Chrysler PT Cruiser. Manual — part 990
INSTALLATION
(1) Install EVAP canister over bracket tabs (Fig.
19).
(2) Push canister back and into the bracket until
the spring clips snap over the edge of the canister
(Fig. 18).
(3) Install the push pin through the EVAP canister
and the bracket and into the fuel tank (Fig. 17).
(4) Install hoses and lines.
(5) Install the fuel tank and EVAP system, refer to
the Fuel Tank removal/installation section in the
Fuel Delivery section.
(6) Lower vehicle.
(7) Install the negative battery cable.
(8) Install the air cleaner lid, connect the inlet air
temperature sensor and makeup air hose.
(9) Fill fuel tank. Use the DRBIII
t scan tool to
pressurize the fuel system. Check for leaks.
Fig. 19 Bracket Tabs
1 - TABS
25 - 20
EVAPORATIVE EMISSIONS
PT
VAPOR CANISTER (Continued)
ON-BOARD DIAGNOSTICS
TABLE OF CONTENTS
page
page
TASK MANAGER
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TASK MANAGER
DESCRIPTION
The PCM is responsible for efficiently coordinating
the operation of all the emissions-related compo-
nents. The PCM is also responsible for determining if
the diagnostic systems are operating properly. The
software designed to carry out these responsibilities
is call the “Task Manager”.
OPERATION
The Task Manager determines when tests happen
and when functions occur. Many of the diagnostic
steps required by OBD II must be performed under
specific operating conditions. The Task Manager soft-
ware organizes and prioritizes the diagnostic proce-
dures. The job of the Task Manager is to determine if
conditions are appropriate for tests to be run, moni-
tor the parameters for a trip for each test, and record
the results of the test. Following are the responsibil-
ities of the Task Manager software:
• Test Sequence
• MIL Illumination
• Diagnostic Trouble Codes (DTCs)
• Trip Indicator
• Freeze Frame Data Storage
• Similar Conditions Window
Test Sequence
In many instances, emissions systems must fail
diagnostic tests more than once before the PCM illu-
minates the MIL. These tests are known as ’two trip
monitors.’ Other tests that turn the MIL lamp on
after a single failure are known as ’one trip moni-
tors.’ A trip is defined as ’start the vehicle and oper-
ate it to meet the criteria necessary to run the given
monitor.’
Many of the diagnostic tests must be performed
under certain operating conditions. However, there
are times when tests cannot be run because another
test is in progress (conflict), another test has failed
(pending) or the Task Manager has set a fault that
may cause a failure of the test (suspend).
• Pending
Under some situations the Task Manager will not
run a monitor if the MIL is illuminated and a fault is
stored from another monitor. In these situations, the
Task Manager postpones monitors pending resolu-
tion of the original fault. The Task Manager does not
run the test until the problem is remedied.
For example, when the MIL is illuminated for an
Oxygen Sensor fault, the Task Manager does not run
the Catalyst Monitor until the Oxygen Sensor fault is
remedied. Since the Catalyst Monitor is based on sig-
nals from the Oxygen Sensor, running the test would
produce inaccurate results.
• Conflict
There are situations when the Task Manager does
not run a test if another monitor is in progress. In
these situations, the effects of another monitor run-
ning could result in an erroneous failure. If this con-
flict is present, the monitor is not run until the
conflicting condition passes. Most likely the monitor
will run later after the conflicting monitor has
passed.
For example, if the Fuel System Monitor is in
progress, the Task Manager does not run the catalyst
Monitor. Since both tests monitor changes in air/fuel
ratio and adaptive fuel compensation, the monitors
will conflict with each other.
• Suspend
Occasionally the Task Manager may not allow a two
trip fault to mature. The Task Manager will sus-
pend the maturing of a fault if a condition exists
that may induce an erroneous failure. This prevents
illuminating the MIL for the wrong fault and allows
more precise diagnosis.
For example, if the PCM is storing a one trip fault
for the Oxygen Sensor and the catalyst monitor, the
Task Manager may still run the catalyst Monitor but
will suspend the results until the Oxygen Sensor
Monitor either passes or fails. At that point the Task
Manager can determine if the catalyst system is
actually failing or if an Oxygen Sensor is failing.
PT
ON-BOARD DIAGNOSTICS
25 - 21
MIL Illumination
The PCM Task Manager carries out the illumina-
tion of the MIL. The Task Manager triggers MIL illu-
mination upon test failure, depending on monitor
failure criteria.
The Task Manager Screen shows both a Requested
MIL state and an Actual MIL state. When the MIL is
illuminated upon completion of a test for a good trip,
the Requested MIL state changes to OFF. However,
the MIL remains illuminated until the next key
cycle. (On some vehicles, the MIL will actually turn
OFF during the thirdgood trip) During the key cycle
for the third good trip, the Requested MIL state is
OFF, while the Actual MIL state is ON. After the
next key cycle, the MIL is not illuminated and both
MIL states read OFF.
Diagnostic Trouble Codes (DTCs)
With OBD II, different DTC faults have different
priorities according to regulations. As a result, the
priorities determine MIL illumination and DTC era-
sure. DTCs are entered according to individual prior-
ity. DTCs with a higher priority overwrite lower
priority DTCs.
Priorities
• Priority 0 —Non-emissions related trouble codes.
• Priority 1 — One trip failure of a two trip fault
for non-fuel system and non-misfire. (MIL Off)
• Priority 2 — One trip failure of a two trip fault
for fuel system (rich/lean) or misfire. (MIL Off)
• Priority 3 — Two trip failure for a non-fuel sys-
tem and non-misfire or matured one trip comprehen-
sive component fault. (MIL On)
• Priority 4 — Two trip failure or matured fault
for fuel system (rich/lean) and misfire or one trip cat-
alyst damaging misfire. Catalyst damage misfire is a
2 trip MIL. The MIL flashes on the first trip when
catalyst damage misfire levels are present. (MIL On)
Non-emissions related failures have no priority.
One trip failures of two trip faults have low priority.
Two trip failures or matured faults have higher pri-
ority. One and two trip failures of fuel system and
misfire monitor take precedence over non-fuel system
and non-misfire failures.
DTC Self Erasure
With one trip components or systems, the MIL is
illuminated upon test failure and DTCs are stored.
Two trip monitors are components requiring failure
in two consecutive trips for MIL illumination. Upon
failure of the first test, the Task Manager enters a
maturing code. If the component fails the test for a
second time the code matures and a DTC is set.
After three good trips the MIL is extinguished and
the Task Manager automatically switches the trip
counter to a warm-up cycle counter. DTCs are auto-
matically erased following 40 warm-up cycles if the
component does not fail again.
For misfire and fuel system monitors, the compo-
nent must pass the test under a Similar Conditions
Window in order to record a good trip. A Similar Con-
ditions Window is when engine RPM is within ±375
RPM and load is within ±20% of when the fault
occurred.
NOTE: It is important to understand that a compo-
nent does not have to fail under a similar window of
operation to mature. It must pass the test under a
Similar Conditions Window when it failed to record
a Good Trip for DTC erasure for misfire and fuel
system monitors.
DTCs can be erased anytime with a DRBIII
t.
Erasing the DTC with the DRBIII
t erases all OBD II
information. The DRBIII
t automatically displays a
warning that erasing the DTC will also erase all
OBD II monitor data. This includes all counter infor-
mation for warm-up cycles, trips and Freeze Frame.
Trip Indicator
The Trip is essential for running monitors and
extinguishing the MIL. In OBD II terms, a trip is a
set of vehicle operating conditions that must be met
for a specific monitor to run. All trips begin with a
key cycle.
Good Trip
The Good Trip counters are as follows:
• Global Good Trip
• Fuel System Good Trip
• Misfire Good Trip
• Alternate Good Trip (appears as a Global Good
Trip on DRBIII
t)
• Comprehensive Components
• Major Monitor
• Warm-Up Cycles
Global Good Trip
To increment a Global Good Trip, the Oxygen sen-
sor and Catalyst efficiency monitors must have run
and passed, and 2 minutes of engine run time.
Fuel System Good Trip
To count a good trip (three required) and turn off
the MIL, the following conditions must occur:
• Engine in closed loop
• Operating in Similar Conditions Window
• Short Term multiplied by Long Term less than
threshold
• Less than threshold for a predetermined time
If all of the previous criteria are met, the PCM will
count a good trip (three required) and turn off the
MIL.
25 - 22
ON-BOARD DIAGNOSTICS
PT
TASK MANAGER (Continued)
Misfire Good Trip
If the following conditions are met the PCM will
count one good trip (three required) in order to turn
off the MIL:
• Operating in Similar Condition Window
• 1000 engine revolutions with no misfire
Alternate Good Trip
Alternate Good Trips are used in place of Global
Good Trips for Comprehensive Components and
Major Monitors. If the Task Manager cannot run a
Global Good Trip because a component fault is stop-
ping the monitor from running, it will attempt to
count an Alternate Good Trip.
The Task Manager counts an Alternate Good Trip
for Comprehensive components when the following
conditions are met:
• Two minutes of engine run time, idle or driving
• No other faults occur
The Task Manager counts an Alternate Good Trip
for a Major Monitor when the monitor runs and
passes. Only the Major Monitor that failed needs to
pass to count an Alternate Good Trip.
Warm-Up Cycles
Once the MIL has been extinguished by the Good
Trip Counter, the PCM automatically switches to a
Warm-Up Cycle Counter that can be viewed on the
DRBIII
t. Warm-Up Cycles are used to erase DTCs
and Freeze Frames. Forty Warm-Up cycles must
occur in order for the PCM to self-erase a DTC and
Freeze Frame. A Warm-Up Cycle is defined as fol-
lows:
• Engine coolant temperature must start below
and rise above 160° F
• Engine coolant temperature must rise by 40° F
• No further faults occur
Freeze Frame Data Storage
Once a failure occurs, the Task Manager records
several engine operating conditions and stores it in a
Freeze Frame. The Freeze Frame is considered one
frame of information taken by an on-board data
recorder. When a fault occurs, the PCM stores the
input data from various sensors so that technicians
can determine under what vehicle operating condi-
tions the failure occurred.
The data stored in Freeze Frame is usually
recorded when a system fails the first time for two
trip faults. Freeze Frame data will only be overwrit-
ten by a different fault with a higher priority.
CAUTION: Erasing DTCs, either with the DRBIII
T
; or
by disconnecting the battery, also clears all Freeze
Frame data.
Similar Conditions Window
The Similar Conditions Window displays informa-
tion about engine operation during a monitor. Abso-
lute MAP (engine load) and Engine RPM are stored
in this window when a failure occurs. There are two
different Similar conditions Windows: Fuel System
and Misfire.
FUEL SYSTEM
• Fuel System Similar Conditions Window —
An indicator that ’Absolute MAP When Fuel Sys Fail’
and ’RPM When Fuel Sys Failed’ are all in the same
range when the failure occurred. Indicated by switch-
ing from ’NO’ to ’YES’.
• Absolute MAP When Fuel Sys Fail — The
stored MAP reading at the time of failure. Informs
the user at what engine load the failure occurred.
• Absolute MAP — A live reading of engine load
to aid the user in accessing the Similar Conditions
Window.
• RPM When Fuel Sys Fail — The stored RPM
reading at the time of failure. Informs the user at
what engine RPM the failure occurred.
• Engine RPM — A live reading of engine RPM
to aid the user in accessing the Similar Conditions
Window.
• Adaptive Memory Factor — The PCM utilizes
both Short Term Compensation and Long Term Adap-
tive to calculate the Adaptive Memory Factor for
total fuel correction.
• Upstream O2S Volts — A live reading of the
Oxygen Sensor to indicate its performance. For
example, stuck lean, stuck rich, etc.
• SCW Time in Window (Similar Conditions
Window Time in Window) — A timer used by the
PCM that indicates that, after all Similar Conditions
have been met, if there has been enough good engine
running time in the SCW without failure detected.
This timer is used to increment a Good Trip.
• Fuel System Good Trip Counter — A Trip
Counter used to turn OFF the MIL for Fuel System
DTCs. To increment a Fuel System Good Trip, the
engine must be in the Similar Conditions Window,
Adaptive Memory Factor must be less than cali-
brated threshold and the Adaptive Memory Factor
must stay below that threshold for a calibrated
amount of time.
• Test Done This Trip — Indicates that the
monitor has already been run and completed during
the current trip.
MISFIRE
• Same Misfire Warm-Up State — Indicates if
the misfire occurred when the engine was warmed up
(above 160° F).
PT
ON-BOARD DIAGNOSTICS
25 - 23
TASK MANAGER (Continued)
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