DODGE TOWN AND COUNTRY 2001 Service Manual
Manufacturer: DODGE, Model Year: 2001, Model line: TOWN AND COUNTRY, Model: DODGE TOWN AND COUNTRY 2001Pages: 2321, PDF Size: 68.09 MB
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VAPOR CANISTER
DESCRIPTION
There are 2 EVAP canisters on the vehicle. The vac-
uum and vapor tubes connect to the top of the canister.
It is a charcoal canister (Fig. 11) or (Fig. 12).
OPERATION
All vehicles use a, maintenance free, evaporative
(EVAP) canister. Fuel tank vapors vent into the can-
ister. The canister temporarily holds the fuel vapors
until intake manifold vacuum draws them into the
combustion chamber. The Powertrain Control Module
(PCM) purges the canister through the proportional
purge solenoid. The PCM purges the canister at pre-
determined intervals and engine conditions.
Purge Free Cells
Purge-free memory cells are used to identify the
fuel vapor content of the evaporative canister. Since
the evaporative canister is not purged 100% of thetime, the PCM stores information about the evapora-
tive canister's vapor content in a memory cell.
The purge-free cells are constructed similar to cer-
tain purge-normal cells. The purge-free cells can be
monitored by the DRB IIItScan Tool. The only dif-
ference between the purge-free cells and normal
adaptive cells is that in purge-free, the purge is com-
pletely turned off. This gives the PCM the ability to
compare purge and purge-free operation.
REMOVAL
(1) Raise and support the vehicle.
(2) Remove the 2 hoses (Fig. 11).
(3) Remove bolt.
(4) Pull canister rearward to remove.
REMOVAL - REAR EVAP CANISTER
(1) Raise and support the vehicle.
(2) Remove 3 hoses (Fig. 12).
(3) Remove the bolt.
(4) Pull rearward to remove canister.
Fig. 11 FRONT EVAP CANISTER
1 - Front EVAP Canister
2 - Vent Valve
Fig. 12 REAR EVAP CANISTER
1 - Rear EVAP Canister
2 - Front EVAP Canister
3 - Vent Valve
25 - 18 EVAPORATIVE EMISSIONSRS
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INSTALLATION
(1) Install canister arrow heads into the rubber
gromments (Fig. 13)
(2) Install bolt and tighten.
(3) Install hoses.
(4) Lower vehicle.
INSTALLATION - REAR EVAP CANISTER
(1) Install canister arrow heads into the rubber
gromments (Fig. 14).
(2) Install bolt and tighten.
(3) Install hoses.
(4) Lower vehicle.
Fig. 13 FRONT EVAP CANISTER BRACKET
Fig. 14 REAR EVAP CANISTER BRACKET
RSEVAPORATIVE EMISSIONS25-19
VAPOR CANISTER (Continued)
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EXHAUST GAS RECIRCULATION
TABLE OF CONTENTS
page page
EXHAUST GAS RECIRCULATION
SPECIFICATIONS........................20
TUBE
REMOVAL..............................20
INSTALLATION...........................20VA LV E
DESCRIPTION...........................21
OPERATION.............................21
REMOVAL..............................22
INSTALLATION...........................22
EXHAUST GAS RECIRCULATION
SPECIFICATIONS
TORQUE
DESCRIPTION N´m Ft. Lbs. In. Lbs.
EGR valve to cyl. head 2.4L 22 200625
EGR tube to EGR valve 2.4L 11.9 105620
EGR tube to intake manifold 2.4L 11.9 105620
EGR valve to adaptor 3.3/3.8L 22 200625
EGR tube to EGR valve 3.3/3.8L 11.9 105620
EGR tube to intake manifold 3.3L 5.6 50610
EGR tube to intake manifold 3.8L 11.9 105620
TUBE
REMOVAL - 2.4L
(1) Remove EGR tube attaching bolts at intake
manifold.
(2) Remove EGR tube attaching bolts at EGR
valve.
(3) Check for signs of leakage or cracked surfaces
on either the manifold or tube. Repair or replace as
necessary.
REMOVAL - 3.3/3.8L
(1) Remove EGR tube attaching bolts at intake
manifold.
(2) Remove EGR tube attaching bolts at EGR
valve.
(3) Check for signs of leakage or cracked surfaces
on either the manifold or tube. Repair or replace as
necessary.
INSTALLATION - 2.4L
(1) Loose install EGR tube and gasket with attach-
ing bolts at intake manifold.
(2) Loose install EGR tube and gasket with attach-
ing bolts at EGR valve.
(3) Tighten bolts to EGR valve to 11.9 N´m (105
620 ins. lbs.).
(4) Tighten bolts to Intake manifold to 11.9 N´m
(105620 ins. lbs.).
INSTALLATION - 3.3L
(1) Loose install EGR tube with attaching screws
at intake manifold.
(2) Loose install EGR tube and gasket with attach-
ing bolts at EGR valve.
(3) Tighten bolts to EGR valve to 11.9 N´m (105
620 ins. lbs.).
(4) Tighten bolts to Intake manifold to 5.6 N´m (50
610 ins. lbs.).
25 - 20 EXHAUST GAS RECIRCULATIONRS
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NOTE: If you have a striped bolt at the Intake man-
ifold (Refer to 9 - ENGINE - STANDARD PROCE-
DURE) for thread repair.
INSTALLATION - 3.8L
(1) Loose install EGR tube and gasket with attach-
ing bolts at intake manifold.
(2) Loose install EGR tube and gasket with attach-
ing bolts at EGR valve.
(3) Tighten bolts to EGR valve to 11.9 N´m (105
620 ins. lbs.).
(4) Tighten bolts to Intake manifold to 11.9 N´m
(105620 ins. lbs.).
VA LV E
DESCRIPTION
The EGR system consists of:
²EGR tube (connects a passage in the intake
manifold to the exhaust port in the cylinder head)
²EGR valve
²Electronic EGR Transducer
²Connecting hoses
OPERATION
Refer to Monitored Systems - EGR Monitor in this
group for more information.
The engines use Exhaust Gas Recirculation (EGR)
systems. The EGR system reduces oxides of nitrogen
(NOx) in engine exhaust and helps prevent detona-
tion (engine knock). Under normal operating condi-tions, engine cylinder temperature can reach more
than 3000ÉF. Formation of NOx increases proportion-
ally with combustion temperature. To reduce the
emission of these oxides, the cylinder temperature
must be lowered. The system allows a predetermined
amount of hot exhaust gas to recirculate and dilute
the incoming air/fuel mixture. The diluted air/fuel
mixture reduces peak flame temperature during com-
bustion.
The electric EGR transducer contains an electri-
cally operated solenoid and a back-pressure trans-
ducer (Fig. 3). The Powertrain Control Module (PCM)
operates the solenoid. The PCM determines when to
energize the solenoid. Exhaust system back-pressure
controls the transducer.
When the PCM energizes the solenoid, vacuum
does not reach the transducer. Vacuum flows to the
transducer when the PCM de-energizes the solenoid.
When exhaust system back-pressure becomes high
enough, it fully closes a bleed valve in the trans-
ducer. When the PCM de-energizes the solenoid and
back-pressure closes the transducer bleed valve, vac-
uum flows through the transducer to operate the
EGR valve.
De-energizing the solenoid, but not fully closing the
transducer bleed hole (because of low back-pressure),
varies the strength of vacuum applied to the EGR
valve. Varying the strength of the vacuum changes
the amount of EGR supplied to the engine. This pro-
vides the correct amount of exhaust gas recirculation
for different operating conditions.
This system does not allow EGR at idle.
Fig. 1 EGR VALVE AND TUBE 2.4L
Fig. 2 EGR VALVE AND TUBE 3.3/3.8L
RSEXHAUST GAS RECIRCULATION25-21
TUBE (Continued)
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A failed or malfunctioning EGR system can cause
engine spark knock, sags or hesitation, rough idle,
engine stalling and increased emissions.
REMOVAL - 2.4L
The EGR valve and Electrical EGR Transducer are
serviced as an assembly (Fig. 1).(1) Disconnect vacuum tube from electric EGR
transducer. Inspect vacuum tube for damage.
(2) Remove electrical connector from solenoid.
(3) Remove EGR tube bolts from EGR valve.
(4) Remove EGR valve from cylinder head adaptor.
(5) Clean gasket surface and discard old gasket.
Check for any signs of leakage or cracked surfaces.
Repair or replace as necessary.
REMOVAL - 3.3/3.8L
The EGR valve and Electrical EGR Transducer are
serviced as an assembly (Fig. 2).
(1) Disconnect vacuum tube from electric EGR
transducer. Inspect vacuum tube for damage.
(2) Remove electrical connector from solenoid.
(3) Remove EGR tube bolts from EGR valve.
(4) Remove EGR valve from cylinder head adaptor.
(5) Clean gasket surface and discard old gasket.
Check for any signs of leakage or cracked surfaces.
Repair or replace as necessary.
INSTALLATION - 2.4L
The EGR valve and Electrical EGR Transducer are
serviced as an assembly (Fig. 1).
(1) Assemble EGR valve with new gasket onto the
cylinder head adaptor.
(2) Loose assemble the bolts from EGR valve to
EGR tube.
(3) Loose assemble the bolts from EGR valve to
cylinder head.
(4) Tighten bolts from EGR valve to cylinder head
to 22.8 N´m (200625 in. lbs.) torque.
(5) Tighten bolts from EGR valve to EGR tube to
11.9 N´m (105620 in. lbs.) torque.
(6) Reconnect vacuum hose and electrical connec-
tor to electrical EGR transducer.
INSTALLATION - 3.3/3.8L
The EGR valve and Electrical EGR Transducer are
serviced as an assembly (Fig. 2).
(1) Loose assemble the bolts from EGR valve to
EGR tube.
(2) Loose assemble the bolts from EGR valve to
cylinder head adaptor.
(3) Tighten bolts from EGR valve to EGR tube to
11.9 N´m (105620 in. lbs.) torque.
(4) Tighten bolts from EGR valve to cylinder head
to 22.9 N´m (200625 in. lbs.) torque.
(5) Reconnect vacuum hose and electrical connec-
tor to electrical EGR transducer.
Fig. 3 EGR Valve and Transducer - Typical
1 - DIAPHRAGM
2 - PISTON
3 - SPRING
4 - EGR VALVE ASSEMBLY
5 - VACUUM MOTOR
6 - VACUUM MOTOR FITTING
7 - VACUUM OUTLET FITTING TO EGR VALVE
8 - EGR VALVE CONTROL ASSEMBLY
9 - ELECTRIC SOLENOID PORTION OF VALVE CONTROL
10 - VACUUM INLET FITTING FROM ENGINE
11 - BACK-PRESSURE HOSE
12 - TRANSDUCER PORTION OF VALVE CONTROL
13 - ELECTRICAL CONNECTION POINT
14 - EGR VALVE BACK-PRESSURE FITTING
15 - EXHAUST GAS INLET
16 - STEM PROTECTOR AND BUSHING
17 - BASE
18 - MOVEMENT INDICATOR
19 - POPPET VALVE
20 - SEAT
21 - EXHAUST GAS OUTLET
25 - 22 EXHAUST GAS RECIRCULATIONRS
VALVE (Continued)
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ON-BOARD DIAGNOSTICS
TABLE OF CONTENTS
page page
TASK MANAGER
DESCRIPTION...........................23OPERATION.............................23
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 which tests happen
when and which functions occur when. Many of the
diagnostic steps required by OBD II must be per-
formed under specific operating conditions. The Task
Manager software organizes and prioritizes the diag-
nostic procedures. The job of the Task Manager is to
determine if conditions are appropriate for tests to be
run, monitor the parameters for a trip for each test,
and record the results of the test. Following are the
responsibilities of the Task Manager software:
²Test Sequence
²MIL Illumination
²Diagnostic Trouble Codes (DTCs)
²Trip Indicator
²Freeze Frame Data Storage
²Similar 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 know 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).
²Pending
Under some situations the Task Manager will notrun a monitor if the MIL is illuminated and a fault is
stored from another monitor. In these situations, the
Task Manager postpones monitorspendingresolu-
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.
²Conflict
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 thiscon-
flictis 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 EGR
Monitor. Since both tests monitor changes in air/fuel
ratio and adaptive fuel compensation, the monitors
will conflict with each other.
²Suspend
Occasionally the Task Manager may not allow a two
trip fault to mature. The Task Manager willsus-
pendthe 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 precis diagnosis.
For example, if the PCM is storing a one trip fault
for the Oxygen Sensor and the EGR monitor, the
Task Manager may still run the EGR 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 EGR system is actu-
ally failing or if an Oxygen Sensor is failing.
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.
RSON-BOARD DIAGNOSTICS25-23
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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 third 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 third key cycle) During the key cycle
for the third good trip, the Requested MIL state is
OFF, while the Actual MILL 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
²Priority 0 ÐNon-emissions related trouble codes
²Priority 1 Ð One trip failure of a two trip fault
for non-fuel system and non-misfire.
²Priority 2 Ð One trip failure of a two trip fault
for fuel system (rich/lean) or misfire.
²Priority3ÐTwotrip failure for a non-fuel sys-
tem and non-misfire or matured one trip comprehen-
sive component fault.
²Priority4ÐTwotrip failure or matured fault
for fuel system (rich/lean) and misfire or one trip cat-
alyst damaging misfire.
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 within6375RPM and load is within610% 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 DRBIIIt.
Erasing the DTC with the DRBIIIterases all OBD II
information. The DRBIIItautomatically 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
TheTripis 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:
²Global Good Trip
²Fuel System Good Trip
²Misfire Good Trip
²Alternate Good Trip (appears as a Global Good
Trip on DRBIIIt)
²Comprehensive Components
²Major Monitor
²Warm-Up Cycles
Global Good Trip
To increment a Global Good Trip, the Oxygen sen-
sor and Catalyst efficiency monitors must have run
and passed.
Fuel System Good Trip
To count a good trip (three required) and turn off
the MIL, the following conditions must occur:
²Engine in closed loop
²Operating in Similar Conditions Window
²Short Term multiplied by Long Term less than
threshold
²Less 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.
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:
²Operating in Similar Condition Window
²1000 engine revolutions with no misfire
Alternate Good Trip
Alternate Good Trips are used in place of Global
Good Trips for Comprehensive Components and
25 - 24 ON-BOARD DIAGNOSTICSRS
TASK MANAGER (Continued)
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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:
²Two minutes of engine run time
²No 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
DRBIIIt. 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:
²Engine coolant temperature must start below
and rise above 160É F
²Engine coolant temperature must rise by 40É F
²No 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 DRBIIIT;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
²Fuel System Similar Conditions WindowÐ
An indicator that 'Absolute MAP When Fuel Sys Fail'
and 'RPM When Fuel Sys Failed' are all in the samerange when the failure occurred. Indicated by switch-
ing from 'NO' to 'YES'.
²Absolute MAP When Fuel Sys FailÐ The
stored MAP reading at the time of failure. Informs
the user at what engine load the failure occurred.
²Absolute MAPÐ A live reading of engine load
to aid the user in accessing the Similar Conditions
Window.
²RPM When Fuel Sys FailÐ The stored RPM
reading at the time of failure. Informs the user at
what engine RPM the failure occurred.
²Engine RPMÐ A live reading of engine RPM
to aid the user in accessing the Similar Conditions
Window.
²Adaptive Memory FactorÐ The PCM utilizes
both Short Term Compensation and Long Term Adap-
tive to calculate the Adaptive Memory Factor for
total fuel correction.
²Upstream O2S VoltsÐ A live reading of the
Oxygen Sensor to indicate its performance. For
example, stuck lean, stuck rich, etc.
²SCW Time in Window (Similar Conditions
Window Time in Window)Ð 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.
²Fuel System Good Trip CounterÐATrip
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.
²Test Done This TripÐ Indicates that the
monitor has already been run and completed during
the current trip.
MISFIRE
²Same Misfire Warm-Up StateÐ Indicates if
the misfire occurred when the engine was warmed up
(above 160É F).
²In Similar Misfire WindowÐ An indicator
that 'Absolute MAP When Misfire Occurred' and
'RPM When Misfire Occurred' are all in the same
range when the failure occurred. Indicated by switch-
ing from 'NO' to 'YES'.
²Absolute MAP When Misfire OccurredÐ
The stored MAP reading at the time of failure.
Informs the user at what engine load the failure
occurred.
²Absolute MAPÐ A live reading of engine load
to aid the user in accessing the Similar Conditions
Window.
RSON-BOARD DIAGNOSTICS25-25
TASK MANAGER (Continued)
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Page 2309 of 2321
²RPM When Misfire OccurredÐ The stored
RPM reading at the time of failure. Informs the user
at what engine RPM the failure occurred.
²Engine RPMÐ A live reading of engine RPM
to aid the user in accessing the Similar Conditions
Window.
²Adaptive Memory FactorÐ The PCM utilizes
both Short Term Compensation and Long Term Adap-
tive to calculate the Adaptive Memory Factor for
total fuel correction.²200 Rev CounterÐ Counts 0±100 720 degree
cycles.
²SCW Cat 200 Rev CounterÐ Counts when in
similar conditions.
²SCW FTP 1000 Rev CounterÐ Counts 0±4
when in similar conditions.
²Misfire Good Trip CounterÐ Counts up to
three to turn OFF the MIL.
25 - 26 ON-BOARD DIAGNOSTICSRS
TASK MANAGER (Continued)
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EMISSIONS CONTROL 2.5L TURBO DIESEL
TABLE OF CONTENTS
page page
EMISSIONS CONTROL 2.5L TURBO DIESEL
DESCRIPTION............................1
SPECIFICATIONS.........................2EXHAUST GAS RECIRCULATION.............3
ON-BOARD DIAGNOSTICS..................6
EMISSIONS CONTROL 2.5L
TURBO DIESEL
DESCRIPTION
The 2.5L diesel Engine Control Module (ECM) con-
trols many different circuits in the fuel injection
pump and engine systems. If the ECM senses a prob-
lem with a monitored circuit that indicates an actual
problem, a Diagnostic Trouble Code (DTC) will be
stored in the ECM's memory, and eventually may
illuminate the MIL (Malfunction Indicator Lamp)
constantly while the key is on. If the problem is
repaired, or is intermittent, the ECM will erase the
DTC after 40 warm-up cycles without the the fault
detected. A warm-up cycle consists of starting the
vehicle when the engine is cold, then the engine is
warmed up to a certain temperature, and finally, the
engine temperature falls to a normal operating tem-
perature, then the key is turned off.
Certain criteria must be met for a DTC to be
entered into ECM memory. The criteria may be a
specific range of engine rpm, engine or fuel tempera-
ture and/or input voltage to the ECM. A DTC indi-
cates that the ECM has identified an abnormal
signal in a circuit or the system.
There are several operating conditions that the
ECM does not monitor and set a DTC for. Refer to
the following Monitored Circuits and Non±Monitored
Circuits in this section.
ECM MONITORED SYSTEMS
The ECM can detect certain problems in the elec-
trical system.
Open or Shorted Circuit± The ECM will not
distinguish between an open or a short to ground,
however the ECM can determine if there is excessive
current on a circuit, such as a short to voltage or a
decrease in component resistance.
Output Device Current Flow± The ECM senses
whether the output devices are electrically connected.
If there is a problem with the circuit, the ECM
senses whether the circuit is open, shorted to ground
(±), or shorted to (+) voltage.Fuel Pressure:Fuel pressure is controlled by the
fuel injection pump and fuel pressure solenoid. The
ECM uses a fuel pressure sensor to determine if a
fuel pressure problem exists.
Fuel Injector Malfunctions:The ECM can deter-
mine if a fuel injector has an electrical problem. The
fuel injectors on the diesel engine arecontrolledby
the ECM.
ECM NON±MONITORED SYSTEMS
The ECM does not monitor the following circuits,
systems or conditions that could have malfunctions
that result in driveability problems. A DTC will not
be displayed for these conditions.
Cylinder Compression:The ECM cannot detect
uneven, low, or high engine cylinder compression.
Exhaust System:The ECM cannot detect a
plugged, restricted or leaking exhaust system.
Vacuum Assist:Leaks or restrictions in the vac-
uum circuits of the Exhaust Gas Recirculation Sys-
tem (EGR) are not monitored by the ECM.
ECM System Ground:The ECM cannot deter-
mine a poor system ground. However, a DTC may be
generated as a result of this condition.
ECM/PCM Connector Engagement:The ECM
cannot determine spread or damaged connector pins.
However, a DTC may be generated as a result of this
condition.
HIGH AND LOW LIMITS
The ECM compares input signals from each input
device. It has high and low limits that are pro-
grammed into it for that device. If the inputs are not
within specifications and other DTC criteria are met,
a DTC will be stored in memory. Other DTC criteria
might include engine rpm limits or input voltages
from other sensors or switches. The other inputs
might have to be sensed by the ECM when it senses
a high or low input voltage from the control system
device in question.
RGEMISSIONS CONTROL 2.5L TURBO DIESEL25a-1
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