fuel consumption CHEVROLET DYNASTY 1993 Service Manual

CRANKCASE VENTILATION SYSTEM
Engine crankcase pressure and emissions are
vented into combustion chambers through the posi-
tive crankcase ventilation (PCV) system. The PCV
system consists of a crankcase filter (Fig. 6, 7, 8, 9,
or 10), PCV valve (Fig. 12, 13, 14 or 15) and hoses to
complete a vacuum circuit. The PCV system should
have enough volume to overcome crankcase pressure
created by piston backwash. If a PCV system be-
comes plugged, the crankcase pressure will increase
and force engine oil past the piston rings creating oil
consumption. Blockage of PCV system can occur at
the vacuum source coupling, PCV valve, crankcase
filter or a collapsed hose. Chrysler Corporation recommends that a PCV
valve not be cleaned. A new Mopar or equivalent
PCV valve should be installed when servicing is re-
quired. Over a period of time, depending on the en-
vironment where vehicle is used, deposits build up in
the PCV vacuum circuit. PCV system should be in-
spected at every oil change. Service PCV system if
engine oil is discharged into air cleaner.
Fig. 11 Cleaning Air Filter Element
Fig. 12 PCV SystemÐ3.0L Engine
Fig. 13 PCV SystemÐFlexible Fuel Engine
Fig. 14 PCV SystemÐ3.3L or 3.8L Engine
Fig. 15 PCV SystemÐ2.2L or 2.5L EFI Engine
Ä LUBRICATION AND MAINTENANCE 0 - 13

once the system has entered closed loop. Refer to
Modes of Operation in this section for an explanation
of closed loop operation.
NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems and conditions that could have malfunctions
that result in driveability problems. Diagnostic trou-
ble codes may not be displayed for these conditions.
However, problems with these systems may cause di-
agnostic trouble codes to be displayed for other sys-
tems. For example, a fuel pressure problem will not
register a fault directly, but could cause a rich or
lean condition. This could cause an oxygen sensor
fault to be stored in the PCM. Fuel Pressure - Fuel pressure is controlled by the
fuel pressure regulator. The PCM cannot detect a
clogged fuel pump inlet filter, clogged in-line fuel fil-
ter, or a pinched fuel supply or return line. However,
these could result in a rich or lean condition causing
an oxygen sensor fault. Secondary Ignition Circuit - The PCM cannot
detect an inoperative ignition coil, fouled or worn
spark plugs, ignition cross firing, or open spark plug
cables. Engine Timing - The PCM cannot detect an incor-
rectly indexed timing chain, camshaft sprocket and
crankshaft sprocket. The PCM also cannot detect an
incorrectly indexed distributor. However, these could
result in a rich or lean condition causing an oxygen
sensor fault to be stored in the PCM. Cylinder Compression - The PCM cannot detect
uneven, low, or high engine cylinder compression. Exhaust System
- The PCM cannot detect a
plugged, restricted or leaking exhaust system. Fuel Injector Malfunctions - The PCM cannot
determine if the fuel injector is clogged, the pintle is
sticking or the wrong injector is installed. However,
these could result in a rich or lean condition causing
an oxygen sensor fault to be stored in the PCM. Excessive Oil Consumption - Although the PCM
monitors the exhaust stream oxygen content through
the oxygen sensor when the system is in closed loop,
it cannot determine excessive oil consumption. Throttle Body Air Flow - The PCM cannot detect
a clogged or restricted air cleaner inlet or filter ele-
ment. Evaporative System - The PCM will not detect a
restricted, plugged or loaded evaporative purge can-
ister. Vacuum Assist - Leaks or restrictions in the vac-
uum circuits of vacuum assisted engine control sys-
tem devices are not monitored by the PCM. However,
these could result in a MAP sensor fault being stored
in the PCM. PCM System Ground - The PCM cannot deter-
mine a poor system ground. However, a diagnostic
trouble code may be generated as a result of this con-
dition. PCM Connector Engagement - The PCM cannot
determine spread or damaged connector pins. How-
ever, a diagnostic trouble code may be generated as a
result of this condition.
HIGH AND LOW LIMITS
The powertrain control module (PCM) compares in-
put signal voltages from each input device with es-
tablished high and low limits that are programmed
into it for that device. If the input voltage is not
within specifications and other diagnostic trouble
code criteria are met, a diagnostic trouble code will
be stored in memory. Other diagnostic trouble code
criteria might include engine RPM limits or input
voltages from other sensors or switches that must be
present before a fault condition can be verified.
DIAGNOSTIC TROUBLE CODE DESCRIPTION
When a diagnostic trouble code appears, it indi-
cates the powertrain control module (PCM) has rec-
ognized an abnormal condition in the system.
Diagnostic trouble codes can be obtained from the
malfunction indicator lamp (instrument panel Check
Engine lamp) on the Instrument Panel or from the
DRBII scan tool. Diagnostic trouble codes indicate
the results of a failure but do not identify the failed
component directly.
Fig. 3 Data Link Connector LocationÐAG and AJ Vehicles
14 - 42 FUEL SYSTEMS Ä

the PCM to store diagnostic trouble codes for other
systems. For example, a fuel pressure problem will not
register a fault directly, but could cause a rich or lean
condition. This could cause the PCM to store an oxygen
sensor diagnostic trouble code. Fuel Pressure - The vacuum assisted fuel pressure
regulator controls fuel system pressure. The PCM
cannot detect a clogged fuel pump inlet filter, clogged
in-line fuel filter, stuck open regulator, or a pinched
fuel supply or return line. However, these could result
in a rich or lean condition causing the PCM to store an
oxygen sensor diagnostic trouble code. Secondary Ignition Circuit - The PCM cannot
detect an inoperative ignition coil, fouled or worn spark
plugs, ignition cross firing, or open spark plug cables. Engine Timing - The PCM cannot detect an incor-
rectly indexed timing belt, camshaft sprocket and
crankshaft sprocket. However, these could result in a
rich or lean condition causing the PCM to store an
oxygen sensor diagnostic trouble code. Cylinder Compression - The PCM cannot detect
uneven, low, or high engine cylinder compression. Exhaust System - The PCM cannot detect a
plugged, restricted or leaking exhaust system. Fuel Injector Mechanical Malfunctions - The
PCM cannot determine if a fuel injector is clogged, the
needle is sticking or if the wrong injector is installed.
However, these could result in a rich or lean condition
causing the PCM to store an oxygen sensor diagnostic
trouble code. Excessive Oil Consumption - Although the PCM
monitors exhaust stream oxygen content when the
system is in closed loop, it cannot determine excessive
oil consumption. Throttle Body Air Flow - The PCM cannot detect a
clogged or restricted air cleaner inlet or filter element. Evaporative System - The PCM cannot detect a
disconnected (open vacuum line) restricted, plugged or
loaded evaporative purge canister. Vacuum Assist - The PCM cannot detect leaks or
restrictions in the vacuum circuits of vacuum assisted
engine control system devices. However, these could
cause the PCM to store a MAP sensor diagnostic
trouble code and cause a high idle condition. PCM System Ground - The PCM cannot determine
a poor system ground. However, one or more diagnostic
trouble codes may be generated as a result of this
condition. PCM Connector Engagement - The PCM may not
be able to determine spread or damaged connector
pins. However, it might store diagnostic trouble codes
as a result of spread connector pins.HIGH AND LOW LIMITS
The PCM compares input signal voltages from each
input device with established high and low limits for the
device. If the input voltage is not within limits and other
criteria are met, the PCM stores a diagnostic trouble code
in memory. Other diagnostic trouble code criteria might
include engine RPM limits or input voltages from other
sensors or switches that must be present before verifying
a diagnostic trouble code condition.
DIAGNOSTIC TROUBLE CODES
A diagnostic trouble code indicates the powertrain
control module (PCM) has recognized an abnormal
condition in the system. Abnormal conditions are usu-
ally shorted or open circuits.
The technician can display diagnostic trouble codes in
two ways. The first way is to cycle the ignition switch and
count the number of times the malfunction indicator lamp
(check engine lamp on the instrument panel) flashes on
and off. The DRBII scan tool provides the second method
of displaying diagnostic trouble codes. Diagnostic trouble
codes indicate the results of a circuit failure, but do not
directly identify the failed component.
For a list of Diagnostic Trouble Codes, refer to
the charts at the end of this section.
OBTAINING DIAGNOSTIC TROUBLE CODES
USING DRBII SCAN TOOL
WARNING: APPLY PARKING BRAKE AND/OR BLOCK
WHEELS BEFORE PERFORMING ANY TEST ON AN
OPERATING ENGINE. (1) Connect DRBII scan tool to the data link (diag-
nostic) connector located in the engine compartment,
next to the PCM (Fig. 1). (2) If possible, start the engine and cycle the A/C
switch if applicable. Shut off the engine. (3)
Turn the ignition switch on, access Read Fault
Screen. Record all the diagnostic trouble codes shown on
the DRBII scan tool. [Observe the malfunction indicator
lamp (check engine lamp) on the instrument panel. The
lamp should light for 2 seconds then go out (bulb check)].
To erase diagnostic trouble codes, use the Erase
Trouble Code data screen on the DRBII scan tool.
USING THE MALFUNCTION INDICATOR LAMP (1) Cycle the ignition key On - Off - On - Off - On
within 5 seconds. (2) Count the number of times the malfunction indi-
cator lamp (check engine lamp on the instrument
panel) flashes on and off. The number of flashes
represents the trouble code. There is a slight pause be-
Ä FUEL SYSTEMS 14 - 71

Secondary Ignition Circuit - The PCM cannot
detect an inoperative ignition coil, fouled or worn spark
plugs, ignition cross firing, or open spark plug cables. Engine Timing - The PCM cannot detect an incor-
rectly indexed timing chain, camshaft sprocket and
crankshaft sprocket. However, these could result in a
rich or lean condition causing an oxygen sensor fault. Cylinder Compression - The PCM cannot detect
uneven, low, or high engine cylinder compression. Exhaust System - The PCM cannot detect a
plugged, restricted or leaking exhaust system. Fuel Injector Malfunctions - The PCM cannot
determine if the fuel injector is clogged, the pintle is
sticking or the wrong injector is installed. However,
these could result in a rich or lean condition causing an
oxygen sensor fault to be stored in the PCM. Excessive Oil Consumption - Although the PCM
monitors exhaust stream oxygen content when the
system is in closed loop, it cannot determine excessive
oil consumption. Throttle Body Air Flow - The PCM cannot detect a
clogged or restricted air cleaner inlet or filter element. Evaporative System - The PCM will not detect a
restricted, plugged or loaded evaporative purge canis-
ter. Vacuum Assist - Leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices are not monitored by the PCM. How-
ever, these could result in a MAP sensor fault being
stored in the PCM. PCM System Ground
- The PCM cannot determine
a poor system ground. However, a diagnostic trouble
code may be generated as a result of this condition. PCM Connector Engagement - The PCM cannot
determine spread or damaged connector pins. How-
ever, a diagnostic trouble code may be generated as a
result of this condition.
HIGH AND LOW LIMITS
The powertrain control module (PCM) compares in-
put signal voltages from each input device with estab-
lished high and low limits that are programmed into it
for that device. If the input voltage is not within
specifications and other diagnostic trouble code criteria
are met, a diagnostic trouble code will be stored in
memory. Other diagnostic trouble code criteria might
include engine RPM limits or input voltages from other
sensors or switches that must be present before a fault
condition can be verified.
DIAGNOSTIC TROUBLE CODE DESCRIPTION
When a diagnostic trouble code appears, it indicates
the powertrain control module (PCM) has recognized
an abnormal condition in the system. Diagnostic
trouble codes can be obtained from the malfunction
indicator lamp (Check Engine lamp on the instrument
panel) or from the DRBII scan tool. Diagnostic trouble
codes indicate the results of a failure but do not
identify the failed component directly.
Ä FUEL SYSTEMS 14 - 101

NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems and conditions that could have malfunctions
that result in driveability problems. Diagnostic trouble
codes may not be displayed for these conditions. How-
ever, problems with these systems may cause diagnos-
tic trouble codes to be displayed for other systems. For
example, a fuel pressure problem will not register a
fault directly, but could cause a rich or lean condition.
This could cause an oxygen sensor fault to be stored in
the PCM. Fuel Pressure - Fuel pressure is controlled by the
vacuum assisted fuel pressure regulator. The PCM
cannot detect a clogged fuel pump inlet filter, clogged
in-line fuel filter, or a pinched fuel supply or return
line. However, these could result in a rich or lean
condition causing an oxygen sensor fault. Secondary Ignition Circuit - The PCM cannot
detect an inoperative ignition coil, fouled or worn spark
plugs, ignition cross firing, or open spark plug cables. Engine Timing - The PCM cannot detect an incor-
rectly indexed timing chain, camshaft sprocket and
crankshaft sprocket. The PCM also cannot detect an
incorrectly indexed distributor. However, these could
result in a rich or lean condition causing an oxygen
sensor fault to be stored in the PCM. Cylinder Compression - The PCM cannot detect
uneven, low, or high engine cylinder compression. Exhaust System - The PCM cannot detect a
plugged, restricted or leaking exhaust system. Fuel Injector Malfunctions
- The PCM cannot
determine if the fuel injector is clogged, the pintle is
sticking or the wrong injector is installed. However,
these could result in a rich or lean condition causing an
oxygen sensor fault to be stored in the PCM. Excessive Oil Consumption - Although the PCM
monitors exhaust stream oxygen content when the
system is in closed loop, it cannot determine excessive
oil consumption. Throttle Body Air Flow - The PCM cannot detect a
clogged or restricted air cleaner inlet or filter element. Evaporative System - The PCM will not detect a
restricted, plugged or loaded evaporative purge canis-
ter. Vacuum Assist - Leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices are not monitored by the PCM. How-
ever, these could result in a MAP sensor fault being
stored in the PCM. PCM System Ground - The PCM cannot determine
a poor system ground. However, a diagnostic trouble
code may be generated as a result of this condition. PCM Connector Engagement - The PCM cannot
determine spread or damaged connector pins. How-
ever, a diagnostic trouble code may be generated as a
result of this condition.
HIGH AND LOW LIMITS
The powertrain control module (PCM) compares in-
put signal voltages from each input device with estab-
lished high and low limits that are programmed into it
for that device. If the input voltage is not within
specifications, and other diagnostic trouble code crite-
ria are met, a diagnostic trouble code will be stored in
memory. Other diagnostic trouble code criteria might
include engine RPM limits or input voltages from other
sensors or switches that must be present before a fault
condition can be verified.
DIAGNOSTIC TROUBLE CODE DESCRIPTION
When a diagnostic trouble code appears, it indicates
that the Powertrain control module (PCM) has recog-
nized an abnormal condition in the system. Diagnostic
trouble codes can be obtained from the malfunction
indicator lamp (Check Engine lamp on the Instrument
Panel) or from the DRBII scan tool. Diagnostic trouble
codes indicate the results of a failure but do not
identify the failed component directly.
Fig. 3 PCMÐAG and AJ Bodies
Ä FUEL SYSTEMS 14 - 131

line. However, these could result in a rich or lean
condition causing an oxygen sensor fault to be stored in
the PCM. Secondary Ignition Circuit - The PCM cannot
detect an inoperative ignition coil, fouled or worn spark
plugs, ignition cross firing, or open spark plug cables. Engine Timing - The PCM cannot detect an incor-
rectly indexed timing chain, camshaft sprocket and
crankshaft sprocket. However, these could result in a
rich or lean condition causing an oxygen sensor fault to
be stored in the PCM. Cylinder Compression - The PCM cannot detect
uneven, low, or high engine cylinder compression. Exhaust System - The PCM cannot detect a
plugged, restricted or leaking exhaust system. Fuel Injector Malfunctions - The PCM cannot
determine if a fuel injector is clogged, the needle is
sticking or the wrong injector is installed. However,
these could result in a rich or lean condition causing an
oxygen sensor fault to be stored in the PCM. Excessive Oil Consumption - Although the PCM
monitors exhaust stream oxygen content when the
system is in closed loop, it cannot determine excessive
oil consumption. Throttle Body Air Flow - The PCM cannot detect a
clogged or restricted air cleaner inlet or filter element. Evaporative System - The PCM will not detect a
restricted, plugged or loaded evaporative purge canis-
ter. Vacuum Assist - Leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices are not monitored by the PCM. How-
ever, these could result in a MAP sensor fault being
stored in the PCM. PCM System Ground - The PCM cannot determine
a poor system ground. However, a diagnostic trouble
code may be generated as a result of this condition. PCM Connector Engagement - The PCM cannot
determine spread or damaged connector pins. How-
ever, a diagnostic trouble code may be generated as a
result of this condition.
HIGH AND LOW LIMITS
The powertrain control module (PCM) compares in-
put signal voltages from each input device with estab-
lished high and low limits for the device. If the input
voltage is not within limits and other diagnostic
trouble code criteria are met, a diagnostic trouble code
will be stored in memory. Other diagnostic trouble code
criteria might include engine RPM limits or input
voltages from other sensors or switches that must be
present before a fault condition can be verified.
DIAGNOSTIC TROUBLE CODE DESCRIPTION
A diagnostic trouble code indicates that the power-
train control module (PCM) has recognized an abnor- mal condition in the system. Diagnostic trouble codes
can be obtained from the malfunction indicator lamp
(Check Engine lamp on the instrument panel) or from
the DRBII scan tool. Diagnostic trouble codes indicate
the results of a failure but do not identify the failed
component directly.
SYSTEM TESTS
WARNING: APPLY PARKING BRAKE AND/OR BLOCK
WHEELS BEFORE PERFORMING ANY TEST ON AN
OPERATING ENGINE.
OBTAINING DIAGNOSTIC TROUBLE CODES
(1) Connect the DRBII scan tool to the data link
connector located in the engine compartment near the
driver side strut tower (Fig. 1). (2) Start the engine if possible, cycle the transaxle
selector and the A/Cswitch if applicable. Shut off the
engine. (3) Turn the ignition switch on, access Read Fault
Screen. Record all the fault messages shown on the
DRBII scan tool. Observe the malfunction indicator
lamp (check engine lamp on the instrument panel). The
lamp should light for 2 seconds then go out (bulb
check). Diagnostic trouble code erasure; access erase
diagnostic trouble code data
STATE DISPLAY TEST MODE
The switch inputs used by the powertrain control
module (PCM) have only two recognized states, HIGH
and LOW. For this reason, the PCM cannot recognize
the difference between a selected switch position ver-
sus an open circuit, a short circuit, or a defective
switch. If the change is displayed, it can be assumed
that the entire switch circuit to the PCM is functional.
From the state display screen access either State
Display Inputs and Outputs or State Display Sensors.
STATE DISPLAY INPUTS AND OUTPUTS
Connect the DRBII scan tool to the vehicle and access
the State Display screen. Then access Inputs and
Outputs. The following is a list of the engine control
system functions accessible through the Inputs and
Outputs screen. Park/Neutral Switch
Speed Control Resume
Brake Switch
Speed Control On/Off
Speed Control Set
A/C Switch Sense
S/C Vent Solenoid
Ä FUEL SYSTEMS 14 - 163