Chrysler Cirrus, Dodge Stratus, Plymouth Breeze Haynes. Manual - part 22

6-6

Chapter 6 Emissions and engine control systems

Trouble codes - using scan tool (continued)

Note: These are "generic" trouble codes and pertain to all models covered by this manual.

Code

Probable cause

P0356..........................Ignition coil no. 6 primary circuit fault
P0400..........................EGR flow fault
P0401.......................... EGR insufficient flow detected
P0402..........................EGR excessive flow detected
P0403..........................EGR transducer circuit open or shorted
P0420..........................Catalyst system efficiency below threshold (Bank 1)
P0421.......................... Catalyst system efficiency below threshold (Bank 1)
P0430..........................Catalyst system efficiency below threshold (Bank 2)
P0431.......................... Catalyst system efficiency below threshold (Bank 2)
P0442..........................EVAP small leak detected
P0443..........................EVAP VMV circuit fault
P0452..........................EVAP fuel tank pressure sensor low input
P0453..........................EVAP fuel tank pressure sensor high input
P0455..........................Leak in EVAP system detected
P0462..........................Fuel level sending unit - low voltage indicated
P0463..........................Fuel level sending unit - high voltage indicated
P0460..........................Fuel level sending unit - no movement detected
P0500......................... VSS fault
P0505..........................IAC valve system fault
P0600..........................PCM internal fault
P0601 .......................... PCM internal fault
P0603..........................PCM Keep Alive Memory test error
P0605..........................PCM Read Only Memory test error
P0622......................... Alternator field circuit open or shorted
P0645......................... A/C clutch relay circuit open or shorted
P0700......................... Automatic transmission fault detected
P0703..........................Brake switch stuck open or closed

Information sensors and output

actuators - description, check
and replacement

Note 1: All models covered by this manual
are equipped with the OBD-ll system. The
engine codes on 1997 and earlier models can
be accessed using the ignition key, but it is
necessary to use a special factory SCAN tool
(DRB-1l) to read and interpret all the various
levels of diagnostic information (or any trou-
ble codes on 1998 and later models). Have
the vehicle diagnosed by a dealer service
department or other qualified repair shop if
the following component checking proce-
dures fail to identify and correct a problem.
Note 2: After performing checking proce-
dures on any of the OBD-ll components, be
sure to clear the PCM of all trouble codes by
disconnecting the negative cable from the
remote battery terminal for at least ten sec-
onds.

Air

conditioning clutch relay

General description

If the vehicle is equipped with air condi-

tioning, the PCM controls the application of
the air conditioning compressor clutch. The
PCM uses the air conditioning clutch relay to

delay clutch engagement when the air condi-
tioning is turned ON to allow the IAC motor to
adjust the engine idle speed to compensate
for the additional load. The PCM will also dis-
engage the A/C compressor clutch if the

refrigerant pressure is too high or too low, the

engine coolant temperature is too hot, when
the throttle is placed in the wide-open posi-
tion or the PCM senses a part-throttle launch
condition.

Check and replacement

Refer to illustration 3.3
2

First check for battery voltage to the air

conditioning clutch with the engine running
and the air conditioning turned ON. Detach
the electrical connector from the air condi-
tioning compressor and using a test light or a
voltmeter check for battery voltage at the
connector dark blue/black wire.
3

If voltage is not present at the connec-

tor, check for voltage to the air conditioning
compressor clutch relay, which is located
under the rectangular cover of the Power Dis-
tribution Center (PDC). Remove the relay
from the PDC. With the engine running and
the air conditioning ON, check for battery
voltage to terminals 39 and 19 (see illustra-
tion). If voltage is present, replace the relay. If
voltage is not present at the connector, refer
to Chapter 3 for more information on trou -

3.3 Terminal guide for the air conditioning

compressor clutch relay socket

bleshooting the air conditioning system. In
most cases, if the air conditioning system
does not operate, a problem exists with the
air conditioning pressure switches or controls
and not the PCM.
4

To replace the air conditioning clutch

relay, remove the cover from the PDC and
pull the relay out of its socket. Installation is

the reverse of removal.

Brake switch

General description

When the brakes are applied, the brake

switch sends a signal to the PCM. After

receiving this input, the PCM maintains idle

speed to a scheduled rpm via the IAC motor.

Chapter 6 Emissions and engine control systems

6-7

Check and replacement

Refer to Chapter 9 for service proce-

dures.

Camshaft position sensor

General description

Refer to illustrations 3.7a and 3.7b
7

On four-cylinder engines, the camshaft

position sensor, located at the rear of the
cylinder head (see illustrations), provides
cylinder identification to the PCM to synchro-
nize the fuel system with the ignition system.
The synchronizing signal is generated from a
rotating target magnet attached to the rear of
the camshaft. The target magnet has four dif-
ferent poles arranged in a symmetrical pat-
tern. As the target magnet rotates, the sensor
senses the changes in polarity and generates
pulses from high (5 volts) to low (0.30 volts).
These voltage pulses combined with the data
from the crankshaft sensor are processed by
the PCM which then determines fuel injection
synchronization. On 2.0L DOHC and 2.4L
four-cylinder engines, the sensor also acts as
a thrust plate to control camshaft endplay.
8

On V6 engines the camshaft position

sensor is located inside the distributor which
is located on the right side (rear) cylinder
head and driven by the camshaft. The
camshaft position sensor is a Hall Effect
device which detects a rotating ring (shutter)
mounted to the distributor shaft. When the
leading edge of the shutter enters the Hall
Effect device, the interruption of the magnetic
field causes a signal of approximately 5 volts
to be sent to the PCM. As the trailing edge of
the shutter leaves the device, the voltage sig-
nal is turned off. These voltage pulses com-
bined with the data from the crankshaft sen-
sor are processed by the PCM which then
determines fuel injection synchronization.

Check

Refer to illustration 3.9

Note: To backprobe an electrical connector,

use pins or paper clips inserted into the rear
of the connector (or wire) to facilitate meter
attachment. Be careful not to short the

probes during this process.

3.7b Camshaft position sensor - 2.0L

DOHC and 2.4L engines

With the ignition key in the ON position

(engine OFF), check for supply voltage at the
ORANGE/WHITE wire (1995 to 1997 vehicles)
or the ORANGE wire (1998 and later vehicles)
at the camshaft position sensor connector
(four-cylinder engines) and the distributor
connector (V6 engines) (see illustration). The
supply voltage should be approximately 8
volts. If no voltage is present, check the circuit
for a broken wire or short (see Chapter 12). If
the circuit checks out OK, have the PCM
checked out by your local dealer service
department or other qualified repair shop.
10

Next, disconnect the spark plug wires

from the ignition coil (four-cylinder engines)
or the distributor cap (V6 engine) (see Chap-
ter 1 if necessary). With the connector
attached to the sensor, use a voltmeter to
backprobe the tan/yellow signal wire (posi-
tive) and the black/light blue ground wire and
crank the engine. The voltmeter should fluc-
tuate from approximately 0.3 to 5 volts for
four-cylinder engines and 0 to 5 volts for V6
engines. If supply voltage is detected but
there is no signal voltage, replace the
camshaft sensor. After testing, replace the
spark plug wires in their proper positions.

Replacement

Four-cylinder engines

Disconnect the negative battery cable

from the ground stud on the left shock tower
(see Chapter 5, Section 1).
12

Remove the air cleaner assembly (see

Chapter 4).
13

On 2.0L SOHC engines, disconnect the

electrical connectors from the engine coolant
sensor and camshaft position sensor.
Remove the brake booster hose and electri-
cal connectors from the holders on the end of
the valve cover.
14

Remove the bolts from the camshaft

sensor and withdraw the sensor from the rear
of the cylinder head.
15 If necessary, remove the target magnet
mounting screw and remove the magnet.
16 Installation is the reverse of removal. If
removed, align the locating pins on the back-
side of the target magnet with the locating

3.9 On V6 engines, the camshaft position

sensor is located inside the distributor.

The 6-pin electrical connector (arrow)

contains the sensor wires - the 2-pin

electrical connector is for the ignition

coil circuit

holes in the rear of the camshaft. Tighten the
fasteners to the torques listed in this Chap-
ter's Specifications.

V6 engines

17 If the camshaft position sensor is deter-

mined to be defective, replace the distributor
assembly (see Chapter 5).

Crankshaft position sensor

General description

Refer to illustrations 3.18a and 3.18b

The PCM uses the crankshaft position

sensor to determine fuel injector sequence,
ignition

ti ming and engine rpm. The

crankshaft position sensor is a Hall-Effect
device which uses cut-outs in the crankshaft
(four-cylinder engines) or slots is the drive-

plate (V6 engine) to send voltage pulses to

the PCM. The fuel injection and ignition sys-
tems will not operate if the PCM does not
receive a signal from the crankshaft position
sensor.

On four-cylinder engines, the

crankshaft position sensor is located on the
side of the engine block between the main

bearing cap/bedplate and engine block near

the oil filter (see illustration). On V6 engines,

3.18a Crankshaft position sensor - four-

cylinder engines

6-8

Chapter 6 Emissions and engine control systems

3.18b Crankshaft position sensor - V6 engine

3.33a On 2.0L four-cylinder engines, the Engine Coolant

Temperature (ECT) sensor (arrow) is located at the rear of the

cylinder head

CRANKSHAFT

POSITION SENSOR

ENGINE COOLANT

TEMPERATURE

SENDING UNIT

3.3313 On 2.4L four-cylinder engines, the

Engine Coolant Temperature (ECT) sensor

is located at the front of the cylinder head

3.33c On V6 engines, the Engine Coolant

Temperature (ECT) sensor (arrow) is

located at the rear of the cylinder head

near the engine coolant filler neck

the crankshaft position sensor is located on
the transaxle bellhousing and below the dis-
tributor (see illustration).

Check

Note 1: To perform this check on four-cylin-
der engines, it is necessary to raise the front
of the vehicle and place it securely on jack-

stands. On V6 engines, it will be necessary to

detach the speed control servo from the left

shock tower, if equipped.

Note 2: To backprobe an electrical connec-
tor, use pins or paper clips inserted into the

rear of the connector (or wire) to facilitate
meter attachment. Be careful not to short the
probes during this process.

Check the supply voltage to the

crankshaft sensor from the PCM. Locate the
crankshaft sensor electrical connector. With

the ignition key ON (engine OFF) backprobe
the orange/white wire (positive) using a volt-

meter. There should be approximately 8.0

volts present. If no voltage is present, check
the circuit for a broken wire or short (see
Chapter 12). If the circuit checks out OK,

have the PCM checked out by your local

dealer service department or other qualified

repair shop.

Next, disconnect the spark plug wires

from the ignition coil (four-cylinder engines)
or the distributor cap (V6 engine) (see Chap-
ter 1 if necessary). With the connector
attached to the sensor, use a voltmeter to
backprobe the gray/black signal wire (posi-
tive) and the black/light blue ground wire and
crank the engine. The voltmeter should fluc-
tuate from approximately 0.3 to 5 volts. If
supply voltage is detected but there is no sig-
nal voltage, replace the crankshaft sensor.
After testing, replace the spark plug wires in
their proper positions.

Replacement

Four-cylinder engines
21

Raise the front of the vehicle and sup-

port it securely on jackstands.
22

Disconnect the crankshaft sensor wiring

harness connector.
23

Remove the mounting bolt and with-

draw the crankshaft sensor from the engine
block.

24 Installation is the reverse of removal.

Tighten the bolt to the torque listed in this

Chapter's Specifications and lower the vehi-
cle.

V6 engine

25 If equipped, detach the speed control
servo from the left shock tower and position
it out of the way.

Detach the crankshaft sensor wiring

harness connector from the heater tube
bracket and disconnect the electrical con-
nector.

Remove the mounting bolt and with-

draw the crankshaft sensor from the
transaxle bellhousing.
28 If the old sensor is to be re-installed,

remove the paper spacer from the sensor

face and install a new spacer. If installing a

new sensor, verify the paper spacer is
installed on the face.

Place the sensor in the bellhousing and

install the mounting bolt loosely.
30 If the crankshaft sensor mounting hole is
elongated, push the sensor down into the
bellhousing until contact is made with the
driveplate. Tighten the mounting bolt to the
torque listed in this Chapter's Specifications
(the paper spacer locates the sensor in the

proper position and will rub off during opera-
tion).
31

If the sensor does not have an elon-

gated hole, simply install the sensor and
tighten the mounting bolt to the torque listed
in this Chapter's Specifications.
32

The remaining installation steps are the

reverse of removal.

Engine Coolant Temperature

(ECT) sensor

General description

Refer to illustrations 3.33a, 3.33b and 3.33c

The ECT sensor is a thermistor (a resis-

tor which varies the value of its resistance in

accordance with temperature changes) (see
illustrations). The change in the resistance

values will directly affect the voltage signal
from the coolant thermosensor. As the sen-
sor temperature DECREASES, the resistance
values will INCREASE. As the sensor temper-
ature INCREASES, the resistance values will

DECREASE.

Check

Note: On V6 engines it will be necessary to

remove the air cleaner assembly (see Chap-
ter 4) before performing this test.

Chapter 6 Emissions and engine control systems

6-9

3.37 If you're re-installing the old ECT

sensor, wrap the threads with Teflon tape

to prevent leakage

To check the ECT sensor, release the

locking tab and disconnect the electrical con-
nector. Using an ohmmeter across the sensor

terminals, measure the resistance of the ECT
sensor with the engine cold (approximately

70-degrees F). The ECT resistance value

should be between 7,000 and 13,000 ohms.

Next, start the engine and allow it to reach
operating temperature (approximately 200-
degrees F), then turn off the engine. Measure

the ECT resistance again, the resistance

should be between 700 and 1,000 ohms.
Note: Since the coolant sensor is difficult to

access on some vehicles, it may be easier to

remove the sensor and perform the tests in a
pan of heated water where the water temper-
ature can be controlled.

Replacement

Refer to illustration 3.37
Warning: Wait until the engine is completely
cool before beginning this procedure.
35

Drain the cooling system until the

coolant level is below the sensor (see Chap-
ter 1).
36

Release the locking tab and disconnect

the electrical connector, then carefully

unscrew the sensor. Caution: Handle the

coolant sensor with care. Damage to this sen-
sor will affect the operation of the entire fuel
injection system.
37 If you are re-installing the old sensor,
clean the threads and then wrap them with
Teflon tape to prevent leakage and thread
corrosion (see illustration). Note: New ECT
sensors have sealant already applied to the
threads.
38 Installation is the reverse of removal.
Tighten the ECT sensor to the torque listed in
this Chapter's Specifications. Refill the cool-

ing system after installation (see Chapter 1).

Idle Air Control (IAC) motor

This output actuator controls the engine

idle speed. For service procedures on the
IAC motor, refer to Chapter 4. A failure in the
IAC motor circuit will set a code 25 in the
PCM memory.

Intake Air Temperature (IAT)
sensor

Note: 1995 models with 2.0L SOHC engines

came equipped with an IAT sensor and a
MAP sensor. On 1996 and later models, the
IAT sensor is combined with the MAP sensor
into a single unit.

General information

Refer to illustrations 3.40a, 3.40b and 3.40c
40

The Intake Air Temperature sensor is

located in the intake manifold (see illustra-

tions). This sensor operates as a negative
temperature coefficient (NTC) device. As the
sensor temperature DECREASES, the resis-
tance values will INCREASE. As the sensor
temperature INCREASES, the resistance val-

ues will DECREASE. Most cases, the appro-
priate solution to the problem will be either
repair of a wire or replacement of the sensor.

Check

Refer to illustration 3.41

Note: On 2.4L four-cylinder engines, the air

cleaner assembly must be removed (see
Chapter 4) before this check can be per-
formed. Since the IAT sensor is difficult to
access on 2.4L models, it may be easier to
remove the sensor and perform the check on
a workbench and heat the sensor using a heat
gun or hair dryer.
41

To check the sensor, release the locking

tab and disconnect the electrical connector

3.40a On 1996

and later 2.0L

SOHC engines,

the IAT and MAP

sensors are

combined into

one unit

3.40b On 2.4L and 2.0L DOHC engines, the IAT sensor is

located on the intake manifold on the cylinder head side

3.40c On V6 engines, the MAP (A) and IAT (B) sensors are located

on the right (passenger) side of the upper intake manifold -

manifold removed for clarity

3.41 Disconnecting the electrical connector from the IAT sensor -

V6 engine shown

6-10

Chapter 6

Emissions and

engine

control

systems

3.47 Knock sensor (four-cylinder engines)

as viewed from under the vehicle

(see illustration). Using an ohmmeter across

the sensor terminals, measure the resistance

of the sensor at ambient temperature
(approximately 70-degrees F). The resistance
should be between 7,000 and 13,000 ohms.
Next, start the engine and allow it to reach
operating temperature (approximately 200-
degrees F). Measure the resistance again - it

should be between 700 and 1,000 ohms.

Replacement

On 1996 and later models with 2.0L

four-cylinder engines, refer to the MAP sen-
sor removal procedure in this Section.
43

On 2.4L four-cylinder engines, remove

the air cleaner assembly (see Chapter 4). To
gain access to the IAT sensor, reach between
the intake manifold and the cylinder head

inserting your hand at the throttle body end.
Perform this operation when the engine tem-
perature is cold to avoid burning yourself.

Release the locking tab and disconnect

the electrical connector from the sensor.
45

Unscrew and remove the sensor from

the intake manifold.
46 Installation is the reverse of removal.
Tighten the IAT sensor to the torque given in
this Chapter's Specifications.

Knock sensor -

our-cylinder

engines

General information

Refer to illustration 3.47
47

Four-cylinder engines are equipped with

a knock sensor mounted on the side of the
engine block near the starter motor (see
illustration). The knock sensor is a piezo-
electric crystal that oscillates with engine
vibration. When knock is detected, the PCM

retards the ignition timing until the knocking

stops.

Check

Note 1: 1995 to 1997 models operate on
direct current (dc), 1998 and later models use
alternating current (ac).
Note 2: To backprobe an electrical connec-
tor, use pins or paper clips inserted into the

3.57 Typical MAP sensor electrical

connector - inset shows 1996 and later

2.0L engine MAP/IAT sensor connector

rear of the connector (or wire) to facilitate
meter attachment. Be careful not to short the
probes during this process.
48

Raise the front of the vehicle and sup-

port it securely on jackstands.

Disconnect the sensor electrical con-

nector.

Using a voltmeter (switched to the

proper setting - see Note above), connect the
negative probe to ground, and the positive
probe to the knock sensor electrical connec-

tor black/light green wire. Turn the ignition
switch ON (engine off). The voltmeter should

indicate approximately 4 volts (dc) for 1995 to
1997 models and 600 mV (ac) for 1998 mod-

els. Turn OFF the ignition. If no voltage is

indicated, check for a blown fuse and exam-
ine the wires for obvious damage. If the cir-

cuit looks OK, have the PCM checked out at
your local dealer service department or other
qualified repair shop.
51

Install the sensor electrical connector

onto the sensor. Using a voltmeter, back-

probe the knock sensor electrical terminals

(positive probe to black/light green wire).
Turn the ignition key ON (engine off).
52

While watching the voltmeter, lightly tap

the metal part of the sensor body with a
wrench. The voltmeter should start to jump
as the sensor is triggered. Turn OFF the igni-
tion. If the voltage doesn't fluctuate, replace
the sensor.

Replacement

Raise the front of the vehicle and sup-

port it securely on jackstands.
54

Disconnect the electrical connector and

unscrew the knock sensor from the engine
block.
55 Installation is the reverse of removal.
Tighten the knock sensor to the torque listed
in this Chapter's Specifications.

Manifold Absolute Pressure
(MAP) sensor

Note: 1995 models with 2.0L SOHC engines
came equipped with an /AT sensor and a
MAP sensor. On 1996 and later models, the

3.62a Upstream oxygen sensor (arrow) -

V6 engine (front exhaust manifold) shown

IAT sensor is combined with the MAP sensor
into a single unit.

General description

The MAP sensor monitors the intake

manifold pressure changes resulting from
changes in engine load and speed and con-

verts the information into a voltage output.
The PCM uses the MAP sensor to control fuel

delivery and ignition timing. The PCM will
receive the information as a voltage signal

that will vary from approximately 1.5 to 2.1
volts at closed throttle (high vacuum) and 4.0
to 4.5 volts at wide open throttle (low vac-

uum). The MAP sensor is located on the
intake manifold (see illustrations 3.40a,

3.40b, and 3.40c).

Check

Refer to illustration 3.57

Note: To backprobe an electrical connector,

use pins or paper clips inserted into the rear
of the connector (or wire) to facilitate meter
attachment. Be careful not to let the probes
touch each other during this process.
57

First, check the MAP sensor supply volt-

age; disconnect the electrical connector and
turn the ignition key ON (engine OFF). Using a
voltmeter, check for voltage between the vio-

let/white wire (positive) and the black/light
blue wire (sensor ground) at the sensor con-
nector (see illustration). There should be

approximately 4 to 5 volts present. If no volt-
age is indicated, check for a blown fuse and
examine the wires for obvious damage. If the
circuit looks OK, have the PCM checked out
at your local dealer service department or
other qualified repair shop.
58

Next check the MAP sensor output volt-

age; reconnect the electrical connector to the
sensor and turn the ignition key ON (engine
OFF). Using a voltmeter, backprobe the
black/light blue wire (sensor ground) and the
dark green/red wire (MAP signal output -
positive) at the sensor connector. There
should be approximately 4 to 5 volts present.
If supply voltage is detected but there is no
signal voltage, replace the MAP sensor. Start

Chapter 6 Emissions and engine control systems

6-11

3.62b Downstream oxygen sensor (arrow)

the engine, the voltage should drop to
approximately 1.5 to 2.1 volts with the engine

idling. If the MAP sensor voltage readings are
incorrect, replace the MAP sensor.

Replacement

Disconnect the electrical connector

from the MAP sensor.

Remove the MAP sensor mounting bolts

and detach the sensor from the intake mani-

fold.

Installation is the reverse of removal.

Tighten the sensor bolts to the torque given

in this Chapter's Specifications.

Oxygen

sensor

General description

Refer to illustrations 3.62a and 3.62b
62

Four-cylinder engines are equipped with

t wo oxygen sensors, an upstream oxygen
sensor, which is located in the exhaust mani-
fold and a downstream oxygen sensor, which
is located at the outlet pipe of the catalytic
converter (see illustrations). On V6 engines,
there

are three oxygen sensors, two

upstream sensors - one located in each
exhaust manifold (front and rear) and one
located at the outlet pipe of the catalytic con-
verter. The upstream oxygen sensor(s) act as
a rich/lean switch indicating the air/fuel mix-
ture to the PCM which then adjusts the injec-
tor pulse width to obtain the ideal mixture
ratio of 14.7 parts of air to 1 part fuel. The
downstream oxygen sensor provides the

PCM with the same information as the

upstream sensor, but by comparing the data
from both sensors, the PCM can monitor cat-
alytic converter efficiency. The oxygen con-
tent in the exhaust reacts with the oxygen
sensor to produce a voltage output which
varies from 0.1 volt (high oxygen, lean mix-
ture) to 1.0 volts (low oxygen, rich mixture).
The sensors are equipped with a heating ele-

ment that keeps the them at proper operating

temperature during all operating modes.
63

The oxygen sensor produces no voltage

when it is below its normal operating temper-
ature of about 600 degrees F. During this ini-
tial period before warm-up, the PCM oper -

ates in the OPEN LOOP mode.
64

When there is a problem with the oxy-

gen sensor or its circuit, the PCM operates in
the open loop mode - that is, it controls fuel
delivery in accordance with a programmed
default value instead of feedback information
from the oxygen sensors.
65

The proper operation of the oxygen sen-

sors depends on four conditions:

a) Electrical - The low voltages generated

by the sensors depend upon good,
clean connections which should be
checked whenever a malfunction of the
sensor(s) is suspected or indicated.

b) Outside air supply - The sensors are

designed to allow air circulation to the
internal portion of the sensor. Whenever
the sensor is removed and installed or
replaced, make sure the air passages are
not restricted.

c) Proper operating temperature - The

PCM will not react to the sensor signal
until the sensor reaches approximately
600-degrees F. This factor must be
taken into consideration when evaluating
the performance of the sensor.

d) Unleaded fuel - The use of unleaded

fuel is essential for proper operation of
the sensors. Make sure the fuel you are
using is of this type.

66 In addition to observing the above con-

ditions, special care must be taken whenever

the sensor(s) is serviced.

a) The oxygen sensors have a permanently

attached pigtail and electrical connector

which should not be removed from the

sensor. Damage or removal of the pigtail

or electrical connector can adversely

affect operation of the sensor(s) and

engine.

b) Grease, dirt and other contaminants

should be kept away from the electrical

connector and the louvered end of the

sensor(s).

c) Do not use cleaning solvents of any kind

on the oxygen sensors.

d) Do not drop or roughly handle the sen-

sors.

Check

Raise the vehicle and support it securely

on jackstands.
68

Locate the oxygen sensor electrical

connector and disconnect it. Using a volt-
meter, check for battery supply voltage; con-
nect the positive probe to the dark
green/orange wire (or orange/dark green wire
depending on engine/year) and the black wire
at the connector terminal. Because the bat-
tery voltage is supplied to the sensor through
the ASD relay, voltage will only be supplied
for a very short time, approximately 4 sec-
onds. Have an assistant turn the ignition key
to the ON position (engine OFF) several
ti mes while you observe the voltmeter. The
voltmeter should jump up to battery voltage
each time the ignition is turned ON. If no volt-
age is indicated, check for a blown fuse and
examine the wires for obvious damage. If the

circuit looks OK, check the ASD relay (see
Chapter 4) and if necessary, have the PCM
checked out at your local dealer service
department or other qualified repair shop.
69

Next, check the sensor heater resis-

tance; using an ohmmeter, measure the
resistance between the two white wire termi-
nals of the sensor electrical connector. The
resistance should be approximately 4 to 7
ohms. If the resistance is not as specified,
replace the sensor.

Replacement

Refer to illustration 3.71

Note: Because they are installed in the

exhaust manifold and catalytic converter,
which contracts when cool, the oxygen sen-
sors may be very difficult to loosen when the
engine is cold. Rather than risk damage to the
sensor (assuming you are planning to reuse it
in another manifold or pipe), start and run the
engine for a minute or two, then shut it off. Be
careful not to burn yourself during the follow-
ing procedure.

Raise the vehicle and place it securely

on jackstands.
71

Carefully disconnect the electrical con-

nector from the sensor and unscrew the sen-
sor from the exhaust manifold or catalytic
converter (see illustration).
72 If the sensor is to be re-installed, apply
an anti-seize compound to the threads to

facilitate future removal. The threads of new

sensors are already coated with this com-
pound.
73 Install the sensor and tighten it to the
torque given in this Chapter's Specifications.
74

Reconnect the electrical connector of

the sensor lead to the engine wiring harness
and lower the vehicle.

PARK/NEUTRAL

position

switch

Refer to Chapter 7 for the Park/Neutral

position switch service procedures. A failure
in the PARK/NEUTRAL sensor circuit will set
a code 37 in the PCM memory.

3.71 Special sockets are available for

oxygen sensor removal; however, a

flare-nut wrench or crows foot works

just as well

6-12

Power steering pressure
switch

Turning the steering wheel increases the

power steering fluid pressure and the load
placed upon the engine by the power steer-
ing pump. The pressure switch will close
before the load causes an idle problem.
77

A pressure switch that will not open or

an open circuit from the PCM will cause the
ignition timing to retard at idle and this will
affect idle quality.
78

A pressure switch that will not close or

an open circuit may cause the engine to die

when the power steering system is used

heavily.
79

Any problems with the power steering

pressure switch or circuit should be diag-
nosed and repaired by a dealer service

department or other qualified repair shop.

Throttle Position Sensor (TPS)

General description

Refer to illustrations 3.80a and 3.80b
80

The Throttle Position Sensor (TPS) is

located on the end of the throttle shaft on the
throttle body (see illustrations). By monitor-
ing the output voltage from the TPS, the PCM
can determine fuel delivery based on throttle
valve angle (driver demand). A broken or
loose TPS can cause intermittent bursts of
fuel from the injectors and an unstable idle
because the PCM senses the throttle is mov-
ing.

Check

Note: To backprobe an electrical connector,

use pins or paper clips inserted into the rear
of the connector (or wire) to facilitate meter
attachment. Be careful not to short the
probes during this process.
81

First, check the TPS supply voltage; dis-

connect the electrical connector and turn the

ignition key ON (engine OFF). Using a volt-
meter, check for voltage between the vio-
let/white wire (positive) and the black/light
blue wire (ground) at the sensor connector.

There should be approximately 5 volts pre -

3.80a The throttle Position Sensor (TPS)

(arrow) is mounted on the throttle body -

2.0L four-cylinder engine shown,

2.4L similar

sent. If no voltage is indicated, check for a

blown fuse and examine the wires for obvi-

ous damage. If the circuit looks OK, have the

PCM checked out at your local dealer service

department or other qualified repair shop.
82

Next, connect the electrical connector

to the TPS. Using a voltmeter, backprobe the
orange/light blue wire (TPS signal - positive)
and the black/light blue wire (ground). Turn
the ignition key to the ON position (engine
OFF). With the throttle valve fully closed, the
voltmeter should indicate approximately 0.5
volts. Slowly open the throttle valve and
watch for a smooth increase in voltage as the
sensor travels from the closed to full position.
The voltage should increase to approximately
4 volts. If the readings are not as specified,
replace the TPS.

Replacement

Refer to illustration 3.85

Remove the throttle body from the

intake manifold (see Chapter 4).
84

Unscrew the mounting screws and

remove the TPS from the throttle body.

3.80b Throttle Position Sensor (TPS)

(arrow) - V6 engines

When installing the TPS, be sure to align

the socket locating tangs on the TPS with the
throttle shaft in the throttle body (see illus-
tration). When the TPS is installed correctly,

it must be rotated slightly clockwise to align

the screw holes. After installing the screws,
the throttle valve should be fully closed. If it's
open, remove the TPS and reposition it on
the shaft tangs.
86

Tighten the TPS screws securely.

The remaining installation steps are the

reverse of removal.

Vehicle Speed Sensor (VSS) -

manual transaxles only

General description

Refer to illustration 3.88
88

The Vehicle Speed Sensor (VSS) is

located on the transaxle near the left engine
mount (see illustration). This sensor is a per-
manent magnetic variable reluctance sensor
that produces a pulsing voltage whenever
vehicle speed is over 3 mph. These pulses
are translated by the PCM to determine vehi-
cle speed, distance traveled and, on models
equipped with cruise control, it governs the
speed control servo.

Chapter

Emissions

and engine

control

systems

3.85 When installing the TPS onto the throttle body, make sure

the socket tangs are on the proper side of the throttle valve shaft
blade (arrows). When installed correctly, the TPS must be rotated

slightly clockwise to align the screw holes

3.88 The Vehicle Speed Sensor (VSS) is located on the transaxle

near the left engine mount - manual transaxles only

Chapter 6 Emissions and engine control systems

6-13

4.3 Disconnecting one of the two

Powertrain Control Module (PCM)

40-pin connectors

4.4 PCM mounting screws

Check

Note: To backprobe an electrical connector,

use pins or paper clips inserted into the rear

of the connector (or wire) to facilitate meter

attachment. Be careful not to short the
probes during this process.

Raise the vehicle and support it securely

on jackstands.
90

First, check the VSS sensor supply volt-

age; place the transaxle in Neutral and turn

the ignition key ON (engine OFF). Using a
voltmeter, backprobe the orange/white wire

(1995 models) or orange wire (all other mod-
els) (positive) and ground the other probe to

the transaxle. There should be approximately

8 volts present. If no voltage is indicated,
check for a blown fuse and examine the wires

for obvious damage. If the circuit looks OK,

have the PCM checked out at your local
dealer service department or other qualified
repair shop.
91

Next check the VSS sensor output volt-

age; backprobe the black/light blue wire
(sensor ground) and the white/orange wire
(VSS signal output - positive) at the sensor
connector. The voltage should fluctuate
between 0 and 8 volts. If supply voltage is
detected but there is no signal voltage,
replace the VSS sensor.

Replacement

Raise the vehicle and support it securely

on jackstands.
93

Clean the area around the VSS to pre-

vent contaminating the transaxle.
94

Disconnect the electrical connector

from the VSS.
95

Remove the retaining bolt and lift the

VSS from the transaxle. Note: When remov-
ing the VSS make sure the drive gear comes
out along with the VSS. Should the drive gear
fall into the transaxle, retrieve it and install it
back onto the VSS.
96 Installation is the reverse of removal.
Tighten the VSS retaining bolt securely.

Powertrain Control Module

(PCM) - check and replacement

Caution: The PCM is an Electro-Static Dis-
charge (ESD) sensitive electronic device,
meaning a static electricity discharge from

your body could possibly damage internal

electrical components. Make sure to properly
ground yourself and the PCM before handling
it. Avoid touching the electrical terminals of
the PCM unless absolutely necessary.

Check

Note: Because of a Federally mandated
extended warranty which covers the OBD-ll
system components and because any owner-
induced damage to the PCM, the sensors
and/or the control devices may void the war-
ranty, it is not recommended to attempt diag-
nosis of, or replace the PCM at home while
the vehicle is under warranty.
1

The PCM requires special test equip -

ment to verify its integrity. Therefore, if the
PCM is suspected to be faulty, the vehicle

should be taken to your local dealer service
department or other qualified repair shop for
testing or repair.

Replacement

Refer to illustrations 4.3 and 4.4
2

Disconnect the negative battery cable

from the ground stud on the left shock tower

(see Chapter 5, Section 1).

The PCM is mounted to a bracket

between the air filter housing and the Power
Distribution Center (PDC). Disconnect both

40-pin connectors from the PCM (see illus-
tration).
4

Remove the PCM mounting screws (see

illustration) and withdraw it from the vehicle.
5

Installation is the reverse of removal.

Positive Crankcase Ventilation

(PCV) system - general
description

The Positive Crankcase Ventilation

(PCV) system reduces hydrocarbon exhaust
emissions by scavenging crankcase vapors.
This is accomplished by circulating fresh air
from the air cleaner through the crankcase,
where it mixes with blow-by gases and is
then re-routed through the PCV valve to the
intake manifold to be burned in the combus -

tion process.

The main components of the PCV sys-

tem are the PCV valve and the vacuum hoses
that connect it to the manifold.

To maintain idle quality, the PCV valve

restricts the flow when the intake manifold
vacuum is high. If abnormal operating condi-

tions (such as piston ring problems) arise, the

system is designed to allow excessive
amounts of blow-by gases to flow back

through the crankcase vent tube into the air

cleaner to be consumed by normal combus-

tion.
4

Check and replacement of the PCV

valve is performed in Chapter 1.

Exhaust Gas Recirculation (EGR)
system - description, check and
component replacement

Note: If the EGR valve control solenoid

becomes disconnected or damaged, the
electrical signal will be lost and the EGR valve

will

be open at all times during warm-up and

driving conditions. The symptoms will be
poor performance, rough idle and driveability

problems.

General description

Refer to illustrations 6.1a and 6.1b

The EGR system reduces oxides of

nitrogen (NOx) by recirculating exhaust gases

6.1a Typical four-cylinder

engine EGR valve, tube and

solenoid/transducer

VALVE

locations - 2.0L engine

shown, as viewed from rear

of engine

Content .. 20 21 22 23 ..