
Also like the cam and crank sensors, a 5 volt ref-
erence is supplied from the PCM and returns a volt-
age 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 of0Ð15psithe
voltage changes 4.0V. The sensor is supplied a regu-
lated 4.8 to 5.1 volts to operate the sensor. Like the
cam and crank sensors ground is provided through
the sensor return circuit.
The MAP sensor input is the number one contrib-
utor to pulse width. The most important function of
the MAP sensor is to determine barometric pressure.
The PCM needs to know if the vehicle is at sea level
or is it in Denver at 5000 feet above sea level,
because the air density changes with altitude. It will
also help to correct for varying weather conditions. If
a hurricane was coming through the pressure would
be very, very low or there could be a real fair
weather, high pressure area. This is important
because as air pressure changes the barometric pres-
sure changes. Barometric pressure and altitude have
a direct inverse correlation, as altitude goes up baro-
metric goes down. The first thing that happens as
the key is rolled on, before reaching the crank posi-
tion, the PCM powers up, comes around and looks at
the MAP voltage, 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 voltage again, continuously every 12 milliseconds,
and compares the current voltage to what it was at
key on. The difference between current 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 known good sensor in
you work area.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, based upon
TPS angle and RPM it will update barometric pres-
sure in the MAP memory cell. With periodic updates,
the PCM can make its calculations more effectively.
The PCM uses the MAP sensor to aid in calculat-
ing the following:
²Barometric pressure
²Engine load
²Manifold pressure
²Injector pulse-width
²Spark-advance programs
²Shift-point strategies (F4AC1 transmissions
only, via the PCI bus)
²Idle speed
²Decel fuel shutoff
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; as pressure
changes, voltage changes proportionately. The range
of voltage output from the sensor is usually between
4.6 volts at sea level to as low as 0.3 volts at 26 in. of
Hg. Barometric pressure is the pressure exerted by
the atmosphere upon an object. At sea level on a
standard day, no storm, barometric pressure is 29.92
in Hg. For every 100 feet of altitude barometric pres-
sure drops .10 in. Hg. If a storm goes through it can
either add, high pressure, or decrease, low pressure,
from what should be present for that altitude. You
should make a habit of knowing what the average
pressure and corresponding barometric pressure is
for your area.
REMOVAL
REMOVAL - 2.4L
(1) Disconnect the negative battery cable.
(2) Disconnect electrical connector and vacuum
hose from MAP sensor (Fig. 20).
(3) Remove two screws holding sensor to the
intake manifold.
REMOVAL - 3.3/3.8L
(1) Disconnect the negative battery cable.
(2) Remove vacuum hose and mounting screws
from manifold absolute pressure (MAP) sensor (Fig.
21).
(3) Disconnect electrical connector from sensor.
Remove sensor.
Fig. 21 MAP SENSOR - 3.3/3.8L
RSFUEL INJECTION14-35
MAP SENSOR (Continued)

(2) Install sensor and tighten to 27 N´m (20 ft.
lbs.) (Fig. 23).
(3) Connect the electrical connector for the O2 sen-
sor and install onto bracket.
(4) Lower vehicle.
(5) Connect the negative battery cable.
INSTALLATION - UPSTREAM 1/1 - 3.3/3.8L
The engines uses two heated oxygen sensors.
(1) After removing the sensor, the exhaust mani-
fold threads must be cleaned with an 18 mm X 1.5 +
6E tap. If reusing the original sensor, coat the sensor
threads with an anti-seize compound such as Loctite
771- 64 or equivalent. New sensors have compound
on the threads and do not require an additional coat-
ing.
(2) Install sensor and tighten to 27 N´m (20 ft.
lbs.).
(3) Connect the electrical connector for the O2 sen-
sor and install onto bracket.
(4) Connect the electrical connector for the speed
control servo.
(5) Install the speed control servo and bracket
refer to the Speed Control Servo for more informa-
tion.
(6) Connect the speed control vacuum harness to
servo.
(7) Install the battery tray, refer to the Battery
section for more information.
(8) Install battery, refer to the Battery section for
more information.
INSTALLATION DOWNSTREAM 2/1 -
2.4/3.3/3.8L
The O2S is located on the side of the catalytic con-
verter.
Threads of new oxygen sensors are factory coated
with anti-seize compound to aid in removal.DO
NOT add any additional anti-seize compound to
the threads of a new oxygen sensor.
(1) Install sensor and tighten to 27 N´m (20 ft.
lbs.).
(2) Connect the electrical connector.
(3) Lower vehicle.
(4) Install the negative battery cable.
THROTTLE BODY
DESCRIPTION
The throttle body is located on the intake manifold
(Fig. 28) or (Fig. 29). Fuel does not enter the intake
manifold through the throttle body. Fuel is sprayed
into the manifold by the fuel injectors.
OPERATION
Filtered air from the air cleaner enters the intake
manifold through the throttle body. The throttle body
contains an air control passage controlled by an Idle
Air Control (IAC) motor. The air control passage is
used to supply air for idle conditions. A throttle valve
(plate) is used to supply air for above idle conditions.
Certain sensors are attached to the throttle body.
The accelerator pedal cable, speed control cable are
connected to the throttle body cam.
Fig. 28 IAC VALVE 2.4L
1 - Idle Air Control Valve
2 - Throttle Position Sensor
Fig. 29 IAC VALVE LOCATION 3.3/3.8L
1 - Idle Air Control Valve
2 - Throttle Position Sensor
RSFUEL INJECTION14-39
O2 SENSOR (Continued)

OPERATION
The signal represents throttle blade position. As
the position of the throttle blade changes, the resis-
tance of the TPS changes.
The PCM supplies approximately 5 volts to the
TPS. The TPS output voltage (input signal to the
powertrain control module) represents throttle blade
position. The TPS output voltage to the PCM varies
from approximately 0.6 volt at minimum throttle
opening (idle) to a maximum of 4.5 volts at wide open
throttle.Along with inputs from other sensors, the PCM
uses the TPS input to determine current engine oper-
ating conditions. The PCM also adjusts fuel injector
pulse width and ignition timing based on these
inputs.
REMOVAL - 3.3/3.8L
(1) Disconnect the negative battery cable.
(2) Remove the electrical connector from the Inlet
Air Temperature sensor.
(3) Remove the air cleaner box lid. Remove hose
from throttle body.
(4) Disconnect the electrical connector at TPS.
(5) Disconnect the electrical connector at IAC.
(6) Remove the throttle and speed control cables
from throttle body.
(7) Remove 3 mounting bolts from throttle body.
(8) Remove throttle body.
(9) Disconnect the purge vacuum line from the
throttle body.
(10) Remove TPS from throttle body.
INSTALLATION - 3.3/3.8L
(1) Install TPS to throttle body.
(2) Disconnect the purge vacuum line from the
throttle body.
(3) Install throttle body.
(4) Install 3 mounting bolts from throttle body.
Tighten bolts.
(5) Install the throttle and speed control cables to
throttle body.
(6) Connect the electrical connector at TPS.
(7) Connect the electrical connector at IAC.
(8) Install the air cleaner box lid. Install hose to
throttle body.
(9) Install the electrical connector to the Inlet Air
Temperature sensor.
(10) Connect the negative battery cable.
Fig. 31 Throttle Position SensorÐ3.3/3.8L Engine
1 - Idle Air Control Valve
2 - Throttle Position Sensor
RSFUEL INJECTION14-41
THROTTLE POSITION SENSOR (Continued)

(6) Start engine and let idle just long enough to
circulate power steering fluid through the analyzer
and hoses. Shut off engine.
(7) Check power steering fluid level and add fluid
as necessary. Start engine again and let idle until the
air is out of the fluid.
(8) Gauge should read below 300 psi (2068 kPa). If
above, inspect the hoses for restrictions and repair as
necessary. The initial pressure should be in the range
of 100-275 psi (689-1896 kPa) depending on fluid
temperature. The flow meter should read above 1.5
GPM.
CAUTION: The following test procedure involves
testing maximum pump pressure output and flow
control valve operation. Do not leave valve closed
for more than four seconds as the pump could be
damaged.
NOTE: Power steering pump maximum pressure for
2.4L engines is 1,200 ± 1,350 psi (8,274 ± 9,308
kPa). Power steering pump maximum pressure for
all other engines is 1,400 ± 1,500 psi (9,653 ± 10,342
kPa).
(9) Close analyzer valve fully three times and
record highest pressure indicated each time. All three
readings must be within specifications. If any of the
three power steering pump pressures are above orbelow specifications, replace pump. (Refer to 19 -
STEERING/PUMP - REMOVAL)
CAUTION: Do not force the steering to operate
against the stops for more than 4 seconds at a time
because pump damage can result.
(10) Once the pump has been verified as working
correctly, completely open the valve on the Power
Steering Analyzer. Turn the steering wheel to the
extreme left until the stop in the steering gear is
met. Hold it there for 2±4 seconds, then release it.
Now turn the steering wheel to the right until the
right stop is met. Hold it there for 2±4 seconds, then
release it. Record the stabilized pressure at each
position. Compare the recorded readings to the spec-
ifications. If the output pressures are not within 100
psi (689 kPa) of one another against either stop or
are below specifications, the steering gear is leaking
internally and must be replaced. (Refer to 19 -
STEERING/GEAR - REMOVAL)
DIAGNOSIS AND TESTING - STEERING
SYSTEM DIAGNOSIS CHARTS
NOTE: There are three diagnosis charts following
that cover POWER STEERING NOISE, STEERING
WHEEL FEEL, and POWER STEERING FLUID.
POWER STEERING NOISE
CONDITION POSSIBLE CAUSES CORRECTION
OBJECTIONABLE HISS
OR WHISTLE*1. Damaged or mispositioned
steering column shaft/coupling dash
panel seal.1. Reposition or replace steering
column shaft/coupling dash panel seal.
2. Mis-routed power steering hose. 2. Check routing of power steering
hoses. Ensure hoses do not come in
unwanted contact with other
components and objects.
3. Noisy valve in power steering
gear.3. Replace power steering gear.
RATTLE OR EXCESSIVE
CLUNK**1. Power steering gear loose on front
suspension crossmember.1. Inspect power steering gear
mounting bolts. Replace as necessary.
Tighten to the specified torque.
2. Front suspension crossmember
mounting fasteners loose at frame.2. Tighten the front suspension
crossmember mounting fasteners to the
specified torque.
3. Loose tie rod (outer or inner). 3. Check tie rod pivot points for wear.
Replace worn/loose parts as required.
RSSTEERING19-3
STEERING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
4. Loose lower control arm mounting
bolts at front suspension
crossmember.4. Tighten control arm mounting bolts to
the specified torques.
5. Lower control arm pivot bushing
worn.5. Replace lower control arm pivot
bushing.
6. Loose strut assembly mounting
fasteners at tower or knuckle.6. Tighten strut assembly fasteners to
the specified torque.
7. Power steering fluid hose touching
the body of the vehicle.7. Adjust hose to proper position by
loosening, repositioning, and tightening
attachments to specified torque. Do not
bend tubing.
8. Damaged front suspension
crossmember.8. Replace front suspension
crossmember.
9. Stabilizer bar link ball joints worn. 9. Replace stabilizer bar link.
10. Lug nuts loose. 10. Tighten lug nuts to specifications.
11. Excessive Wheel bearing
free-play.11. Verify correct halfshaft hub nut
torque. Replace hub and bearing if
torque is okay.
12. Internal power steering gear
noise.12. Replace power steering gear.
POPPING NOISE 1. Worn outer tie rod. 1. Check ball joint for free-play;
Replace outer tie rod.
2. Loose inner tie rod. 2. Replace power steering gear.
CHIRP OR SQUEAL
(POWER STEERING
PUMP)1. Loose power steering pump drive
belt.1. Check and adjust power steering
pump drive belt to specifications or
replace automatic tensioner where
applicable. Replace belt if worn or
glazed.
2. Malfuctioning belt auto-tensioner 2. Replace belt auto-tensioner.
WHINE, GROWL, MOAN
OR GROAN (POWER
STEERING PUMP)***1. Low fluid level. 1. Fill power steering fluid reservoir to
proper level and check for leaks (make
sure all air is bled from the system
fluid).
2. Power steering hose touching
vehicle body or frame.2. Adjust hose to proper position by
loosening, repositioning, and tightening
fitting to specified torque. Do not bend
tubing. Replace hose if damaged.
3. Extremely low ambient
temperature.3. Some noise can be expected, but will
go away as vehicle warms. Replace
pump if noise is excessive.
4. Extreme wear of power steering
pump internal components.4. Replace power steering pump and
flush system as necessary.
19 - 4 STEERINGRS
STEERING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
SUCKING AIR SOUND 1. Loose clamp on power steering
fluid return hose.1. Tighten or replace hose clamp.
2. Missing O-Ring on power steering
hose connection.2. Inspect connection and replace
O-Ring as required.
3. Low power steering fluid level. 3. Fill power steering fluid reservoir to
proper level and check for leaks.
4. Loose clamp on fluid supply hose. 4. Tighten or replace hose clamp.
SQUEAK OR RUBBING
SOUND1. Steering column shroud rubbing. 1. Realign shrouds as necessary.
2. Steering column shaft rubbing. 2. Move or realign item rubbing shaft.
3. Clockspring noisy. 3. Remove clockspring. Reinstall wheel.
If noise is gone, replace clockspring.
4. Seal lubrication inadequate. 4. Lube seal (if external).
5. Steering gear internally noisy. 5. Replace steering gear (if no other
cause can be found).
SCRUBBING OR
KNOCKING NOISE.1. Incorrect tire or wheel size. 1. Replace incorrect size tire or wheel
with size used as original equipment.
2. Interference between steering
gear and other vehicle components.2. Check for bent or misaligned
components and correct as necessary.
3. Steering gear internal stops worn
excessively allowing tires to be
steered excessively far.3. Replace steering gear.
* NOTE: There is some noise in all power steering
systems. One of the most common is a hissing
sound evident when turning the steering wheel
when at a standstill or when parking and the steer-
ing wheel is at the end of its travel. Hiss is a very
high frequency noise similar to that experienced
while slowly closing a water tap. The noise is
present in every valve and results when high veloc-
ity fluid passes valve orifice edges. There is no
relationship between this noise and the perfor-
mance of the steering system.** NOTE: A light clunk may be felt or heard during
steering wheel reversal while vehicle is stationary.
This results from internal steering gear rack move-
ment at the bushings and in no way affects the per-
formance of the steering system. This movement
may be felt in the steering components during
steering wheel reversal.
*** NOTE: Power steering pump growl/moan/groan
results from the development of high pressure fluid
flow. Normally this noise level should not be high
enough to be objectionable.
RSSTEERING19-5
STEERING (Continued)

STEERING WHEEL FEEL
CONDITION POSSIBLE CAUSES CORRECTION
STEERING WHEEL/
COLUMN CLICKING,
CLUNKING OR RATTLING.1. Loose steering coupling pinch
bolt.1. Replace pinch bolt and torque to
specifications.
2. Steering column bearings. 2. Replace steering column.
3. Excessive intermediate shaft
coupling free-play.3. Replace intermediate shaft.
STEERING WHEEL HAS
FORE AND AFT
LOOSENESS.1. Steering wheel retaining nut not
properly tightened and torqued.1. Tighten the steering wheel retaining nut
to its specified torque.
2. Steering column lower bearing
spring retainer slipped on steering
column shaft.2. Replace steering column.
3. Loose steering column to
instrument panel fasteners.3. Tighten fasteners to specified torque.
STEERING WHEEL, DASH
OR VEHICLE VIBRATES
DURING LOW SPEED OR
STANDSTILL STEERING
MANEUVERS.1. Air in the fluid of the power
steering system.1. Bleed air from system following the
power steering pump initial operation
service procedure.*
2. Tires not properly inflated. 2. Inflate tires to the specified pressure.
3. Excessive engine vibration. 3. Ensure that the engine is tuned properly.
4. Loose tie rod end jam nut. 4. Tighten the inner to outer tie rod jam nut
to the specified torque.
5.Overcharged air conditioning
system.5.Check air conditioning pump head
pressure and correct as necessary.
6. Grounded engine mount. 6. Repair as necessary.
7. Loose outer tie rod. 7. Replace outer tie rod.
STEERING CATCHES,
SURGES OR STICKS IN
CERTAIN POSITIONS OR
IS DIFFICULT TO TURN. ***1. Low power steering fluid level. 1. Fill power steering fluid reservoir to
specified level and check for leaks.
2. Tires not inflated to specified
pressure.2. Inflate tires to the specified pressure.
3. Lack of lubrication in front lower
control arm ball joints.3. Lubricate ball joints if ball joints are not a
lubricated-for-life type ball joint. If ball joint
is a lubricated-for-life ball joint, replace ball
joint.
4. Worn or binding lower control arm
ball joint.4. Replace lower control arm ball joint.
5. Lack of lubrication in steering gear
outer tie rod ends.5. Lubricate tie rod ends if they are not a
lubricated-for-life type. If tie rod end is a
lubricated-for-life type, replace tie rod end.
19 - 6 STEERINGRS
STEERING (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
EXCESSIVE STEERING
WHEEL KICKBACK OR
TOO MUCH STEERING
WHEEL FREE PLAY.1. Air in the fluid of the power
steering system.1. Bleed air from system following the the
power steering pump initial operation
service procedure.*
2. Power steering gear loose on
cradle/crossmember.2. Inspect power steering gear mounting
bolts. Replace as necessary. Tighten to the
specified torque.
3. Steering column coupling or
intermediate shaft worn, broken or
loose.3. Replace steering column coupling or
intermediate shaft.
4. Free play in steering column. 4. Check all components of the steering
column and repair or replace as required.
5. Worn lower control arm ball joints. 5. Replace lower control arm ball joints as
required.
6. Loose steering knuckle-to-ball joint
stud pinch bolt.6. Inspect pinch bolt, replace as necessary,
and tighten to specified torque.
7. Front wheel bearing loose or
worn.7. Replace hub and bearing as necessary.
8. Loose outer tie rod end. 8. Replace outer tie rod end that has
excessive free play.
9. Loose inner tie rod. 9. Replace power steering gear.
10. Defective steering gear rotary
valve.10. Replace power steering gear.
* NOTE: Steering shudder can be expected in new
vehicles and vehicles with recent steering system
repairs. Shudder should dissipate after the vehicle
has been driven several weeks.
** NOTE: To evaluate this condition, it may be nec-
essary to disconnect the coupling at the base of the
steering column. Turn the steering wheel and feel or
listen for internal rubbing in steering column. To
avoid damaging the column clockspring, note the
following. Before disconnecting coupling, place
tires in the straight-ahead position and center steer-
ing wheel. Once disconnected, DO NOT rotatesteering wheel more than one revolution in either
direction and place steering wheel in original loca-
tion before reconnecting coupling. If this position is
lost, the steering column clockspring must be
recentered following the procedure found within the
procedure for steering column installation in the
steering column section.
*** NOTE: Increased low speed or stationary steer-
ing effort can be expected if the steering fluid is at
a high temperature. High fluid temperature usually
results from high engine rpm due to trailer towing,
ascending grades, or racing the engine for pro-
longed periods of time.
POWER STEERING FLUID
CONDITION POSSIBLE CAUSES CORRECTION
LOW FLUID LEVEL WITH
VISIBLE LEAK.1. Loose power steering hose
fittings.1. Tighten the fitting to its specified torque.
2. Damaged or missing fitting seal,
gasket, or O-ring.2. Replace as necessary.
3. Power steering component
leaking.3. Repair or replace the leaking component
as required.
19 - 8 STEERINGRS
STEERING (Continued)