Chrysler PT Cruiser. Manual - part 228

3.2

FUNCTIONAL OPERATION

3.2.1

FUEL CONTROL

The PCM controls the air/fuel ratio of the engine

by varying fuel injector on time. Mass air flow is
calculated using the speed density method using
enigne speed, manifold absolute pressure, and air
temperature change.

Different fuel calculation strategies are used de-

pending on the operational state of the engine.
During crank mode, a longer pulse width fuel pulse
is delivered followed by fuel pulses determined by a
crank time strategy. Cold engine operation is deter-
mined via an open loop strategy until the O2
sensors have reached operating temperature. At
this point, the strategy enters a closed loop mode
where fuel requirements are based upon the state of
the O2 sensors, engine speed, MAP, throttle posi-
tion, air temperature, battery voltage, and coolant
temperature.

3.2.2

ON-BOARD DIAGNOSTICS

The PCM has been programmed to monitor many

different circuits of the fuel injection system. This
monitoring is called on-board diagnosis.

Certain criteria, or arming conditions, must be

met for a trouble code to be entered into the PCM
memory. The criteria may be a range of: engine rpm,
engine temperature, and/or input voltage to the
PCM. If a problem is sensed with a monitored
circuit, and all of the criteria or arming conditions
are met then a trouble code will be stored in the
PCM.

It is possible that a trouble code for a monitored

circuit may not be entered into the PCM memory
even though a malfunction has occurred. This may
happen because one of the trouble code criteria have
not been met.

The PCM compares input signal voltages from

each input device with specifications (the estab-
lished high and low limits of the range) that are
programmed into it for that device. If the input

voltage is not within specifications and other trou-
ble code criteria are met, a trouble code will be
stored in the PCM memory.

The On Board Diagnostics have evolved to the

second Generation of Diagnostics referred to as
OBDII/Euro Stage III OBD. These OBDII/Euro
Stage III OBD Diagnostics control the functions
necessary to meet the requirements of California
OBDII, Federal OBD regulation and European reg-
ulation. These requirements specify the inclusion of
a Malfunction Indicator Light (MIL) located on the
instrument panel. The purpose of the MIL is to
inform the vehicle operator in the event of a mal-
function of any emission system or component fail-
ure.

MIL Lamp Strategy
I/M Readiness OK to test = Key On Engine OFF

– MIL Lamp will remain on until the vehicle is
started or Ignition is turned off.

I/M not ready for testing = Key On Engine OFF

– MIL Lamp on solid for (15) seconds then MIL
Lamp will flash on/off for (5) seconds then it will
remain on until the vehicle is started or the Ignition
is turned off.

GENERAL INFORMATION

OBD II/EURO STAGE III OBD MONITOR INFORMATION

Comprehensive

Major Monitors

Components

Non Fuel Control

Fuel Control

Monitor

& Non Misfire

& Misfire

Run constantly

Run Once Per Trip

Run Constantly

Includes All Engine Hardware

Monitors Entire Emission

Monitors Entire System

- Sensors, Switches,

System

Solenoids, etc.

One Trip Faults - Turns On

Two Trip Faults - Turns On

The MIL and Sets DTC After

One Failure

Two Consecutive Failures

Priority 3

Priority 1 or 3

Priority 2 or 4

All Checked For Continuity

Done Stop Testing = Yes

Fuel Control Monitor

Open

Monitors Fuel Control

Short To Ground

Oxygen Sensor Heater

System For:

Short To Voltage

Oxygen Sensor Response

Fuel System Lean
Fuel System Rich

Inputs Checked For

Requires 3 Consecutive

Rationality

Catalytic Converter

Fuel System Good Trips

Efficiency Except EWMA

Extinguish The MIL

Outputs Checked For

- up to 6 tests per trip

Functionality

and a one trip fault

Misfire Monitor

Evaporative Emission

Monitors For Engine Misfire

System

at:

1000 RPM Counter

(Type B)

**200 RPM Counter

(Type A)

Requires 3 Consecutive

Global/Alternate Good Trips

Global Good Trips

Misfire Good Trips

to Extinguish the MIL*

To Extinguish the MIL

*40 Warm Up Cycles are required to erase

**Type A misfire is a two

DTC’s

after

the MIL has been extinguished.

trip failure. The MIL will
illuminate and blink at
the first failure.

GENERAL INFORMATION

OBDII Monitor Run Process
NGC Vehicle

The following procedure has been established to

assist Technicians in the field with enabling and
running OBDII Monitors. The order listed in the
following procedure is intended to allow the techni-
cian to effectively complete each monitor and to set
the CARB Readiness Status in the least time pos-
sible.

**NOTE**

A. Once the monitor run process has begun, do

not turn off the ignition. By turning the igni-
tion key off, monitor enabling conditions will
be lost. Only the 02 Heater Monitor runs after
key off.

B. By performing a Battery Disconnect, or Se-

lecting Erase DTCs, the CARB Readiness and
all

additional

OBD

information

will

cleared.

Monitor Preliminary Checks:

1. Plug a DRBIII into the vehicle’s DLC.

2. Turn the ignition, KEY ON–ENGINE OFF.

Watch for MIL lamp illumination during the
bulb check. MIL lamp must have illuminated, if
not, repair MIL lamp.

3. Press YES to agree to the License Agreement.

4. On the DRB III Select #1 DRB III Standalone.

5. Select #1 1998-2005 Diagnostics

6. Select #1 ALL (Except Below)

7. Select #1 Engine

8. Select #2 DTCs and Related Functions

9. Select #1 Read DTCs

*Verify that No Emissions Related DTCs are
Present.
*If an Emissions DTC is Present, the OBD II
Monitors may not run and the CARB Readiness
will not update.
*The Emissions related DTC, will need to be
repaired, then cleared. By clearing DTCs, the
OBD Monitors will need to be run and completed
to set the CARB Readiness Status.

10. Return to Engine Select Function Menu and

Select #9, OBD II Monitors.

11. Select #2 CARB Readiness Status.

Do all the CARB Readiness Status Locations read
YES?

*YES, then all monitors have been completed and
this vehicle is ready to be I/M or Emission Tested.
*NO, then the following procedure needs to be
followed to run/complete all available monitors.

**NOTE**
A. Only the monitors, which are not YES in the

CARB Readiness Status, need to be completed.

B. Specific criteria need to be met for each monitor.

Each monitor has a Pre-Test screen to assist in
running the monitor. For additional informa-
tion, refer to the Chrysler Corporation Technical
Training Workbook title On Board Diagnostics,
part number 81-699-97094.

The most efficient order to run the monitors has
been outlined below, including suggestions to aid
the process.

A. NATURAL VACUUM LEAK DETECTION WITH
PURGE MONITOR

This monitor requires a cool down cycle, usually

an overnight soak for at least 8 hours without the
engine running. The ambient temperature must
decrease overnight – parking the vehicle outside is
advised. To run this test the fuel level must be
between 15-85% full. For the monitor run condi-
tions select the EVAP MON PRE-TEST in the
DRB III

t, OBD II Monitors Menu. The Purge mon-

itor will run if the small leak test reports a pass.
Criteria for NVLD monitor:

1. Engine off time greater than one hour

2. Fuel Level between 15% and 85%

3. Start Up ECT and IAT within 10°C (18°F).

4. Vehicle started and run until Purge Monitor

reports a result.

NOTE: If the vehicle does not report a result
and the conditions were correct, it may take
up to two weeks to fail the small leak monitor.
DO NOT use this test to attempt to determine
a

fault.

Use

the

appropriate

service

information procedure for finding a small
leak. If there are no faults and the conditions
are correct this test will run and report a
pass. Note: The Small leak test can find leaks
less than 10 thousandths of an inch. If a
small leak is present, it takes approximately
one week of normal driving to report a failure.

B. CATALYST/O2 MONITOR

With NGC, Catalyst and O2 Monitor information

are acquired and processed at the same time. Most
vehicles will need to be driven at highway speed
(<50 mph) for a few minutes. Some trucks run the
monitor at idle in drive. If the vehicle is equipped
with a manual transmission, using 4

gear may

assist in meeting the monitor running criteria. For
the monitor run conditions, select the BANK 1 CAT
MON PRE-TEST in the DRB III

t, OBD II Monitors

Menu.

C. EGR MONITOR

The EGR monitor now runs in a closed throttle

decel or at idle on a warm vehicle. However, it is

GENERAL INFORMATION

necessary to maintain the TPS, Map and RPM
ranges to allow the monitor to complete itself. For
the monitor run conditions, select the EGR PRE-
TEST in the DRB III

t, OBD II Monitors Menu.

D. 02 SENSOR HEATER MONITOR

This monitor is now continuously running once

the heaters are energized. Pass information will be
processed at power down. For the monitor run
conditions, select the O2S HEATER MON PRE-
TEST in the DRB III

t, OBD II Monitors Menu.

3.2.3

OTHER CONTROLS

CHARGING SYSTEM (NGC)

The charging system is turned on when the

engine is started. The Generator field is controlled
by the PCM using a 12-volt high-side driver and a
body ground circuit. The Generator output voltage
is determined by the PCM. When more system
voltage is needed, the PCM will applies a longer
duty cycle using the 12-volt high-side drive and
shortens duty cycle or none at all when less voltage
is needed.

O2 SENSOR (NGC)

The O2 system with ignition on and engine off

has a normalized O2 voltage of around 5 volts as
displayed on the DRBIII or measured with a high
impedance voltmeter. As the O2 sensor starts gen-
erating a signal the voltage will move towards 2.5
volts. The voltage will typically vary between 2.5
volts and 3.5 volts on a normal running engine. The
goal voltage is also typically between 2.5 and 3.5
volts. This implies that the 0-volt through 1-volt
range that you are used to is still valid, only it is
shifted up by a 2.5 volt offset. This 2.5 volt supply is
being delivered through the sensor return line.

SPEED CONTROL SYSTEM

The PCM controls vehicle speed by operation of

the speed control servo vacuum and vent solenoids.
Energizing the vacuum solenoid applies vacuum to
the servo to increase throttle position. Operation of
the vent solenoid slowly releases the vacuum allow-
ing throttle position to decrease. A special vacuum
dump solenoid allows immediate release of the
throttle during speed control operation.

Speed control may be cancelled by braking, driver

input using the speed control switches, shifting into
neutral, excessive engine speed (wheels spinning),
or turning the ignition off.

NOTE: If two speed control switches are
selected simultaneously, the PCM will detect
an illegal switch operation and turn the speed
control off.

TURBOCHARGER SYSTEM 2.4L (NCG)

The turbocharger is a performance part and must

not be tampered with. The wastegate bracket is an
integral part of the turbocharger. Tampering with
the wastegate components can reduce durability by
increasing cylinder pressure and thermal loading
due to incorrect inlet and exhaust manifold pres-
sure. Poor fuel economy and failure to meet regula-
tory emissions laws may also result. Increasing the
turbocharger boost WILL NOT increase engine
power. The turbocharger is an exhaust-driven su-
percharger, which increases the pressure and den-
sity of the air entering the engine. With the increase
of air entering the engine, more fuel can be injected
into the cylinders, which creates more power during
combusion. Refer to the Service Manual informa-
tion for description and operation of the Turbo
system. The Turbo system consists of the following
components.

•

Turbocharger with Surge Valve and Wastegate
Actuators

•

Surge Valve Solenoid

•

Throttle Inlet Pressure (TIP) Solenoid

•

Wastegate Solenoid

•

Throttle Inlet Pressure (TIP) Sensor

NATURAL VACUUM LEAK DETECTION (NVLD)
(NGC)

The Natural Vacuum Leak Detection (NVLD)

system is the next generation evaporative leak
detection system that is used on vehicles equipped
with the latest Powertrain Control Module (PCM),
the Next Generation Controller (NGC) starting in
2002 M.Y. This new system replaces the leak detec-

GENERAL INFORMATION

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