Chrysler Stratus Convertible. Manual — part 28

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 (Table 1). Barometric pressure is the pressure
exerted by the atmosphere upon an object. At sea
level on a standard day, no storm, barometric pres-
sure is 29.92 in Hg. For every 100 feet of altitude
barometric pressure 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. Always use the Diagnostic
Test Procedures Manual for MAP sensor testing.

POWER STEERING PRESSURE SWITCH—PCM
INPUT

DESCRIPTION

A pressure sensing switch is located on the power

steering gear.

OPERATION

The switch (Fig. 5) provides an input to the PCM

during periods of high pump load and low engine
RPM; such as during parking maneuvers.

When power steering pump pressure exceeds 4137

kPa (600 psi), the switch is open. The PCM increases
idle air flow through the IAC motor to prevent
engine stalling. When pump pressure is low, the
switch is closed.

SENSOR RETURN—PCM INPUT

OPERATION

The sensor return circuit provides a low electrical

noise ground reference for all of the systems sensors.
The sensor return circuit connects to internal ground

circuits

within

the

Powertrain

Control

Module

(PCM).

SCI RECEIVE—PCM INPUT

OPERATION

SCI Receive is the serial data communication

receive circuit for the DRB scan tool. The Powertrain
Control Module (PCM) receives data from the DRB
through the SCI Receive circuit.

THROTTLE POSITION SENSOR—PCM INPUT

DESCRIPTION

The throttle position sensor mounts to the side of

the throttle body (Fig. 6).

OPERATION

The Throttle Position Sensor (TPS) connects to the

throttle blade shaft. The TPS is a variable resistor
that provides the PCM with an input signal (voltage).
The signal represents throttle blade position. As the
position of the throttle blade changes, the resistance
of the TPS changes.

The PCM supplies approximately 5 volts DC to the

TPS. The TPS output voltage (input signal to the
PCM) represents throttle blade position. The TPS
output voltage to the PCM varies from approximately
0.5 volt at minimum throttle opening (idle) to a max-
imum of 3.7 volts at wide open throttle.

Along with inputs from other sensors, the PCM

uses TPS input to determine current engine operat-
ing conditions. The PCM also adjusts fuel injector

Fig. 5 Power Steering Pressure Switch

1 – POWER STEERING PRESSURE SWITCH

Fig. 6 Throttle Position Sensor—2.0L Engines

1 – TPS
2 – IAC
3 – THROTTLE CONTROL SHIELD

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FUEL SYSTEM

14 - 29

DESCRIPTION AND OPERATION (Continued)

pulse width and ignition timing based on these
inputs.

VEHICLE SPEED SIGNAL—PCM INPUT

DESCRIPTION

The vehicle speed sensor is located in the transmis-

sion extension housing (Fig. 7).

OPERATION

AUTOMATIC

The transaxle control module (TCM) supplies the

vehicle speed signal to the PCM based on the output
shaft speed. The PCM sends a 5 volt signal to the
TCM. The TCM switches this signal to a ground, and
then opens the circuit at a rate of 8000 pulses per
mile. When the PCM counts 8000 pulses, the PCM
assumes the vehicle has traveled one mile. The out-
put speed sensor is located on the side of the tran-
saxle (Fig. 8).

The speed and distance signals, along with a closed

throttle signal from the TPS, determine if a closed
throttle deceleration or normal idle condition (vehicle
stopped) exists. Under deceleration conditions, the
PCM adjusts the idle air control motor to maintain a
desired MAP value. Under idle conditions, the PCM
adjusts the idle air control motor to maintain a
desired engine speed.

MANUAL

The sensor input is used by the PCM to determine

vehicle speed and distance traveled.

The vehicle speed sensor generates 8 pulses per

sensor revolution. These signals, in conjunction with
a closed throttle signal from the throttle position sen-

sor, indicate a closed throttle deceleration to the
PCM.

Under

deceleration

conditions,

the

PCM

adjusts the Idle Air Control (IAC) motor to maintain
a desired MAP value.

When the vehicle is stopped at idle, a closed throt-

tle signal is received by the PCM (but a speed sensor
signal is not received). Under idle conditions, the
PCM adjusts the IAC motor to maintain a desired
engine speed.

The vehicle speed sensor signal is also used to

operate the following functions or systems:

• Speedometer

• Speed control

• Daytime Running Lights (Canadian Vehicles

only).

AUTOMATIC SHUTDOWN RELAY—PCM
OUTPUT

DESCRIPTION

The ASD relay and fuel pump relay are located in

the Power Distribution Center (PDC) near the Air
Cleaner (Fig. 9). The inside top of the PDC cover has
a label showing relay and fuse location. They are ISO
relays.

OPERATION

The PCM operates the Automatic Shut Down

(ASD) relay and fuel pump relay through one ground
path. The PCM operates them by switching the
ground path for the relays on and off.

The ASD relay connects battery voltage to the fuel

injectors and ignition coil. The fuel pump relay con-
nects battery voltage to the fuel pump.

Fig. 7 Vehicle Speed Sensor—Manual Transmission

1 – TRANSAXLE
2 – SPEED SENSOR
3 – SPEED SENSOR RETAINING BOLT

Fig. 8 Output Speed Sensor—Automatic Transaxle

1 – OUTPUT SPEED SENSOR
2 – PARK/NEUTRAL SWITCH (BLACK)
3 – TRANSMISSION RANGE SWITCH

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FUEL SYSTEM

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DESCRIPTION AND OPERATION (Continued)

The PCM turns the ground path off when the igni-

tion switch is in the Off position. Both relays are off.
When the ignition switch is in the On or Crank posi-
tion, the PCM monitors the crankshaft position sen-
sor

and

camshaft

position

sensor

signals

to

determine engine speed. If the PCM does not receive
a crankshaft position sensor signal and camshaft
position sensor signal when the ignition switch is in
the Run position, it de-energizes both relays. When
the relays are de-energized, battery voltage is not
supplied to the fuel injectors, ignition coil and fuel
pump.

PROPORTIONAL PURGE SOLENOID—PCM
OUTPUT

DESCRIPTION

The solenoid attaches to a bracket near the front

engine mount (Fig. 10). To operate correctly, the sole-
noid must be installed with the electrical connector
on top.

OPERATION

The purge solenoid regulates the rate of vapor flow

from the EVAP canister to the throttle body. The
PCM operates the solenoid.

During the cold start warm-up period and the hot

start time delay, the PCM does not energize the sole-
noid. When de-energized, no vapors are purged.

The proportional purge solenoid operates at a fre-

quency of 200 hz and is controlled by an engine con-
troller circuit that senses the current being applied
to the proportional purge solenoid and then adjusts
that current to achieve the desired purge flow. The
proportional purge solenoid controls the purge rate of
fuel vapors from the vapor canister and fuel tank to
the engine intake manifold.

IDLE AIR CONTROL MOTOR—PCM OUTPUT

DESCRIPTION

The Idle Air Control (IAC) motor is mounted on the

throttle body. The PCM operates the idle air control
motor (Fig. 11).

OPERATION

The PCM adjusts engine idle speed through the

idle air control motor to compensate for engine load,
coolant temperature or barometric pressure changes.

The throttle body has an air bypass passage that

provides air for the engine during closed throttle idle.
The idle air control motor pintle protrudes into the
air bypass passage and regulates air flow through it.

The PCM adjusts engine idle speed by moving the

IAC motor pintle in and out of the bypass passage.
The adjustments are based on inputs the PCM
receives. The inputs are from the throttle position
sensor, crankshaft position sensor, coolant tempera-
ture sensor, MAP sensor, vehicle speed sensor and

Fig. 9 Power Distribution Center (PDC)

1 – BATTERY POSITIVE
2 – BATTERY GROUND
3 – AIR CLEANER
4 – PCM
5 – PDC
6 – TCM

Fig. 10 Proportional Purge Solenoid

1 – TEST PORT
2 – PROPORTIONAL PURGE SOLENOID

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FUEL SYSTEM

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DESCRIPTION AND OPERATION (Continued)

various switch operations (brake, park/neutral, air
conditioning).

When engine rpm is above idle speed, the IAC is

used for the following functions:

• Off-idle dashpot

• Deceleration air flow control

• A/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)

Target Idle

Target idle is determined by the following inputs:
• Gear position

• ECT Sensor

• Battery voltage

• Ambient/Battery Temperature Sensor

• VSS

• TPS

• MAP Sensor

DATA LINK CONNECTOR

DESCRIPTION

The data link connector is located inside the vehi-

cle, under the instrument panel, at the driver’s kick
panel (Fig. 12).

OPERATION

The data link connector (diagnostic connector)

links the DRB scan tool with the Powertrain Control
Module (PCM). Refer to On-Board Diagnostics in the
Emission Control section.

MALFUNCTION INDICATOR (CHECK ENGINE)
LAMP—PCM OUTPUT

DESCRIPTION

Refer to the Instrument Panel Systems for more

information.

OPERATION

The PCM supplies the malfunction indicator (check

engine) lamp on/off signal to the instrument panel
through the CCD Bus. The CCD Bus is a communi-
cations port. Various modules use the CCD Bus to
exchange information.

The Check Engine lamp comes on each time the

ignition key is turned ON and stays on for 3 seconds
as a bulb test.

The Malfunction Indicator Lamp (MIL) stays on

continuously, when the PCM has entered a Limp-In
mode or identified a failed emission component. Dur-
ing Limp-in Mode, the PCM attempts to keep the
system operational. The MIL signals the need for
immediate service. In limp-in mode, the PCM com-
pensates for the failure of certain components that
send incorrect signals. The PCM substitutes for the
incorrect signals with inputs from other sensors.

If the PCM detects active engine misfire severe

enough to cause catalyst damage, it flashes the MIL.
At the same time the PCM also sets a Diagnostic
Trouble Code (DTC).

For signals that can trigger the MIL (Check

Engine Lamp) refer to the On-Board Diagnos-
tics Chart.

Fig. 11 Idle Air Control Motor Air Bypass Passage—

2.0L

1 – IDLE AIR CONTROL MOTOR
2 – FRESH AIR OPENING

Fig. 12 Data Link (Diagnostic) Connector

1 – HOOD RELEASE
2 – DIAGNOSTIC CONNECTOR
3 – DRIVER’S SIDE KICK PANEL

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FUEL SYSTEM

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DESCRIPTION AND OPERATION (Continued)