1998 DODGE RAM 1500 Body

that secure the mode door adapter to the front the
HVAC housing.
(6) Install the two screws that secure the mode
door adapter to the top of the HVAC housing.
Tighten the screws to 2.2 N´m (20 in. lbs.).
(7) Install the mode door actuator and sleeve to
the upper half of the HVAC housing (Refer to 24 -
HEATING & AIR CONDITIONING/CONTROLS/
MODE DOOR ACTUATOR - INSTALLATION).
(8) Install the instrument panel (Refer to 23 -
BODY/INSTRUMENT PANEL/INSTRUMENT
PANEL ASSEMBLY - INSTALLATION).
RECIRCULATION 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.
(1) Remove the HVAC housing from the vehicle
and place it on the workbench (Refer to 24 - HEAT-
ING & AIR CONDITIONING/DISTRIBUTION/HVAC
HOUSING - REMOVAL).
(2) Remove the recirculation door actuator from
the recirculation housing (Refer to 24 - HEATING &
AIR CONDITIONING/CONTROLS/RECIRCULA-
TION DOOR ACTUATOR - REMOVAL).
(3) Remove the two screws and disengage the two
plastic retaining tabs that secure the recirculation
housing to the HVAC housing (Fig. 14).
(4) Remove the recirculation housing from the
HVAC housing.
(5) Gently slide the recirculation door toward the
outside of the recirculation housing. Tilt and lift the
door out of the housing.
(6) Inspect the recirculation door, seals and the
HVAC recirculation housing for damage or binding
and repair or replace components as required.
Fig. 13 HVAC Mode Door
1 - MODE DOOR ADAPTER
2 - SPRING RETAINER
3 - SCREW (2)
4 - MODE DOOR ACTUATOR
5 - MODE DOOR
DRDISTRIBUTION 24 - 39
MODE DOOR (Continued)

STANDARD PROCEDURE - REFRIGERANT
SYSTEM SERVICE EQUIPMENT
WARNING: EYE PROTECTION MUST BE WORN
WHEN SERVICING AN AIR CONDITIONING REFRIG-
ERANT SYSTEM. TURN OFF (ROTATE CLOCKWISE)
ALL VALVES ON THE EQUIPMENT BEING USED
BEFORE CONNECTING TO, OR DISCONNECTING
FROM THE REFRIGERANT SYSTEM. FAILURE TO
OBSERVE THESE WARNINGS MAY RESULT IN PER-
SONAL INJURY.
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) and (Refer to 24 - HEATING & AIR CON-
DITIONING/PLUMBING - CAUTION).
When servicing the air conditioning system, a
R-134a refrigerant recovery/recycling/charging sta-
tion that meets SAE Standard J2210 must be used
(Fig. 2). Contact an automotive service equipment
supplier for refrigerant recovery/recycling/charging
equipment. Refer to the operating instructions sup-
plied by the equipment manufacturer for proper care
and use of this equipment.
A manifold gauge set may be needed with some
recovery/recycling/charging equipment (Fig. 3). The
service hoses on the gauge set being used should
have manual (turn wheel), or automatic back-flow
valves at the service port connector ends. This will
prevent refrigerant from being released into the
atmosphere.
MANIFOLD GAUGE SET CONNECTIONS
CAUTION: Do not use an R-12 manifold gauge set
on an R-134a system. The refrigerants are not com-
patible and system damage will result.
LOW PRESSURE GAUGE HOSE The low pressure
hose (Blue with Black stripe) attaches to the low side
service port. This service port is located on the suc-
tion line between the accumulator outlet port and the
A/C compressor.
HIGH PRESSURE GAUGE HOSE The high pres-
sure hose (Red with Black stripe) attaches to the
high side service port. This service port is located on
the discharge line near the A/C compressor. On this
model, an A/C pressure transducer is installed onto
the high pressure service port. A/C high side pres-
sures can be read using a DRBIIItscan tool. Refer to
Body Diagnostic Procedures.
RECOVERY/RECYCLING/EVACUATION/CHARG-
ING HOSE The center manifold hose (Yellow, or
White, with Black stripe) is used to recover, evacu-
ate, and charge the refrigerant system. When the low
or high pressure valves on the manifold gauge set
are opened, the refrigerant in the system will escape
through this hose.
Fig. 2 Refrigerant Recovery/Recycling Station -
Typical
1 - R-134a REFRIGERANT STATION
Fig. 3 MANIFOLD GAUGE SET - TYPICAL
1 - HIGH PRESSURE GAUGE
2 - VALVE
3 - VACUUM/REFRIGERANT HOSE (YELLOW W/ BLACK STRIPE)
4 - HIGH PRESSURE HOSE (RED W/ BLACK STRIPE)
5 - LOW PRESSURE HOSE (BLUE W/ BLACK STRIPE)
6 - VALVE
7 - LOW PRESSURE GAUGE
24 - 46 PLUMBINGDR
PLUMBING (Continued)

ING/PLUMBING - STANDARD PROCEDURE -
REFRIGERANT RECOVERY).
(5) Remove the plastic cover from the condenser
outlet stud.
(6) Remove the nut that secures the liquid line fit-
ting to the condenser outlet (Fig. 26).
(7) Disconnect the liquid line from the condenser.
(8) Remove the seal from the liquid line fitting and
discard.
(9) Install plugs in, or tape over the liquid line fit-
ting and condenser outlet port.
(10) Disengage the liquid lines from the body
retaining clips.
(11) Remove the secondary retaining clip from the
spring-lock coupler that secures the front section of
the liquid line to the rear section of the liquid line.
(12) Using the proper A/C line disconnect tool, dis-
connect the front section of the liquid line from the
rear section of the liquid line (Refer to 24 - HEAT-
ING & AIR CONDITIONING/PLUMBING/REFRIG-
ERANT LINE COUPLER - REMOVAL).
(13) Remove the O-ring seal from the liquid line
fitting and discard.
(14) Install plugs in, or tape over the opened front
liquid line fitting and rear liquid line tube.
(15) Remove the secondary retaining clip from the
spring-lock coupler that secures the liquid line to the
evaporator inlet tube.
(16) Using the proper A/C line disconnect tool, dis-
connect the liquid line from the evaporator inlet tube
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING/REFRIGERANT LINE COUPLER -
REMOVAL).
(17) Remove the O-ring seal from the liquid line
fitting and discard.
(18) Install plugs in, or tape over the opened liquid
line fitting and evaporator inlet tube.
(19) Remove both sections of the liquid line from
the engine compartment.
INSTALLATION
(1) Position both sections of the liquid line into the
engine compartment.
(2) Remove the tape or plugs from the rear liquid
line fitting and the evaporator inlet tube.
(3) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the rear liquid line
fitting. Use only the specified O-ring as it is made of
a special material for the R-134a system. Use only
refrigerant oil of the type recommended for the A/C
compressor in the vehicle.
(4) Connect the liquid line fitting to the evaporator
inlet tube (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING/REFRIGERANT LINE COU-
PLER - INSTALLATION).(5) Install the secondary retaining clip onto the
spring-lock coupler that secures the liquid line fitting
to the evaporator inlet tube.
(6) Remove the tape or plugs from the front liquid
line fitting and the rear liquid line tube.
(7) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the front liquid line
fitting. Use only the specified O-ring as it is made of
a special material for the R-134a system. Use only
refrigerant oil of the type recommended for the A/C
compressor in the vehicle.
(8) Connect the front liquid line fitting to the rear
liquid line tube (Refer to 24 - HEATING & AIR CON-
DITIONING/PLUMBING/REFRIGERANT LINE
COUPLER - INSTALLATION).
(9) Install the secondary retaining clip onto the
spring-lock coupler that secures the front liquid line
fitting to the rear liquid line tube.
(10) Engage the liquid lines to the body retaining
clips.
(11) Remove the tape or plugs from the liquid line
fitting and condenser outlet port.
(12) Lubricate a new rubber O-ring seal with clean
refrigerant oil and install it on the liquid line fitting.
Use only the specified O-ring as it is made of a spe-
Fig. 26 A/C Liquid Line - Typical
1 - BODY RETAINING CLIP
2 - SECONDARY RETAINING CLIP
3 - BODY RETAINING CLIP
4 - LIQUID LINE (REAR SECTION)
5 - SECONDARY RETAINING CLIP
6 - EVAPORATOR INLET TUBE
7 - A/C CONDENSER
8 - NUT
9 - BODY RETAINING CLIP
10 - LIQUID LINE (FRONT SECTION)
24 - 66 PLUMBINGDR
LIQUID LINE (Continued)

EXCESSIVE OIL CONSUMPTION
Although the PCM monitors engine exhaust oxygen
content when the system is in closed loop, it cannot
determine excessive oil consumption.
THROTTLE BODY AIR FLOW
The PCM cannot detect a clogged or restricted air
cleaner inlet or filter element.
VACUUM ASSIST
The PCM cannot detect leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices. However, these could cause the PCM
to store a MAP sensor diagnostic trouble code and
cause a high idle condition.PCM SYSTEM GROUND
The PCM cannot determine a poor system ground.
However, one or more diagnostic trouble codes may
be generated as a result of this condition. The mod-
ule should be mounted to the body at all times, also
during diagnostic.
PCM CONNECTOR ENGAGEMENT
The PCM may not be able to determine spread or
damaged connector pins. However, it might store
diagnostic trouble codes as a result of spread connec-
tor pins.
DREMISSIONS CONTROL 25 - 9
EMISSIONS CONTROL (Continued)

OPERATION
The main purpose of the LDP is to pressurize the
fuel system for leak checking. It closes the EVAP sys-
tem vent to atmospheric pressure so the system can
be pressurized for leak testing. The diaphragm is
powered by engine vacuum. It pumps air into the
EVAP system to develop a pressure of about 7.59
H2O (1/4) psi. A reed switch in the LDP allows the
PCM to monitor the position of the LDP diaphragm.
The PCM uses the reed switch input to monitor how
fast the LDP is pumping air into the EVAP system.
This allows detection of leaks and blockage. The LDP
assembly consists of several parts (Fig. 5). The sole-
noid is controlled by the PCM, and it connects theupper pump cavity to either engine vacuum or atmo-
spheric pressure. A vent valve closes the EVAP sys-
tem to atmosphere, sealing the system during leak
testing. The pump section of the LDP consists of a
diaphragm that moves up and down to bring air in
through the air filter and inlet check valve, and
pump it out through an outlet check valve into the
EVAP system. The diaphragm is pulled up by engine
vacuum, and pushed down by spring pressure, as the
LDP solenoid turns on and off. The LDP also has a
magnetic reed switch to signal diaphragm position to
the PCM. When the diaphragm is down, the switch is
closed, which sends a 12 V (system voltage) signal to
the PCM. When the diaphragm is up, the switch is
open, and there is no voltage sent to the PCM. This
allows the PCM to monitor LDP pumping action as it
turns the LDP solenoid on and off.
Fig. 4 TYPICAL SYSTEM COMPONENTS
1 - Throttle Body
2 - Service Vacuum Supply Tee (SVST)
3 - LDP Solenoid
4 - EVAP System Air Filter
5 - LDP Vent Valve
6 - EVAP Purge Orifice
7 - EVAP Purge Solenoid
8 - Service Port
9 - To Fuel Tank
10 - EVAP Canister
11 - LDP
12 - Intake Air Plenum
Fig. 5 EVAP LEAK DETECTION SYSTEM
COMPONENTS
1 - Reed Switch
2 - Solenoid
3 - Spring
4 - Pump Cavity
5 - Diaphragm
6 - Inlet Check Valve
7 - Vent Valve
8 - From Air Filter
9 - To Canister
10 - Outlet Check Valve
11 - Engine Vacuum
25 - 14 EVAPORATIVE EMISSIONSDR
LEAK DETECTION PUMP (Continued)

5.7L V-8
The 5.7L V-8 engine is equipped with a closed
crankcase ventilation system and a Positive Crank-
case Ventilation (PCV) valve.
This system consists of:
²a PCV valve mounted into the top of the intake
manifold, located to the right / rear of the throttle
body (Fig. 12). The PCV valve is sealed to the intake
manifold with 2 o-rings (Fig. 13).
²passages in the intake manifold.
²tubes and hoses to connect the system compo-
nents.
5.9L V-8
The 5.9L V-8 engine is equipped with a closed
crankcase ventilation system and a positive crank-
case ventilation (PCV) valve.
This system consists of a PCV valve mounted on
the cylinder head (valve) cover with a hose extending
from the valve to the intake manifold (Fig. 14).
Another hose connects the opposite cylinder head
(valve) cover to the air cleaner housing to provide a
source of clean air for the system. A separate crank-
case breather/filter is not used.
Fig. 11 CRANKCASE BREATHERS (2) - 3.7L V-6 /
4.7L V-8
1 - CRANKCASE BREATHERS (2)
2 - REAR OF ENGINE
Fig. 12 LOCATION 5.7L PCV VALVE
1 - TOP OF INTAKE MANIFOLD
2 - THROTTLE BODY
3 - AIR RESONATOR
4 - P C V VA LV E
Fig. 13 5.7L PCV VALVE
1 - P C V VA LV E
2 - O-RINGS
3 - ALIGNMENT TABS
25 - 18 EVAPORATIVE EMISSIONSDR
PCV VALVE (Continued)

OPERATION
The PCV system operates by engine intake mani-
fold vacuum (Fig. 15). Filtered air is routed into the
crankcase through the air cleaner hose. The metered
air, along with crankcase vapors, are drawn through
the PCV valve and into a passage in the intake man-
ifold. The PCV system manages crankcase pressure
and meters blow by gases to the intake system,
reducing engine sludge formation.The PCV valve contains a spring loaded plunger.
This plunger meters the amount of crankcase vapors
routed into the combustion chamber based on intake
manifold vacuum.
When the engine is not operating or during an
engine pop-back, the spring forces the plunger back
against the seat (Fig. 16). This will prevent vapors
from flowing through the valve.
During periods of high manifold vacuum, such as
idle or cruising speeds, vacuum is sufficient to com-
pletely compress spring. It will then pull the plunger
to the top of the valve (Fig. 17). In this position there
is minimal vapor flow through the valve.
During periods of moderate manifold vacuum, the
plunger is only pulled part way back from inlet. This
results in maximum vapor flow through the valve
(Fig. 18).
Fig. 14 PCV VALVE/HOSE - 5.9L V-8
1 - P C V VA LV E
2 - PCV VALVE HOSE CONNECTIONS
Fig. 15 TYPICAL CLOSED CRANKCASE
VENTILATION SYSTEM
1 - THROTTLE BODY
2 - AIR CLEANER
3 - AIR INTAKE
4 - P C V VA LV E
5 - COMBUSTION CHAMBER
6 - BLOW-BY GASES
7 - CRANKCASE BREATHER/FILTER
Fig. 16 ENGINE OFF OR ENGINE BACKFIRE - NO
VAPOR FLOW
Fig. 17 HIGH INTAKE MANIFOLD VACUUM -
MINIMAL VAPOR FLOW
Fig. 18 MODERATE INTAKE MANIFOLD VACUUM -
MAXIMUM VAPOR FLOW
DREVAPORATIVE EMISSIONS 25 - 19
PCV VALVE (Continued)

REMOVAL
3.7L V-6 / 4.7L V-8
The PCV valve is located on the oil filler tube (Fig.
22). Two locating tabs are located on the side of the
valve (Fig. 22). These 2 tabs fit into a cam lock in the
oil filler tube. An o-ring seals the valve to the filler
tube.
(1) Disconnect PCV line/hose (Fig. 22) by discon-
necting rubber hose at PCV valve fitting.
(2) Remove PCV valve at oil filler tube by rotating
PCV valve downward (counter-clockwise) until locat-
ing tabs have been freed at cam lock (Fig. 22). After
tabs have cleared, pull valve straight out from filler
tube.To prevent damage to PCV valve locating
tabs, valve must be pointed downward for
removal. Do not force valve from oil filler tube.
(3) After valve is removed, check condition of valve
o-ring (Fig. 22).
5.7L V-8
The PCV valve is mounted into the top of the
intake manifold, located to the right / rear of the
throttle body (Fig. 12). The PCV valve is sealed to
the intake manifold with 2 o-rings (Fig. 13).
(1) Remove PCV valve by rotating counter-clock-
wise 90 degrees until locating tabs have been freed.
After tabs have cleared, pull valve straight up from
intake manifold.(2) After valve is removed, check condition of 2
valve o-rings.
INSTALLATION
3.7L V6 / 4.7L V-8
The PCV valve is located on the oil filler tube. Two
locating tabs are located on the side of the valve.
These 2 tabs fit into a cam lock in the oil filler tube.
An o-ring seals the valve to the filler tube.
(1) Return PCV valve back to oil filler tube by
placing valve locating tabs into cam lock. Press PCV
valve in and rotate valve upward. A slight click will
be felt when tabs have engaged cam lock. Valve
should be pointed towards rear of vehicle.
(2) Connect PCV line/hose and rubber hose to PCV
valve.
Fig. 21 CHECK VALVES - PCV SYSTEM - 3.7L V-6 /
4.7L V-8
1 - CONNECTING HOSES
2 - CHECK VALVES
Fig. 22 PCV VALVE/OIL FILLER TUBE LOCATION -
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 - 21
PCV VALVE (Continued)