change time DODGE RAM 2001 Service Service Manual

is not required when a crankshaft and bearings are
replaced.
(1) Remove the oil pan and oil pickup tube (refer
to Oil Pan in this section for correct procedure).
(2) Remove the timing chain cover and gasket.
Remove and discard the front crankshaft oil seal and
cover gasket.
(3) Remove Transmission (refer to Group 21,
Transmission).
(4) Remove the rear seal retainer (refer to Crank-
shaft Rear Seal Retainer in this section for correct
procedure).
(5) Identify main bearing caps before removal (Fig.
30). Remove bearing caps and lower bearings one at
a time.
(6) Remove the connecting rod bearing caps.
(7) Lift the crankshaft straight out of the block.
(8) Remove the upper main bearings from the
block.
INSTALLATION
When a crankshaft is replaced, all main and con-
necting rod bearings should be replaced with new
bearings. Therefore, selective fitting of the bearings
is not required when a crankshaft and bearings are
replaced.NOTE: Lubricate crankshaft main bearings with
clean engine oil.
(1) Position upper main bearings into block.
(2) Position the crankshaft into the cylinder block.
(3) Lubricate the main journals with clean engine
oil. Install upper main bearings, caps and bolts. Fol-
low the 2 step tightening sequence, starting with
main bearing cap 1.
(4) Lubricate the connecting rod bearings and jour-
nals with clean engine oil. Carefully install connect-
ing rods to the crankshaft.
(5) Using Special Tool 8359 Seal Installer install
new oil into oil seal retainer.
(6) Using Special Tool 6687 Guide, install the rear
seal retainer with a new gasket.
(7) Install the timing chain cover with a new gas-
ket and oil seal.
(8) Prime oil pump by squirt oil in the oil filter
mounting hole and filling the J-trap of the front tim-
ing cover. When oil is running out, install oil filter
that has been filled with oil.
(9) Apply a rearward axial load of 667 N (150
lbs-f) on crankshaft centerline, driving No.3 main cap
and thrust bearing against No.3 bulkhead. Repeat
procedure, driving crankshaft forward to align rear
flange of thrust bearings in a common plane. Front
face of No.1 main cap must not extend forward in
front of face of No.1 bulkhead.
(10) Install the oil pickup tube. Tighten the bolts
to 16 N´m (144 in. lbs.) torque.
(11) Install the oil pan.
CRANKSHAFT MAIN
BEARINGS
STANDARD PROCEDUREÐMAIN BEARING
FITTING
Bearing caps are not interchangeable and should
be marked at removal to ensure correct assembly.
Upper and lower bearing halves are NOT inter-
changeable. All lower main bearing halves are inter-
changeable. Upper main bearing halves of No. 2, 4,
and 5 are interchangeable. Upper main bearing
halves of No. 1 and 6 are interchangeable, this also
applies to the lower bearing halves.
The No.3 main bearing is flanged to carry the
crankshaft thrust loads. This bearing is NOT inter-
changeable with any other bearing halves in the
engine. Bearing shells are available in standard and
the following undersizes: 0.25 mm (0.001 inch), 0.051
mm (0.002 inch), 0.076 mm (0.003 inch), 0.254 mm
(0.010 inch) and 0.305 mm (0.012 inch). Never install
an undersize bearing that will reduce clearance
below specifications.
Fig. 30 Main Bearing Identification
1 - MAIN BEARING CAP
2 - UPPER MAIN BEARINGS
3 - CRANKSHAFT
4 - LOWER MAIN BEARINGS
BR/BEENGINE 8.0L 9 - 203
CRANKSHAFT (Continued)

OIL
STANDARD PROCEDUREÐENGINE OIL
OIL LEVEL INDICATOR (DIPSTICK)
The engine oil level indicator is located at the right
front of the engine, left of the generator on 3.9L
engines (Fig. 53).
CRANKCASE OIL LEVEL INSPECTION
CAUTION: Do not overfill crankcase with engine oil,
oil foaming and oil pressure loss can result.
To ensure proper lubrication of an engine, the
engine oil must be maintained at an acceptable level.The acceptable levels are indicated between the ADD
and SAFE marks on the engine oil dipstick.
(1) Position vehicle on level surface.
(2) With engine OFF, allow approximately ten min-
utes for oil to settle to bottom of crankcase, remove
engine oil dipstick.
(3) Wipe dipstick clean.
(4) Install dipstick and verify it is seated in the
tube.
(5) Remove dipstick, with handle held above the
tip, take oil level reading.
(6) Add oil only if level is below the ADD mark on
dipstick.
ENGINE OIL CHANGE
Change engine oil at mileage and time intervals
described in the Maintenance Schedule. This infor-
mation can be found in the owner's manual.
TO CHANGE ENGINE OIL
Run engine until achieving normal operating tem-
perature.
(1) Position the vehicle on a level surface and turn
engine off.
(2) Hoist vehicle.
(3) Remove oil fill cap.
(4) Place a suitable drain pan under crankcase
drain.
(5) Remove drain plug from crankcase and allow
oil to drain into pan. Inspect drain plug threads for
stretching or other damage. Replace drain plug and
gasket if damaged.
(6) Install drain plug in crankcase.
(7) Change oil filter (Refer to 9 - ENGINE/LUBRI-
CATION/OIL FILTER - REMOVAL).
(8) Lower vehicle and fill crankcase with specified
type (Refer to LUBRICATION & MAINTENANCE/
FLUID TYPES - DESCRIPTION) and amount of
engine oil (Refer to LUBRICATION & MAINTE-
NANCE - SPECIFICATIONS).
1 - OIL TO MAIN OIL GALLERIES
2 - RELIEF VALVE
3 - OIL GALLERY FOR TAPPETS
4 - MAIN OIL GALLERY
5 - TAPPET OIL GALLERY
6 - HOLLOW PUSH ROD
7 - ROCKER ARM
8 - PLUG
9 - GASKET
10 - SPRING
11 - TIMING CHAIN COVER
12 - CAM BEARINGS
13 - HYDRAULIC TAPPET GALLERIES
14 - CAMSHAFT
15 - CRANKSHAFT
16 - OIL PASSAGE TO CONNECTING ROD JOURNALS17 - OIL PICKUP
18 - CONNECTING ROD JOURNALS
19 - CRANKSHAFT BEARINGS
20 - MAIN OIL GALLERY
21 - CRANKSHAFT
22 - OIL PICKUP TUBE
23 - CONNECT ROD JOURNALS
24 - CAMSHAFT BEARINGS
25 - TAPPET OIL GALLERY
26 - OIL FROM PICKUP TUBE
27 - CAMSHAFT
28 - TAPPET
29 - VALVE
30 - OIL PUMP RELIEF VALVE
Fig. 53 Oil Level Indicator Location
1 - CYLINDER HEAD COVER
2 - ENGINE OIL FILL CAP
3 - DIPSTICK
4 - ENGINE OIL FILTER
5 - FILTER BOSS
BR/BEENGINE 8.0L 9 - 217
LUBRICATION (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
4. Turbocharger noise. 4. Check turbocharger impeller and turbine
wheel for housing contact. Repair/replace
as required.
5. Gear train noise. 5. Visually inspect and measure gear
backlash. Replace gears as required.
6. Power function knock. 6. Check/replace rod and main bearings.
DIAGNOSIS AND TESTINGÐSMOKE
DIAGNOSIS CHARTS
The following charts include possible causes and
corrections forexcess or abnormalexhaust smoke.Small amounts of exhaust smoke (at certain times)
are to be considered normal for a diesel powered
engine.
EXCESSIVE BLACK SMOKE
POSSIBLE CAUSE CORRECTION
Air filter dirty or plugged. Check Filter MinderTat air filter (Refer to 9 - ENGINE/
AIR INTAKE SYSTEM/AIR CLEANER ELEMENT -
REMOVAL).
Air intake system restricted. Check entire air intake system including all hoses and
tubes for restrictions, collapsed parts or damage.
Repair/replace as necessary.
Air Leak in Intake System. Check entire air intake system including all hoses and
tubes for cracks, loose clamps and/or holes in rubber
ducts. Also check intake manifold for loose mounting
hardware.
Diagnostic Trouble Codes (DTC's) active or multiple,
intermittent DTC's.Refer to Powertrain Diagnostic Procedures Information.
Engine Control Module (ECM) not calibrated or ECM
has incorrect calibration.Refer to Powertrain Diagnostic Procedures Information.
Exhaust system restriction is above specifications. Check exhaust pipes for damage/restrictions. Repair as
necessary.
Fuel grade is not correct or fuel quality is poor. Temporarily change fuel brands and note condition.
Change brand if necessary.
Fuel injection pump malfunctioning. A DTC should have been set. If so, refer to Powertrain
Diagnostic Procedures Information.
Fuel injector malfunctioning. A DTC should have been set. Perform9Cylinder
Balance Test9using DRB scan tool to isolate individual
cylinders. Also refer to Powertrain Diagnostic
Procedures Information and, to (Refer to 14 - FUEL
SYSTEM/FUEL INJECTION/FUEL INJECTOR -
DIAGNOSIS AND TESTING).
Fuel return system restricted. Check fuel return line by checking overflow valve
(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY -
DIAGNOSIS AND TESTING).
Intake manifold restricted. Remove restriction.
Manifold Air Pressure (Boost) Sensor or sensor circuit
malfunctioning.A DTC should have been set. Refer to Powertrain
Diagnostic Procedures Information.
9 - 234 ENGINE 5.9L DIESELBR/BE
ENGINE 5.9L DIESEL (Continued)

(23) Connect the transmission quick-connect oil
cooler lines to the radiator. Push together until an
audible ªclickº is heard. Verify connection by pulling
apart.
(24) Raise vehicle.
(25) Connect a/c compressor suction/discharge hose
(if a/c equipped).
(26) Install the radiator lower hose and clamps.
(27) Install the starter motor (Refer to 8 - ELEC-
TRICAL/STARTING/STARTER MOTOR - INSTAL-
LATION).
(28) Install the transmission and transfer case (if
equipped).
(29) Connect the exhaust pipe to the turbocharger
elbow (Fig. 3). Torque the bolts to 34 N´m (25 ft. lbs.)
torque.
(30) Connect the transmission auxiliary oil cooler
lines (if equipped).
(31) Lower the vehicle
(32) Connect the heater core supply and return
hoses.
(33) Install the cooling fan and shroud at the same
time (Refer to 7 - COOLING/ENGINE/RADIATOR
FAN - INSTALLATION).
(34) Install the coolant recovery bottle to the fan
shroud (Fig. 2) and connect the hose to the radiator
filler neck.
(35) Install the windshield washer bottle to the fan
shroud and connect the pump supply hose and elec-
trical connections.
(36) Install the radiator upper hose and clamps.
(37) Change oil filter and install new engine oil.
(38) Fill cooling system with coolant (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(39) Connect battery negative cables.
(40) Perform the fuel line air bleed procedure
(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY -
STANDARD PROCEDURE).
(41) Start engine and inspect for engine oil, cool-
ant, and fuel leaks.
INSTALLATIONÐCRANKCASE BREATHER
VAPOR CANISTER
(1) Position vapor canister with strap over stud on
engine front cover. Install retaining nut. Tighten nut
10 N´m ( 89 in. lbs.).
(2) If removed, position hose onto crankcase
breather, then position clamp.
(3) Position lower portion of hose into vapor canis-
ter, then install and tighten cap.
SPECIFICATIONS
5.9L DIESEL
DESCRIPTION SPECIFICATION
Engine Type In-Line 6 Cyl. Turbo
Diesel
Bore and Stroke 102.0 X 120.0 mm
(4.02 X 4.72 in.)
Displacement 5.9L (359 cu. in.)
Compression Ratio
245 H.P. Version 17.0:1
235 H.P. Version 16.3:1
Horsepower (A/T and 5
Speed M/T)235 @ 2700 rpm
Horsepower (6 Speed M/T
Only)245 @ 2700 rpm
Torque Rating (A/T and 5
Speed M/T)460 ft. lbs. @ 1600 rpm
Torque Rating (6 Speed
M/T Only)505 ft. lbs. @ 1600 rpm
Firing Order 1-5-3-6-2-4
Lubrication System Pressure Feed-Full Flow
With Bypass Valve
Cylinder Block Cast Iron
Crankshaft Induction Hardened
Forged Steel
Cylinder Head Cast Iron With Valve
Seat Inserts
Combustion Chambers High Swirl Bowl
Camshaft Chilled Ductile Iron
Pistons Cast Aluminum
Connecting Rods Cross Rolled Micro Alloy
PISTONS AND CONNECTING RODS
Piston
Skirt Diameter 101.864 ± 101.88 mm
(4.0104 ± 4.011 in.)
Ring Groove Clearance
Intermediate (Max.) 0.095 mm (0.0037 in.)
Oil Control (Max.) 0.085 mm (0.0033 in.)
Piston Pins
Pin Diameter (Min.) 39.990 mm (1.5744 in.)
Bore Diameter (Max.) 40.025 mm (1.5758 in.)
Piston Ring End Gap
Top Ring 0.35 ± 0.45 mm
9 - 242 ENGINE 5.9L DIESELBR/BE
ENGINE 5.9L DIESEL (Continued)

LUBRICATION
DESCRIPTION
NOTE: Refer to (Fig. 148) and (Fig. 149) for circuit
illustrations.
A gear driven gerotor type oil pump is mounted
behind the front gear cover in the lower right portion
on the engine.
OPERATION
A gerotor style oil pump draws oil from the crank-
case through the suction tube and delivers it through
the block where it enters the oil cooler cover and
pressure regulator valve. When oil pressure exceeds
449 kPa (65 PSI), the valve opens exposing the dump
port, which routes excess oil back to the oil sump.
At the same time, oil is directed to a cast in pas-
sage in the oil cooler cover, leading to the oil cooler
element. As the oil travels through the element
plates, it is cooled by engine coolant traveling past
the outside of the plates. It is then routed to the oil
filter head and through a full flow oil filter. If a
plugged filter is encountered, the filter by-pass valve
opens, allowing unfiltered oil to lubricate the engine.
This condition can be avoided by frequent oil and fil-
ter changes, per the maintenance schedules found in
the owners manual. The by-pass valve is calibrated
to open when it sees a pressure drop of more than
344 kPa (50 psi) across the oil filter.The oil filter head then divides the oil between the
engine and the turbocharger. The turbocharger
receives filtered, cooled and pressurized oil through a
supply line from the filter head. The oil lubricates
the turbocharger and returns to the pan by way of a
drain tube connecting the bottom of the turbocharger
to a pressed in tube in the cylinder block.
Oil is then carried across the block to an angle
drilling which intersects the main oil rifle. The main
oil rifle runs the length of the block and delivers oil
to the crankshaft main journals and valve train. Oil
travels to the crankshaft through a series of transfer
drillings (one for each main bearing) and lubricates a
groove in the main bearing upper shell. From there
another drilling feeds the camshaft main journals.
The piston cooling nozzles are also supplied by the
main bearing upper shell. Crankshaft internal cross-
drillings supply oil to the connecting rod journals.
Another series of transfer drillings intersecting the
main oil rifle supply the valve train components. Oil
travels up the drilling, through a hole in the head
gasket, and through a drilling in the cylinder head
(one per cylinder), where it enters the rocker arm
pedestal and is divided between the intake and
exhaust rocker arm. Oil travels up and around the
rocker arm mounting bolt, and lubricates the rocker
shaft by cross drillings that intersect the mounting
bolt hole. Grooves at both ends of the rocker shaft
supply oil through the rocker arm where the oil trav-
els to the push rod and socket balls (Fig. 148) and
(Fig. 149).
9 - 292 ENGINE 5.9L DIESELBR/BE

(1) Be sure fuel tank contains fuel before starting
test. If tank is empty or near empty, amperage read-
ings will be incorrect.
(2) Obtain LCS adapter.
(3) Plug cable from LCS adapter into DRB scan
tool at SET 1 receptacle.
(4) Plug DRB into vehicle 16±way connector (data
link connector).
(5) Connect (-) and (+) test cable leads into LCS
adapter receptacles. Use10 amp (10A +)receptacle
and common (-) receptacles.
(6) Gain access to MAIN MENU on DRB screen.
(7) Press DVOM button on DRB.
(8) Using left/right arrow keys, highlight CHAN-
NEL 1 function on DRB screen.
(9) Press ENTER three times.
(10) Using up/down arrow keys, highlight RANGE
on DRB screen (screen will default to 2 amp scale).
(11) Press ENTER to change 2 amp scale to 10
amp scale.This step must be done to prevent
damage to DRB scan tool or LCS adapter
(blown fuse).
(12) Remove cover from Power Distribution Center
(PDC).
(13) Remove fuel pump relay from PDC. Refer to
label on PDC cover for relay location.
WARNING: BEFORE PROCEEDING TO NEXT STEP,
NOTE THE FUEL PUMP WILL BE ACTIVATED AND
SYSTEM PRESSURE WILL BE PRESENT. THIS WILL
OCCUR AFTER CONNECTING TEST LEADS FROM
LCS ADAPTER INTO FUEL PUMP RELAY CAVITIES.
THE FUEL PUMP WILL OPERATE EVEN WITH IGNI-
TION KEY IN OFF POSITION. BEFORE ATTACHING
TEST LEADS, BE SURE ALL FUEL LINES AND
FUEL SYSTEM COMPONENTS ARE CONNECTED.
CAUTION: To prevent possible damage to the vehi-
cle electrical system and LCS adapter, the test
leads must be connected into relay cavities exactly
as shown in following steps.
Depending upon vehicle model, year or engine con-
figuration, three different types of relays may be
used: Type-1, type-2 and type±3.
(14) If equipped withtype±1 relay(Fig. 13),
attach test leads from LCS adapter into PDC relay
cavities number 30 and 87. For location of these cav-
ities, refer to numbers stamped to bottom of relay
(Fig. 13).
(15) If equipped withtype±2 relay(Fig. 14),
attach test leads from LCS adapter into PDC relay
cavities number 30 and 87. For location of these cav-
ities, refer to numbers stamped to bottom of relay
(Fig. 14).(16) If equipped withtype±3 relay(Fig. 15),
attach test leads from LCS adapter into PDC relay
cavities number 3 and 5. For location of these cavi-
ties, refer to numbers stamped to bottom of relay
(Fig. 15).
Fig. 13 FUEL PUMP RELAY - TYPE 1
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
Fig. 14 FUEL PUMP RELAY - TYPE 2
TERMINAL LEGEND
NUMBER IDENTIFICATION
30 COMMON FEED
85 COIL GROUND
86 COIL BATTERY
87 NORMALLY OPEN
87A NORMALLY CLOSED
BR/BEFUEL DELIVERY - GASOLINE 14 - 11
FUEL PUMP (Continued)

(5) Install new plastic tie strap (Fig. 28) to secure
sensor pigtail harness to side of engine block. Thread
tie strap through casting hole on cylinder block.
FUEL PUMP RELAY
DESCRIPTION
The 5±pin, 12±volt, fuel pump relay is located in
the Power Distribution Center (PDC). Refer to the
label on the PDC cover for relay location.
OPERATION
The Powertrain Control Module (PCM) energizes
the electric fuel pump through the fuel pump relay.
The fuel pump relay is energized by first applying
battery voltage to it when the ignition key is turned
ON, and then applying a ground signal to the relay
from the PCM.
Whenever the ignition key is turned ON, the elec-
tric fuel pump will operate. But, the PCM will shut-
down the ground circuit to the fuel pump relay in
approximately 1±3 seconds unless the engine is oper-
ating or the starter motor is engaged.
REMOVAL
The fuel pump relay is located in the Power Distri-
bution Center (PDC) (Fig. 31). Refer to label on PDC
cover for relay location.
(1) Remove PDC cover.
(2) Remove relay from PDC.
(3) Check condition of relay terminals and PDC
connector terminals for damage or corrosion. Repair
if necessary before installing relay.
(4) Check for pin height (pin height should be the
same for all terminals within the PDC connector).
Repair if necessary before installing relay.
INSTALLATION
The fuel pump relay is located in the Power Distri-
bution Center (PDC) (Fig. 31). Refer to label on PDC
cover for relay location.
(1) Install relay to PDC.
(2) Install cover to PDC.
IDLE AIR CONTROL MOTOR
DESCRIPTION
The IAC stepper motor is mounted to the throttle
body, and regulates the amount of air bypassing the
control of the throttle plate. As engine loads and
ambient temperatures change, engine rpm changes.
A pintle on the IAC stepper motor protrudes into a
passage in the throttle body, controlling air flow
through the passage. The IAC is controlled by the
Powertrain Control Module (PCM) to maintain the
target engine idle speed.
OPERATION
At idle, engine speed can be increased by retract-
ing the IAC motor pintle and allowing more air to
pass through the port, or it can be decreased by
restricting the passage with the pintle and diminish-
ing the amount of air bypassing the throttle plate.
The IAC is called a stepper motor because it is
moved (rotated) in steps, or increments. Opening the
IAC opens an air passage around the throttle blade
which increases RPM.
The PCM uses the IAC motor to control idle speed
(along with timing) and to reach a desired MAP dur-
ing decel (keep engine from stalling).
The IAC motor has 4 wires with 4 circuits. Two of
the wires are for 12 volts and ground to supply electri-
cal current to the motor windings to operate the step-
per motor in one direction. The other 2 wires are also
for 12 volts and ground to supply electrical current to
operate the stepper motor in the opposite direction.
To make the IAC go in the opposite direction, the
PCM just reverses polarity on both windings. If only
1 wire is open, the IAC can only be moved 1 step
(increment) in either direction. To keep the IAC
motor in position when no movement is needed, the
PCM will energize both windings at the same time.
This locks the IAC motor in place.
In the IAC motor system, the PCM will count
every step that the motor is moved. This allows the
PCM to determine the motor pintle position. If the
memory is cleared, the PCM no longer knows the
position of the pintle. So at the first key ON, the
PCM drives the IAC motor closed, regardless of
where it was before. This zeros the counter. From
this point the PCM will back out the IAC motor and
keep track of its position again.
Fig. 31 Power Distribution Center (PDC)
1 - POWER DISTRIBUTION CENTER (PDC)
BR/BEFUEL INJECTION - GASOLINE 14 - 41
CRANKSHAFT POSITION SENSOR (Continued)

When engine rpm is above idle speed, the IAC is
used for the following:
²Off-idle dashpot (throttle blade will close quickly
but idle speed will not stop quickly)
²Deceleration air flow control
²A/C compressor load control (also opens the pas-
sage slightly before the compressor is engaged so
that the engine rpm does not dip down when the
compressor engages)
²Power steering load control
The PCM can control polarity of the circuit to con-
trol direction of the stepper motor.
IAC Stepper Motor Program:The PCM is also
equipped with a memory program that records the
number of steps the IAC stepper motor most recently
advanced to during a certain set of parameters. For
example: The PCM was attempting to maintain a
1000 rpm target during a cold start-up cycle. The last
recorded number of steps for that may have been
125. That value would be recorded in the memory
cell so that the next time the PCM recognizes the
identical conditions, the PCM recalls that 125 steps
were required to maintain the target. This program
allows for greater customer satisfaction due to
greater control of engine idle.
Another function of the memory program, which
occurs when the power steering switch (if equipped),
or the A/C request circuit, requires that the IAC step-
per motor control engine rpm, is the recording of the
last targeted steps into the memory cell. The PCM
can anticipate A/C compressor loads. This is accom-
plished by delaying compressor operation for approx-
imately 0.5 seconds until the PCM moves the IAC
stepper motor to the recorded steps that were loaded
into the memory cell. Using this program helps elim-
inate idle-quality changes as loads change. Finally,
the PCM incorporates a9No-Load9engine speed lim-
iter of approximately 1800 - 2000 rpm, when it rec-
ognizes that the TPS is indicating an idle signal and
IAC motor cannot maintain engine idle.
A (factory adjusted) set screw is used to mechani-
cally limit the position of the throttle body throttle
plate.Never attempt to adjust the engine idle
speed using this screw.All idle speed functions are
controlled by the IAC motor through the PCM.
REMOVAL - 3.9L/5.2L/5.9L
The IAC motor is located on the back of the throt-
tle body (Fig. 32).
(1) Remove air cleaner assembly.
(2) Disconnect electrical connector from IAC motor.
(3) Remove two mounting bolts (screws) (Fig. 32).
(4) Remove IAC motor from throttle body.
REMOVAL - 8.0L
The IAC motor is located on the back of the throt-
tle body (Fig. 33).
(1) Remove the air cleaner cover.
(2) Remove the 4 air cleaner housing mounting
nuts and remove housing from throttle body.
(3) Disconnect electrical connector from IAC motor.
(4) Remove two mounting bolts (screw).
(5) Remove IAC motor from throttle body.
INSTALLATION - 3.9L/5.2L/5.9L
The IAC motor is located on the back of the throt-
tle body (Fig. 32).
Fig. 32 Mounting Bolts (Screws)ÐIAC MotorÐ3.9L/
5.2L/5.9L Engines
1 - MOUNTING SCREWS
2 - IDLE SPEED MOTOR
Fig. 33 IAC MotorÐ8.0L Engine
1 - IDLE AIR CONTROL MOTOR
2 - INTAKE MANIFOLD (UPPER HALF)
3 - THROTTLE POSITION SENSOR
4 - THROTTLE BODY
14 - 42 FUEL INJECTION - GASOLINEBR/BE
IDLE AIR CONTROL MOTOR (Continued)

(1) Install sensor to intake manifold. Tighten to
12±15 N´m (110±130 in. lbs.) torque.
(2) Install electrical connector.
(3) Install air cleaner.
INSTALLATION - 8.0L
The intake manifold air temperature sensor is
located in the side of the intake manifold near the
front of throttle body (Fig. 35).
(1) Install sensor to intake manifold. Tighten to
12±15 N´m (110±130 in. lbs.) torque.
(2) Install electrical connector.
MANIFOLD ABSOLUTE
PRESSURE SENSOR
DESCRIPTION - 3.9L/5.2L/5.9L/8.0L
On 3.9L/5.2L/5.9L engines, the MAP sensor is
mounted on the side of the engine throttle body. The
sensor is connected to the throttle body with a rubber
L-shaped fitting.
On the 8.0L 10±cylinder engine, the MAP sensor is
mounted into the right side of the intake manifold.
OPERATION - 3.9L/5.2L/5.9L/8.0L
The MAP sensor is used as an input to the Power-
train Control Module (PCM). It contains a silicon
based sensing unit to provide data on the manifold
vacuum that draws the air/fuel mixture into the com-
bustion chamber. The PCM requires this information
to determine injector pulse width and spark advance.
When manifold absolute pressure (MAP) equals
Barometric pressure, the pulse width will be at max-
imum.
A 5 volt reference is supplied from the PCM and
returns a voltage signal to the PCM that reflects
manifold pressure. The zero pressure reading is 0.5V
and full scale is 4.5V. For a pressure swing of 0±15
psi, the voltage changes 4.0V. To operate the sensor,
it is supplied a regulated 4.8 to 5.1 volts. Ground is
provided through the low-noise, sensor return circuit
at the PCM.
The MAP sensor input is the number one contrib-
utor to fuel injector pulse width. The most important
function of the MAP sensor is to determine baromet-
ric pressure. The PCM needs to know if the vehicle is
at sea level or at a higher altitude, because the air
density changes with altitude. It will also help to cor-
rect for varying barometric pressure. Barometric
pressure and altitude have a direct inverse correla-
tion; as altitude goes up, barometric goes down. At
key-on, the PCM powers up and looks at MAP volt-
age, and based upon the voltage it sees, it knows the
current barometric pressure (relative to altitude).
Once the engine starts, the PCM looks at the voltageagain, continuously every 12 milliseconds, and com-
pares the current voltage to what it was at key-on.
The difference between current voltage and what it
was at key-on, is manifold vacuum.
During key-on (engine not running) the sensor
reads (updates) barometric pressure. A normal range
can be obtained by monitoring a known good sensor.
As the altitude increases, the air becomes thinner
(less oxygen). If a vehicle is started and driven to a
very different altitude than where it was at key-on,
the barometric pressure needs to be updated. Any
time the PCM sees Wide Open Throttle (WOT), based
upon Throttle Position Sensor (TPS) angle and RPM,
it will update barometric pressure in the MAP mem-
ory cell. With periodic updates, the PCM can make
its calculations more effectively.
The PCM uses the MAP sensor input to aid in cal-
culating the following:
²Manifold pressure
²Barometric pressure
²Engine load
²Injector pulse-width
²Spark-advance programs
²Shift-point strategies (certain automatic trans-
missions only)
²Idle speed
²Decel fuel shutoff
The MAP sensor signal is provided from a single
piezoresistive element located in the center of a dia-
phragm. The element and diaphragm are both made
of silicone. As manifold pressure changes, the dia-
phragm moves causing the element to deflect, which
stresses the silicone. When silicone is exposed to
stress, its resistance changes. As manifold vacuum
increases, the MAP sensor input voltage decreases
proportionally. The sensor also contains electronics
that condition the signal and provide temperature
compensation.
The PCM recognizes a decrease in manifold pres-
sure by monitoring a decrease in voltage from the
reading stored in the barometric pressure memory
cell. The MAP sensor is a linear sensor; meaning as
pressure changes, voltage changes proportionately.
The range of voltage output from the sensor is usu-
ally between 4.6 volts at sea level to as low as 0.3
volts at 26 in. of Hg. Barometric pressure is the pres-
sure exerted by the atmosphere upon an object. At
sea level on a standard day, no storm, barometric
pressure is approximately 29.92 in Hg. For every 100
feet of altitude, barometric pressure drops .10 in. Hg.
If a storm goes through it can change barometric
pressure from what should be present for that alti-
tude. You should know what the average pressure
and corresponding barometric pressure is for your
area.
14 - 44 FUEL INJECTION - GASOLINEBR/BE
INTAKE AIR TEMPERATURE SENSOR (Continued)

(3) Install MAP sensor mounting bolts (screws).
Tighten screws to 3 N´m (25 in. lbs.) torque.
(4) Install air cleaner.
INSTALLATION - 8.0L
The MAP sensor is mounted into the right upper
side of the intake manifold (Fig. 38). A rubber gasket
is used to seal the sensor to the intake manifold. The
rubber gasket is part of the sensor and is not ser-
viced separately.
(1) Check the condition of the sensor seal. Clean
the sensor and lubricate the rubber gasket with clean
engine oil.
(2) Clean the sensor opening in the intake mani-
fold.
(3) Install the sensor into the intake manifold.
(4) Install sensor mounting bolts. Tighten bolts to
2 N´m (20 in. lbs.) torque.
(5) Install the electrical connector to sensor.
O2 SENSOR
DESCRIPTION
The Oxygen Sensors (O2S) are attached to, and
protrude into the vehicle exhaust system. Depending
on the emission package, the vehicle may use a total
of either 2 or 4 sensors.
3.9L/5.2L/Light Duty 5.9L Engine:Four sensors
are used: 2 upstream (referred to as 1/1 and 2/1) and
2 downstream (referred to as 1/2 and 2/2). With this
emission package, the right upstream sensor (2/1) is
located in the right exhaust downpipe just before the
mini-catalytic convertor. The left upstream sensor
(1/1) is located in the left exhaust downpipe just
before the mini-catalytic convertor. The right down-
stream sensor (2/2) is located in the right exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor. The left down-
stream sensor (1/2) is located in the left exhaust
downpipe just after the mini-catalytic convertor, and
before the main catalytic convertor.
Medium and Heavy Duty 8.0L V-10 Engine:
Four sensors are used (2 upstream, 1 pre-catalyst
and 1 post-catalyst). With this emission package, the
1/1 upstream sensor (left side) is located in the left
exhaust downpipe before both the pre-catalyst sensor
(1/2), and the main catalytic convertor. The 2/1
upstream sensor (right side) is located in the right
exhaust downpipe before both the pre-catalyst sensor
(1/2), and the main catalytic convertor. The pre-cata-
lyst sensor (1/2) is located after the 1/1 and 2/1 sen-
sors, and just before the main catalytic convertor.
The post-catalyst sensor (1/3) is located just after the
main catalytic convertor.Heavy Duty 5.9L Engine:Two sensors are used.
They arebothreferred to as upstream sensors (left
side is referred to as 1/1 and right side is referred to
as 2/1). With this emission package, a sensor is
located in each of the exhaust downpipes before the
main catalytic convertor.
OPERATION
An O2 sensor is a galvanic battery that provides
the PCM with a voltage signal (0-1 volt) inversely
proportional to the amount of oxygen in the exhaust.
In other words, if the oxygen content is low, the volt-
age output is high; if the oxygen content is high the
output voltage is low. The PCM uses this information
to adjust injector pulse-width to achieve the
14.7±to±1 air/fuel ratio necessary for proper engine
operation and to control emissions.
The O2 sensor must have a source of oxygen from
outside of the exhaust stream for comparison. Cur-
rent O2 sensors receive their fresh oxygen (outside
air) supply through the wire harness. This is why it
is important to never solder an O2 sensor connector,
or pack the connector with grease.
Four wires (circuits) are used on each O2 sensor: a
12±volt feed circuit for the sensor heating element; a
ground circuit for the heater element; a low-noise
sensor return circuit to the PCM, and an input cir-
cuit from the sensor back to the PCM to detect sen-
sor operation.
Oxygen Sensor Heaters/Heater Relays:
Depending on the emissions package, the heating ele-
ments within the sensors will be supplied voltage
from either the ASD relay, or 2 separate oxygen sen-
sor relays. Refer to 8, Wiring Diagrams to determine
which relays are used.
The O2 sensor uses a Positive Thermal Co-efficient
(PTC) heater element. As temperature increases,
resistance increases. At ambient temperatures
around 70ÉF, the resistance of the heating element is
approximately 4.5 ohms. As the sensor's temperature
increases, resistance in the heater element increases.
This allows the heater to maintain the optimum
operating temperature of approximately 930É-1100ÉF
(500É-600É C). Although the sensors operate the
same, there are physical differences, due to the envi-
ronment that they operate in, that keep them from
being interchangeable.
Maintaining correct sensor temperature at all times
allows the system to enter into closed loop operation
sooner. Also, it allows the system to remain in closed
loop operation during periods of extended idle.
In Closed Loop operation, the PCM monitors cer-
tain O2 sensor input(s) along with other inputs, and
adjusts the injector pulse width accordingly. During
Open Loop operation, the PCM ignores the O2 sensor
input. The PCM adjusts injector pulse width based
14 - 46 FUEL INJECTION - GASOLINEBR/BE
MANIFOLD ABSOLUTE PRESSURE SENSOR (Continued)