length DODGE RAM 1500 1998 2.G Repair Manual

CARGO BOX - TIE DOWN
REMOVAL
(1) Remove the bolts and remove the tie down
cleat. (Fig. 4)
INSTALLATION
(1) Install the tie down cleat and install the bolts.
(2) Tighten the bolts to 34 N´m (25 ft. lbs.).
COWL GRILLE
REMOVAL
(1) Remove the wiper arms. (Refer to 8 - ELEC-
TRICAL/WIPERS/WASHERS/WIPER ARMS -
REMOVAL)
(2) Disconnect the washer hose.
(3) Remove the hood seal.
(4) Remove the six push pin fasteners from the
front of the grille. (Fig. 5)
(5) Remove the two rear corner screws and remove
the grilles.
INSTALLATION
(1) Install the grill and install the two rear corner
screws.
(2) Install the six push pin fasteners along the
front of the grille.
(3) Install the hood seal.
(4) Connect the washer hose.(5) Install the wiper arms. (Refer to 8 - ELECTRI-
CAL/WIPERS/WASHERS/WIPER ARMS - INSTAL-
LATION)
EXTERIOR NAME PLATES
REMOVAL
NOTE: Exterior name plates are attached to body
panels with adhesive tape.
(1) Apply a length of masking tape on the body,
parallel to the top edge and one end of the name
plate to use as a guide for installation, if necessary.
(2) If temperature is below 21ÉC (70ÉF) warm
emblem with a heat lamp or gun. Do not exceed 52ÉC
(120ÉF) when heating name plate.
(3) Using a trim stick C-4755 or equivalent,
remove and discard the name plate.
INSTALLATION
(1) Thoroughly clean all residue from the name
plate attachment area of the body panel.
(2) Wipe area with a clean lint free cloth moist-
ened with a 50% solution of water and alcohol and
wipe dry immediately with a dry lint free cloth.
(3) Remove protective cover from adhesive tape on
back of name plate.
(4)
Position name plate properly on the body panel.
(5) Apply consistent and uniform pressure over the
entire surface of the name plate, with palm of hand.
(6) If temperature is below 21ÉC (70ÉF) warm
emblem with a heat lamp or gun to assure adhesion.
Do not exceed 52ÉC (120ÉF) when heating name
plate.
Fig. 4 TIE DOWN CLEAT
1 - BOLTS (2)
2 - CLEAT
Fig. 5 COWL GRILLE
1 - PUSH PIN FASTENERS (6)
2 - COWL GRILLE
3 - SCREWS (2)
23 - 38 EXTERIORDR

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)