriate electronic
data bus messages to the radio to select the radio
operating mode, volume control, preset station scan
and station seek features.
²Rolling Door Locks- The EMIC provides sup-
port for the power lock system rolling door locks fea-
ture (also known as automatic door locks). This
feature will automatically lock all unlocked doors
each time the vehicle speed reaches twenty-four kilo-
meters-per-hour (fifteen miles-per-hour). Following
an automatic lock event, if the driver side front door
is opened first after the ignition is turned to the Off
position, all doors will be automatically unlocked.
²Turn Signal & Hazard Warning Lamp Con-
trol- The EMIC provides electronic turn and hazard
lamp request messages to the Front Control Module
(FCM) located on the Integrated Power Module (IPM)
for turn and hazard lamp control. The EMIC also
provides an audible click at one of two rates to emu-
late normal and bulb out turn or hazard flasher oper-
ation based upon electronic lamp outage messages
from the FCM, and provides an audible turn signal
on chime warning if a turn is signalled continuously
8J - 4 INSTRUMENT CLUSTERDR
INSTRUMENT CLUSTER (Continued)

sage-controlled functions of the cluster by lighting
the appropriate indicators, positioning the gauge nee-
dles at several predetermined calibration points
across the gauge faces, and illuminating all segments
of the odometer/trip odometer and gear selector indi-
cator Vacuum-Fluorescent Display (VFD) units.
(Refer to 8 - ELECTRICAL/INSTRUMENT CLUS-
TER - DIAGNOSIS AND TESTING). See the owner's
manual in the vehicle glove box for more information
on the features, use and operation of the EMIC.
GAUGES
All gauges receive battery current through the
EMIC circuitry only when the ignition switch is in
the On or Start positions. With the ignition switch in
the Off position battery current is not supplied to
any gauges, and the EMIC circuitry is programmed
to move all of the gauge needles back to the low end
of their respective scales. Therefore, the gauges do
not accurately indicate any vehicle condition unless
the ignition switch is in the On or Start positions.
All of the EMIC gauges are air core magnetic
units. Two fixed electromagnetic coils are located
within each gauge. These coils are wrapped at right
angles to each other around a movable permanent
magnet. The movable magnet is suspended within
the coils on one end of a pivot shaft, while the gauge
needle is attached to the other end of the shaft. One
of the coils has a fixed current flowing through it to
maintain a constant magnetic field strength. Current
flow through the second coil changes, which causes
changes in its magnetic field strength. The current
flowing through the second coil is changed by the
EMIC circuitry in response to messages received over
the PCI data bus. The gauge needle moves as the
movable permanent magnet aligns itself to the
changing magnetic fields created around it by the
electromagnets.
The gauges are diagnosed using the EMIC self-di-
agnostic actuator test. (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - DIAGNOSIS AND
TESTING). Proper testing of the PCI data bus and
the electronic data bus message inputs to the EMIC
that control each gauge require the use of a DRBIIIt
scan tool. Refer to the appropriate diagnostic infor-
mation. Specific operation details for each gauge may
be found elsewhere in this service information.
VACUUM-FLUORESCENT DISPLAYS
The Vacuum-Fluorescent Display (VFD) units are
soldered to the EMIC electronic circuit board. With
the ignition switch in the Off or Accessory positions,
the odometer display is activated when the driver
door is opened (Rental Car mode) and is deactivated
when the driver door is closed. Otherwise, both dis-
play units are active when the ignition switch is inthe On or Start positions, and inactive when the igni-
tion switch is in the Off or Accessory positions.
The illumination intensity of the VFD units is con-
trolled by the EMIC circuitry based upon an input
from the headlamp switch and a dimming level input
received from the headlamp dimmer switch. The
EMIC synchronizes the illumination intensity of
other VFD units with that of the units in the EMIC
by sending electronic dimming level messages to
other electronic modules in the vehicle over the PCI
data bus.
The EMIC VFD units have several display capabil-
ities including odometer, trip odometer, engine hours,
gear selector indication (PRNDL) for models with an
automatic transmission, several warning or reminder
indications, and various diagnostic information when
certain fault conditions exist. An odometer/trip odom-
eter switch on the EMIC circuit board is used to con-
trol some of the display modes. This switch is
actuated manually by depressing the odometer/trip
odometer switch button that extends through the
lower edge of the cluster lens, just left of the tachom-
eter. Actuating this switch momentarily with the
ignition switch in the On position will toggle the
VFD between the odometer and trip odometer modes.
Depressing the switch button for about two seconds
while the VFD is in the trip odometer mode will
reset the trip odometer value to zero. While in the
odometer mode with the ignition switch in the On
position and the engine not running, depressing this
switch for about six seconds will display the engine
hours information. Holding this switch depressed
while turning the ignition switch from the Off posi-
tion to the On position will initiate the EMIC self-di-
agnostic actuator test. Refer to the appropriate
diagnostic information for additional details on this
VFD function. The EMIC microprocessor remembers
which display mode is active when the ignition
switch is turned to the Off position, and returns the
VFD display to that mode when the ignition switch is
turned On again.
The VFD units are diagnosed using the EMIC self-
diagnostic actuator test. (Refer to 8 - ELECTRICAL/
INSTRUMENT CLUSTER - DIAGNOSIS AND
TESTING). Proper testing of the PCI data bus and
the electronic data bus message inputs to the EMIC
that control some of the VFD functions requires the
use of a DRBIIItscan tool. Refer to the appropriate
diagnostic information. Specific operation details for
the odometer, the trip odometer, the gear selector
indicator and the various warning and reminder indi-
cator functions of the VFD may be found elsewhere
in this service information.
8J - 8 INSTRUMENT CLUSTERDR
INSTRUMENT CLUSTER (Continued)

ODOMETER
DESCRIPTION
An odometer and trip odometer are standard
equipment in all instrument clusters (Fig. 23). The
odometer, trip odometer, and engine hours informa-
tion are displayed in a common electronic, blue-green
Vacuum-Fluorescent Display (VFD). The VFD is sol-
dered onto the cluster electronic circuit board and is
visible through a window with a smoked clear lens
located on the lower edge of the tachometer gauge
dial face of the cluster overlay. The dark lens over
the VFD prevents it from being clearly visible when
it is not illuminated. However, the odometer, trip
odometer, and engine hours information are not dis-
played simultaneously. The trip odometer reset
switch on the instrument cluster circuit board toggles
the display between odometer and trip odometer
modes by depressing the odometer/trip odometer
switch button that extends through the lower edge of
the cluster lens, just left of the odometer VFD. When
the trip odometer information is displayed, the word
ªTRIPº is also illuminated in the upper right corner
of the VFD in a blue-green color and at the same
lighting level as the trip odometer information. The
engine hours information replaces the selected odom-
eter or trip odometer information whenever the igni-
tion switch is in the On position and the engine is
not running.
The odometer, trip odometer, and engine hours
information is stored in the instrument cluster mem-
ory. This information can be increased when the
proper inputs are provided to the instrument cluster,
but the information cannot be decreased. The odom-
eter can display values up to 999,999 kilometers
(999,999 miles). The odometer latches at these val-
ues, and will not roll over to zero. The trip odometer
can display values up to 9,999.9 kilometers (9,999.9
miles) before it rolls over to zero. The odometer dis-
play does not have a decimal point and will not show
values less than a full unit (kilometer or mile), while
the trip odometer display does have a decimal point
and will show tenths of a unit (kilometer or mile).
The unit of measure (kilometers or miles) for the
odometer and trip odometer display is not shown in
the VFD. The unit of measure for the instrument
cluster odometer/trip odometer is selected at the time
that it is manufactured, and cannot be changed.
Engine hours are displayed in the format, ªhr9999º.The cluster will accumulate values up to 9,999 hours
before the display rolls over to zero.
The odometer has a ªRental Carº mode, which will
illuminate the odometer information in the VFD
whenever the driver side front door is opened with
the ignition switch in the Off or Accessory positions.
During daylight hours (exterior lamps are Off) the
VFD is illuminated at full brightness for clear visibil-
ity. At night (exterior lamps are On) the VFD lighting
level is adjusted with the other cluster illumination
lamps using the panel lamps dimmer thumbwheel on
the headlamp switch. However, a ªParadeº mode
position of the panel lamps dimmer thumbwheel
allows the VFD to be illuminated at full brightness if
the exterior lamps are turned On during daylight
hours.
The VFD, the trip odometer switch, and the trip
odometer switch button are serviced as a unit with
the instrument cluster.
OPERATION
The odometer and trip odometer give an indication
to the vehicle operator of the distance the vehicle has
traveled. The engine hours give an indication of the
cumulative engine-on time. This indicator is con-
trolled by the instrument cluster circuitry based
upon cluster programming and electronic messages
received by the cluster from the Powertrain Control
Module (PCM) over the Programmable Communica-
tions Interface (PCI) data bus. The odometer, trip
odometer and engine hours information is displayed
by the instrument cluster Vacuum Fluorescent Dis-
play (VFD). The VFD will display the odometer infor-
mation whenever any door is opened with the
ignition switch in the Off or Accessory positions, and
will display the last previously selected odometer or
trip odometer information when the ignition switch is
turned to the On or Start positions. The instrument
cluster circuitry controls the VFD and provides the
following features:
²Odometer/Trip Odometer Display Toggling-
Actuating the trip odometer reset switch button
momentarily with the VFD illuminated will toggle
the display between the odometer and trip odometer
information. Each time the VFD is illuminated with
the ignition switch in the On or Start positions, the
display will automatically return to the last mode
previously selected (odometer or trip odometer).
²Engine Hours Display Toggling- When the
trip odometer reset switch button is pressed and held
for longer than about six seconds with the ignition
switch in the On position and the engine speed mes-
sage from the PCM is zero, the trip odometer infor-
mation will be momentarily displayed, then the
engine hours information will be displayed. The VFD
must be displaying the odometer information when
Fig. 23 Odometer Display
8J - 32 INSTRUMENT CLUSTERDR

(11) Before starting engine, operate accelerator
pedal to check for any binding.
SWITCH
DESCRIPTION
Two separate switch pods operate the speed control
system. The steering-wheel-mounted switches use
multiplexed circuits to provide inputs to the PCM (to
the ECM for diesel) for ON, OFF, RESUME, ACCEL-
ERATE, SET, DECEL and CANCEL modes. Refer to
the owner's manual for more information on speed
control switch functions and setting procedures.
The individual switches cannot be repaired. If one
switch fails, the entire switch module must be
replaced.
Depending on engine control computer (JTEC
having a 3± plug connector or NGC having a 4±
plug connector), 2 types of switches are used.
Both types of switches are internally and exter-
nally different. The switch used with the NGC
system has an attached pigtail lead. The switch
used with the JTEC system does not have an
attached pigtail lead.
OPERATION
When speed control is selected by depressing the
ON, OFF switch, the PCM(ECM for diesel)allows
a set speed to be stored in its RAM for speed control.
To store a set speed, depress the SET switch while
the vehicle is moving at a speed between approxi-
mately 35 and 85 mph. In order for the speed control
to engage, the brakes cannot be applied, nor can the
gear selector be indicating the transmission is in
Park or Neutral.
The speed control can be disengaged manually by:
²Stepping on the brake pedal
²Depressing the OFF switch
²Depressing the CANCEL switch.
The speed control can be disengaged also by any of
the following conditions:
²An indication of Park or Neutral (auto. trans.)
²The VSS signal increases at a rate of 10 mph
per second (indicates that the co-efficient of friction
between the road surface and tires is extremely low)
²Depressing the clutch pedal (manual trans.).
²Excessive engine rpm (indicates that the trans-
mission may be in a low gear)
²The VSS signal decreases at a rate of 10 mph
per second (indicates that the vehicle may have
decelerated at an extremely high rate)
²If the actual speed is not within 20 mph of the
set speed
Fig. 6 SPEED CONTROL SERVO LOCATION
1 - BATTERY TRAY
2 - MOUNTING LUGS
3 - SERVO
4 - ELEC. CONNEC.
5 - MOUNTING SCREWS (3)
6 - MOUNTING BRACKET
7 - VACUUM LINE
Fig. 7 SERVO CABLE CLIP REMOVE/INSTALL Ð
TYPICAL
1 - SERVO MOUNTING NUTS (2)
2 - SERVO
3 - CABLE RETAINING CLIP
4 - SERVO CABLE AND SLEEVE
DRSPEED CONTROL 8P - 7
SERVO (Continued)

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 H20.
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 even-
tually 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, indicatedby 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
and deteriorate engine performance, driveability and
fuel economy.
The catalyst monitor uses dual oxygen sensors
(O2S's) to monitor the efficiency of the converter. The
dual O2S's sensor strategy is based on the fact that
as a catalyst deteriorates, its oxygen storage capacity
and its efficiency are both reduced. By monitoring
the oxygen storage capacity of a catalyst, its effi-
ciency can be indirectly calculated. The upstream
DREMISSIONS CONTROL 25 - 3
EMISSIONS CONTROL (Continued)

MODULE - INSTALLATION, FRONT
CONTROL........................8W-97-6
MODULE - INSTALLATION, FRONT
CONTROL...........................8E-5
MODULE - INSTALLATION, FUEL PUMP . . . 14-12
MODULE - INSTALLATION, FUEL TANK....14-64
MODULE - INSTALLATION, HANDS FREE . . . 8T-2
MODULE - INSTALLATION, HEATED SEAT . . . 8E-7
MODULE - INSTALLATION, HEATED SEAT . 8G-15
MODULE - INSTALLATION, INTEGRATED
POWER..........................8W-97-4
MODULE - INSTALLATION, REMOTE
KEYLESS ENTRY......................8N-8
MODULE - INSTALLATION, SENTRY KEY
IMMOBILIZER.......................8E-15
MODULE - INSTALLATION, WIPER.......8R-23
MODULE - OPERATION, AIRBAG
CONTROL..........................8O-11
MODULE - OPERATION, DRIVER DOOR....8N-5
MODULE - OPERATION, FRONT
CONTROL........................8W-97-5
MODULE - OPERATION, FRONT
CONTROL...........................8E-5
MODULE - OPERATION, FUEL PUMP.....14-11
MODULE - OPERATION, FUEL TANK......14-63
MODULE - OPERATION, HEATED SEAT.....8E-6
MODULE - OPERATION, HEATED SEAT....8G-14
MODULE - OPERATION, INTEGRATED
POWER..........................8W-97-3
MODULE - OPERATION, REMOTE
KEYLESS ENTRY......................8N-7
MODULE - OPERATION, SENTRY KEY
IMMOBILIZER.......................8E-13
MODULE - OPERATION, TRANSFER CASE
CONTROL..........................8E-16
MODULE - OPERATION, TRANSMISSION
CONTROL..........................8E-20
MODULE - OPERATION, WIPER.........8R-23
MODULE - REMOVAL, AIRBAG CONTROL . 8O-12
MODULE - REMOVAL, DRIVER DOOR.....8N-7
MODULE - REMOVAL, ENGINE CONTROL . . . 8E-4
MODULE - REMOVAL, FRONT CONTROL . 8W-97-6
MODULE - REMOVAL, FRONT CONTROL . . . 8E-5
MODULE - REMOVAL, FUEL PUMP.......14-12
MODULE - REMOVAL, FUEL TANK.......14-63
MODULE - REMOVAL, HANDS FREE.......8T-2
MODULE - REMOVAL, HEATED SEAT......8E-7
MODULE - REMOVAL, HEATED SEAT.....8G-15
MODULE - REMOVAL, INTEGRATED
POWER..........................8W-97-3
MODULE - REMOVAL, REMOTE KEYLESS
ENTRY..............................8N-7
MODULE - REMOVAL, SENTRY KEY
IMMOBILIZER.......................8E-15
MODULE - REMOVAL, WIPER...........8R-23
MODULE / SWITCH OPERATING MODES,
STANDARD PROCEDURE -
CONFIGURING A NEW.................8Q-3
MODULE LAMP REPLACEMENT -
STANDARD PROCEDURE...............8M-3
MODULE LENS REPLACEMENT -
STANDARD PROCEDURE...............8M-3
MODULE (SKIM) - DESCRIPTION,
SENTRY KEY IMMOBILIZER.............8Q-1
MODULE (SKIM) - OPERATION, SENTRY
KEY IMMOBILIZER
....................8Q-2
MOLDING - INSTALLATION, FRONT
DOOR INNER BELT
...................23-93
MOLDING - INSTALLATION, FRONT
DOOR OUTER BELT
...................23-93
MOLDING - INSTALLATION, REAR DOOR
INNER BELT
.........................23-94
MOLDING - INSTALLATION, REAR DOOR
OUTER BELT
........................23-94
MOLDING - REMOVAL, FRONT DOOR
INNER BELT
.........................23-93
MOLDING - REMOVAL, FRONT DOOR
OUTER BELT
........................23-92
MOLDING - REMOVAL, REAR DOOR
INNER BELT
.........................23-94
MOLDING - REMOVAL, REAR DOOR
OUTER BELT
........................23-93
MOLDINGS - INSTALLATION, BODY SIDE
. . 23-36
MOLDINGS - REMOVAL, BODY SIDE
.....23-36
MONITORED SYSTEMS - DESCRIPTION
....25-2
MONITORS - DESCRIPTION,
COMPONENT
.........................25-4MOTOR - DESCRIPTION, ADJUSTABLE
PEDAL...............................5-6
MOTOR - DESCRIPTION, BLOWER.......24-28
MOTOR - DESCRIPTION, DOOR LOCK.....8N-4
MOTOR - DESCRIPTION, IDLE AIR
CONTROL..........................14-28
MOTOR - DESCRIPTION, LUMBAR.......8N-18
MOTOR - DESCRIPTION, SHIFT . . 21-511,21-541,
21-575
MOTOR - DIAGNOSIS AND TESTING,
BLOWER...........................24-28
MOTOR - DIAGNOSIS AND TESTING,
DOOR LOCK.........................8N-4
MOTOR - DIAGNOSIS AND TESTING,
LUMBAR...........................8N-18
MOTOR - DIAGNOSIS AND TESTING,
STARTER ...........................8F-32
MOTOR - INSTALLATION, ADJUSTABLE
PEDAL...............................5-7
MOTOR - INSTALLATION, BLOWER......24-31
MOTOR - INSTALLATION, IDLE AIR
CONTROL..........................14-29
MOTOR - INSTALLATION, SHIFT . 21-511,21-541,
21-575
MOTOR - INSTALLATION, STARTER......8F-34
MOTOR - OPERATION, BLOWER.........24-28
MOTOR - OPERATION, DOOR LOCK.......8N-4
MOTOR - OPERATION, IDLE AIR
CONTROL..........................14-28
MOTOR - OPERATION, LUMBAR........8N-18
MOTOR - OPERATION, SHIFT.....21-511,21-541,
21-575
MOTOR - REMOVAL, ADJUSTABLE
PEDAL...............................5-7
MOTOR - REMOVAL, BLOWER..........24-31
MOTOR - REMOVAL, IDLE AIR CONTROL . . 14-29
MOTOR - REMOVAL, SHIFT.....21-511,21-541,
21-575
MOTOR - REMOVAL, STARTER..........8F-33
MOTOR - REMOVAL, WINDOW..........8N-20
MOTOR RELAY - DESCRIPTION,
STARTER ...........................8F-35
MOTOR RELAY - INSTALLATION,
STARTER ...........................8F-37
MOTOR RELAY - OPERATION, STARTER . . . 8F-36
MOTOR RELAY - REMOVAL, STARTER....8F-37
MOTOR RESISTOR BLOCK -
DESCRIPTION, BLOWER...............24-18
MOTOR RESISTOR BLOCK - DIAGNOSIS
AND TESTING, BLOWER...............24-19
MOTOR RESISTOR BLOCK -
INSTALLATION, BLOWER..............24-19
MOTOR RESISTOR BLOCK - OPERATION,
BLOWER...........................24-18
MOTOR RESISTOR BLOCK - REMOVAL,
BLOWER...........................24-19
MOTOR SWITCH - DESCRIPTION,
BLOWER...........................24-20
MOTOR SWITCH - DIAGNOSIS AND
TESTING, BLOWER...................24-20
MOTOR SWITCH - OPERATION, BLOWER . . 24-20
MOUNT - INSTALLATION, DISC BRAKE
CALIPER ADAPTER....................5-22
MOUNT - INSTALLATION, FRONT . . . 9-147,9-218,
9-287,9-59
MOUNT - INSTALLATION, REAR
....9-149,9-220,
9-288,9-61
MOUNT - REMOVAL, FRONT
. 9-146,9-217,9-286,
9-58
MOUNT - REMOVAL, REAR
. . 9-149,9-220,9-288,
9-61
MOUNTED STOP LAMP - INSTALLATION,
CENTER HIGH
.......................8L-11
MOUNTED STOP LAMP - REMOVAL,
CENTER HIGH
.......................8L-11
MOUNTED STOP LAMP UNIT -
INSTALLATION, CENTER HIGH
..........8L-11
MOUNTED STOP LAMP UNIT -
REMOVAL, CENTER HIGH
..............8L-11
MOUNTING - STANDARD PROCEDURE,
MATCH
.............................22-3
MUFFLER - 5.9L DIESEL - INSTALLATION
. 11-10
MUFFLER - 5.9L DIESEL - REMOVAL
.....11-10
MUFFLER - INSTALLATION
..............11-9
MUFFLER - REMOVAL
..................11-9
MULTI-FUNCTION SWITCH - DIAGNOSIS
AND TESTING
.......................8L-18MULTI-FUNCTION SWITCH -
INSTALLATION.......................8L-19
MULTI-FUNCTION SWITCH - REMOVAL . . . 8L-19
NAME PLATES - INSTALLATION,
EXTERIOR..........................23-38
NAME PLATES - REMOVAL, EXTERIOR....23-38
NATURAL VAC LEAK DETECTION ASSY -
DESCRIPTION.......................25-23
NATURAL VAC LEAK DETECTION ASSY -
INSTALLATION.......................25-25
NATURAL VAC LEAK DETECTION ASSY -
OPERATION.........................25-23
NATURAL VAC LEAK DETECTION ASSY -
REMOVAL..........................25-24
NAVIGATION - INSTALLATION, ANTENNA . . . 8A-6
NAVIGATION - REMOVAL, ANTENNA......8A-6
NAVIGATION/TELECOMMUNICATION -
DESCRIPTION........................8T-1
NAVIGATION/TELECOMMUNICATION -
OPERATION..........................8T-1
NECK SEAL - DIAGNOSIS AND TESTING,
RADIATOR CAP-TO-FILLER..............7-58
NEW MODULE / SWITCH OPERATING
MODES, STANDARD PROCEDURE -
CONFIGURING A......................8Q-3
NIGHT MIRROR - DESCRIPTION,
AUTOMATIC DAY.....................8N-11
NIGHT MIRROR - DIAGNOSIS AND
TESTING, AUTOMATIC DAY.............8N-11
NIGHT MIRROR - OPERATION,
AUTOMATIC DAY.....................8N-11
NIGHT MIRROR - REMOVAL,
AUTOMATIC DAY......................8N-12
NOISE - DIAGNOSIS AND TESTING,
WIND...............................23-2
NOISE OR VIBRATION - DIAGNOSIS AND
TESTING, TIRE.......................22-7
NOISE SUPPRESSION GROUND STRAP -
DESCRIPTION, RADIO..................8A-9
NOISE SUPPRESSION GROUND STRAP -
INSTALLATION, RADIO................8A-10
NOISE SUPPRESSION GROUND STRAP -
OPERATION, RADIO...................8A-9
NOISE SUPPRESSION GROUND STRAP -
REMOVAL, RADIO.....................8A-9
NON-DEPLOYED SUPPLEMENTAL
RESTRAINTS - STANDARD
PROCEDURE, HANDLING...............8O-6
NON-MONITORED CIRCUITS -
OPERATION..........................25-8
NOZZLE - DESCRIPTION, WASHER......8R-11
NOZZLE - INSTALLATION, WASHER......8R-12
NOZZLE - OPERATION, WASHER........8R-12
NOZZLE - REMOVAL, WASHER..........8R-12
NUMBER - DESCRIPTION, VEHICLE
IDENTIFICATION....................Intro.-1
NV241 GENII - ASSEMBLY, TRANSFER
CASE.............................21-428
NV241 GENII - CLEANING, TRANSFER
CASE.............................21-426
NV241 GENII - DESCRIPTION, TRANSFER
CASE.............................21-415
NV241 GENII - DIAGNOSIS AND
TESTING, TRANSFER CASE............21-416
NV241 GENII - DISASSEMBLY,
TRANSFER CASE....................21-417
NV241 GENII - INSPECTION, TRANSFER
CASE.............................21-426
NV241 GENII - INSTALLATION,
TRANSFER CASE....................21-438
NV241 GENII - OPERATION, TRANSFER
CASE.............................21-415
NV241 GENII - REMOVAL, TRANSFER
CASE.............................21-417
NV241 GENII - TRANSFER CASE........21-438
NV241/NV243 - TRANSFER CASE.......21-439
NV243 - ASSEMBLY, TRANSFER CASE . . . 21-496
NV243 - CLEANING, TRANSFER CASE . . . 21-493
NV243 - DESCRIPTION, TRANSFER CASE . 21-482
NV243 - DIAGNOSIS AND TESTING,
TRANSFER CASE....................21-483
NV243 - DISASSEMBLY, TRANSFER
CASE
.............................21-484
NV243 - INSPECTION, TRANSFER CASE
. . 21-493
NV243 - INSTALLATION, TRANSFER
CASE
.............................21-505
NV243 - OPERATION, TRANSFER CASE
. . 21-483
NV243 - REMOVAL, TRANSFER CASE
....21-484
DRINDEX 21
Description Group-Page Description Group-Page Description Group-Page