lock CHEVROLET DYNASTY 1993 Service Manual

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

(3) Remove idle air control motor mounting screws.
(4) Remove idle air control motor from throttle
body (make certain that the O-ring is on motor).
INSTALLATION
(1) New idle air control motors have a new O-ring
installed on them. If pintle measures more than 1
inch (25 mm) it must be retracted. Use the IDLE
AIR CONTROL MOTOR OPEN/CLOSE mode of the
DRBII scan tool (battery must be reconnected for this
operation). (2) Carefully place idle air control motor into
throttle body. (3) Install 2 mounting screws. Tighten screws to 2
N Im (17 in. lbs.) torque.
(4) Connect harness connector to motor.
(5) Connect negative cable to battery.
THROTTLE BODY REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove clamp from air hose. Remove hose (Fig.
1). (3) Remove accelerator cable.
(4) Disconnect idle air control motor and throttle
position sensor (TPS) electrical connectors. (5) Remove throttle body mounting nuts.
(6) Remove throttle body and gasket.
(7) Reverse the above procedures for installation.
FUEL INJECTOR RAIL ASSEMBLY
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
WHEN SERVICING FLEXIBLE FUEL VEHICLES,
WEAR METHANOL RESISTANT GLOVES AND EYE
PROTECTION AND AVOID BREATHING FUMES. DO
NOT ALLOW METHANOL/GASOLINE MIXTURES TO
CONTACT SKIN. SERVICE VEHICLES IN WELL VEN-
TILATED AREAS AND AVOID IGNITION SOURCES.
NEVER SMOKE WHILE SERVICING THE VEHICLE.
REMOVAL
(1) Perform fuel system pressure release procedure.
(2) Disconnect negative cable from battery.
(3) Disconnect the fuel injector harness connector
from the engine harness (Fig. 6).
(4) Remove the quick connect fittings from the
chassis fuel tubes. Refer to Quick Connect Fittings in
the Fuel Delivery section of this group. (5) Disconnect the vacuum hose from the top of the
intake manifold (Fig. 6). (6) Disconnect vacuum hose from the pressure reg-
ulator (Fig. 6). (7) Remove screw from the fuel tube clamp (Fig.
6). (8) Remove fuel rail mounting screws.
(9) Pull up on the injector rail. The injectors will
pull straight out of the ports. Do not damage the in-
jector O-rings. (10) Remove fuel rail assembly from vehicle. Do
not remove fuel injectors until fuel rail assembly has
been completely removed from vehicle. (11) Plug or cover intake manifold injector ports to
prevent dirt from entering the openings (Fig. 7).
INSTALLATION
WARNING: FUEL RAILS, INJECTORS AND PRES-
SURE REGULATORS DESIGNED FOR GASOLINE
ONLY VEHICLES CANNOT BE USED ON FLEXIBLE
FUEL AA-BODY VEHICLES. WHEN SERVICING THE
FUEL SYSTEM OF A FLEXIBLE FUEL VEHICLE,
ONLY USE ORIGINAL EQUIPMENT OR EQUIVA-
LENT REPLACEMENT COMPONENTS.
(1) Ensure injectors are seated into the receiver
cup on the fuel rail with the lock ring in place. (2) Attach harness connectors to injectors. Fasten
the harness into wiring clips.
Fig. 5 Servicing Idle Air Control Motor
Fig. 6 Injector Harness and Engine Harness Connection
Ä FUEL SYSTEMS 14 - 79

(3) Ensure the injector holes are clean and all plugs
have been removed. (4) Lubricate the injector O-rings with a drop of
clean engine oil to ease installation. (5) Install the injector assembly into their holes.
Install mounting screws. Fuel rail assembly must be
drawn into the intake manifold evenly making sure
each injector enters its own hole. Once all injectors are
seated, tighten bolts to 23 N Im (200 in. lbs) torque.
(6) Connect vacuum hose to fuel pressure regulator.
(7) Close fuel tube clip around fuel tubes and install
fastener. (8) Lubricate the ends of the chassis fuel tubes with
a light coating of clean 30 weight engine oil. Connect
fuel supply and return hoses to chassis fuel tube
assembly. Pull back on the quick connect fittings to
ensure complete insertion. Refer to Quick Connect
Fittings in the Fuel Delivery section of this group. (9) Connect vacuum hose intake manifold nipple.
(10) Connect negative cable to battery.
CAUTION: When using the ASD Fuel System Test, the
Auto Shutdown (ASD) Relay remains energized for
either 7 minutes, until the test is stopped, or until the
ignition switch is turned to the Off position.
(11) With the DRBII scan tool, use the ASD Fuel
System Test to pressurize system and check for leaks.
FUEL INJECTOR
The fuel rail must be removed to service the injec-
tors. Refer to Fuel Injector Rail Assembly in this
section.
REMOVAL
WARNING: RELEASE FUEL SYSTEM PRESSURE BE-
FORE SERVICING FUEL SYSTEM COMPONENTS.
WHEN SERVICING FLEXIBLE FUEL VEHICLES,
WEAR METHANOL RESISTANT GLOVES AND EYE
PROTECTION AND AVOID BREATHING FUMES. DO NOT ALLOW METHANOL/GASOLINE MIXTURES TO
CONTACT SKIN. SERVICE VEHICLES IN WELL VEN-
TILATED AREAS AND AVOID IGNITION SOURCES.
NEVER SMOKE WHILE SERVICING THE VEHICLE.
(1) Disconnect electrical connector from injector
(Fig. 8).
(2) Position fuel rail assembly so that the fuel injec-
tors are easily accessible (Fig. 9). (3) Remove injector lock ring from fuel rail and
injector. Pull injector straight out of fuel rail receiver
cup. (4) Check injector O-ring for damage. Replace dam-
aged O-rings. If injector is reused, install a protective
cap on the injector tip to prevent damage. (5) Repeat steps for remaining injectors.
INSTALLATION
WARNING: FUEL INJECTORS AND INJECTOR
O-RINGS DESIGNED FOR GASOLINE ONLY VE-
HICLES CANNOT BE USED ON FLEXIBLE FUEL AA-
BODY VEHICLES. WHEN SERVICING THE FUEL SYS-
TEM OF A FLEXIBLE FUEL VEHICLE, ONLY USE
ORIGINAL EQUIPMENT OR EQUIVALENT REPLACE-
MENT COMPONENTS.
Fig. 7 Fuel Injector Ports
Fig. 8 Servicing Fuel Injectors
14 - 80 FUEL SYSTEMS Ä

(1) Before installing an injector, lubricate O-ring
with a drop of clean engine oil. (2) Being careful not to damage the O-ring, install
injector top end into fuel rail receiver cup. (3) Install injector lock ring by sliding open end
into slot of the injector and onto the receiver cup
ridge into the side slots of ring (Fig. 8). (4) Repeat steps for remaining injectors.
(5) Install injector wiring harness to injectors and
fasten into wiring clips (Fig. 10).
FUEL PRESSURE REGULATOR
WARNING: RELEASE FUEL SYSTEM PRESSURE
BEFORE SERVICING FUEL SYSTEM COMPONENTS.
WHEN SERVICING FLEXIBLE FUEL VEHICLES,
WEAR METHANOL RESISTANT GLOVES AND EYE PROTECTION AND AVOID BREATHING FUMES. DO
NOT ALLOW METHANOL/GASOLINE MIXTURES TO
CONTACT SKIN. SERVICE VEHICLES IN WELL VEN-
TILATED AREAS AND AVOID IGNITION SOURCES.
NEVER SMOKE WHILE SERVICING THE VEHICLE.
REMOVAL
(1) Perform fuel system pressure release procedure.
(2) Disconnect negative cable from battery.
(3) Disconnect vacuum hose from fuel pressure reg-
ulator (Fig. 11).
Place a shop towel under fuel pressure regula-
tor to absorb any fuel spillage. (4) Use 2 tubing wrenches, to loosen the line nut
on the fuel return tube (Fig. 12).
(5) Remove fuel pressure regulator mounting nuts
(Fig. 11). (6) Lift pressure regulator up out of fuel rail (Fig.
13). Ensure the O-ring and spacer were removed
with the regulator. Discard O-Ring.
Fig. 9 Fuel Rail and Injector Assembly
Fig. 10 Fuel Rail Assembly
Fig. 11 Servicing Fuel Pressure Regulator
Fig. 12 Removing Fuel Return Tube
Ä FUEL SYSTEMS 14 - 81

THROTTLE BODY
The throttle body assembly is located on the left
end of the intake manifold plenum (Fig. 20). The
throttle body houses the throttle position sensor and
the idle air control motor. Air flow through the throt-
tle body is controlled by a cable operated throttle
blade located in the base of the throttle body.
FUEL SUPPLY CIRCUIT
Fuel is pumped to the fuel rail by an electrical
pump in the fuel tank. The pump inlet is fitted with
a strainer to prevent water and other contaminants
from entering the fuel supply circuit. Fuel pressure is controlled to a preset level above
intake manifold pressure by a pressure regulator.
The regulator is mounted on the fuel rail (Fig. 21).
The regulator uses intake manifold pressure as a ref-
erence.
FUEL INJECTORS AND FUEL RAIL ASSEMBLY
Four fuel injectors are retained in the fuel rail by
lock rings. The rail and injector assembly are in-
stalled with the injectors inserted into recessed holes
in the intake manifold.
FUEL PRESSURE REGULATOR
The pressure regulator is a mechanical device lo-
cated on the fuel rail, downstream of the fuel injec-
tors (Fig. 22). The regulator maintains a constant
380 kPa (55 psi) across the fuel injector tip. The regulator contains a spring loaded rubber dia-
phragm that covers the fuel return port. When the
fuel pump is operating, fuel flows past the injectors
into the regulator, and is restricted from flowing any
further by the blocked return port. When fuel pres-
sure reaches 380 kPa (55 psi) it pushes on the dia-
phragm, compresses the spring, and uncovers the
fuel return port. The diaphragm and spring con-
stantly move from an open to closed position to keep
the fuel pressure constant.
Fig. 21 Fuel Supply Circuit
Fig. 22 Fuel Pressure Regulator
14 - 94 FUEL SYSTEMS Ä

SYSTEM TESTS
Apply parking brake and/or block wheels be-
fore performing idle check or adjustment, or any
engine running tests.
OBTAINING DIAGNOSTIC TROUBLE CODES
(1) Connect DRBII scan tool to the data link connec-
tor (Fig. 1). (2) Start the engine if possible, cycle the trans mis-
sion 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 display changes, assume 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. Speed Control Resume
Brake Switch
Speed Control On/Off
Speed Control Set
A/C Switch Sense
S/C Vent Solenoid S/C Vacuum Solenoid
A/C Clutch Relay
Baro Read Solenoid
Wastegate Solenoid
Auto Shutdown Relay
Radiator Fan Relay
Purge Solenoid
Malfunction Indicator Lamp (Check Engine Lamp)
STATE DISPLAY SENSORS
Connect the DRBII scan tool to the vehicle and ac-
cess the State Display screen. Then access Sensor
Display. The following is a list of the engine control
system functions accessible through the Sensor Dis-
play screen. Oxygen Sensor Signal
Coolant Temperature
Coolant Temp Sensor
Throttle Position
Minimum Throttle
Knock Sensor Signal
Battery Voltage
MAP Sensor Reading
Idle Air Control Motor Position
Adaptive Fuel Factor
Barometric Pressure
Min Airflow Idle Spd (speed)
Engine Speed
DIS Sensor Status
Fault #1 Key-On Info
Module Spark Advance
Cyl 1 Knock Retard
Cyl 2 Knock Retard
Cyl 3 Knock Retard
Cyl 4 Knock Retard
Boost Pressure Goal
Charge Temperature
Charge Temp Sensor
Speed Control Target
Fault #2 Key-on Info
Fault #3 Key-on Info
Speed Control Status
Charging System Goal
Theft Alarm Status
DIAGNOSTIC TROUBLE CODE DESCRIPTION (CON'T)
14 - 104 FUEL SYSTEMS Ä

(8) Cover or plug the injector ports with while ser-
vicing the injectors (Fig. 9).
INSTALLATION
(1) Ensure the injectors are seated into the re-
ceiver cup, with the lock ring in place. (2) Ensure the injector wiring connectors are fully
inserted into the fuel injectors. (3) Make sure the injector holes are clean and all
plugs have been removed (Fig. 9). (4) Lubricate the injector O-rings with a drop of
clean engine oil. (5) Install the injector assemblies into their holes
and install the attaching bolts. Draw the fuel rail as-
sembly evenly into the intake manifold, making sure
each injector enters its own hole. The oil separator
bracket must be on top of the fuel rail bracket (Fig.
8). (6) Once all injectors are evenly seated, tighten the
fuel rail attaching bolts to 23 N Im (200 in. lbs.)
torque. (7) Connect the fuel injector wiring harness to the
main harness. (8) Lubricate the ends of the chassis tubes with
clean 30 weight engine oil. (9) Connect fuel hose quick connect fittings to the
chassis fuel tubes. Pull on the fittings to ensure com-
plete connection. Refer to Quick Connect Fittings in the Fuel Deliv-
ery Section of this group. (10) Connect the vacuum hose to the fuel pressure
regulator. (11) Connect negative cable to battery.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) Relay remains energized
for either 7 minutes, until the test is stopped, or un-
til the ignition switch is turned to the Off position. (12) With the DRBII scan tool the ASD Fuel Sys-
tem Test to pressurize the fuel system to check for
leaks.
FUEL INJECTORS
Remove the fuel rail to service the injectors. Refer
to Fuel Injector Rail Assembly in this section.
REMOVAL
(1) Disconnect injector electrical connector from in-
jector. (Fig. 10).
(2) Position fuel rail assembly so that the fuel in-
jectors are easily accessible (Fig. 11).
(3) Remove injector lock ring off the fuel rail and
injector. Pull injector straight out of fuel rail receiver
cup (Fig. 11). (4) Check injector O-ring for damage. If O-ring is
damaged, it must be replaced. If injector is reused, a
protective cap must be installed on the injector tip to
prevent damage. (5) Repeat for remaining injectors.
Fig. 9 Fuel Injector Ports
Fig. 10 Fuel Rail and Injector Assembly
Fig. 11 Servicing Fuel Injectors
14 - 110 FUEL SYSTEMS Ä

INSTALLATION
(1) Before installing an injector, the rubber O-ring
must be lubricated with a drop of clean engine oil to aid
in installation. (2) Being careful not to damage the O-ring, install
injector top end into fuel rail receiver cup. (3) Install injector lock ring by sliding open end into
slot of the injector and onto the receiver cup ridge into
the side slots of ring (Fig. 11). (4) Repeat steps for remaining injectors.
(5) Install injector wiring harness to injectors. Place
harness into retaining clips.
FUEL PRESSURE REGULATOR
WARNING: THE 2.2L TURBO III FUEL SYSTEM IS
UNDER A CONSTANT PRESSURE OF APPROXI-
MATELY 380 KPA (55 PSI). PERFORM FUEL PRES-
SURE RELEASE PROCEDURE BEFORE SERVICING
THE FUEL PRESSURE REGULATOR.
REMOVAL
(1) Perform fuel system pressure release procedure.
(2) Disconnect negative cable from battery.
(3) Disconnect vacuum hose from fuel pressure regu-
lator (Fig. 12).
Place a shop towel under fuel pressure regula-
tor to absorb any fuel spillage. (4) Loosen fuel hose clamp and remove fuel return
hose. (5) Remove fuel pressure regulator mounting nuts.
Remove fuel pressure regulator from rail (Fig. 12).
Check O-Ring for damage. If O-Ring is damaged it
must be replaced.
INSTALLATION
(1) Lubricate O-ring with a drop of clean engine oil.
Install O-ring into the receiver cup on fuel rail. (2) Install fuel pressure regulator mounting nuts.
Tighten nuts to 7 N Im (65 in. lbs.) torque. (3) Connect fuel return hose to pressure regulator.
Tighten hose clamp to 1 N Im (10 in. lbs.) torque (Fig.
12). (4) Install vacuum hose on fuel pressure regulator.
(5) Connect negative cable to battery.
CAUTION: When using the ASD Fuel System Test,
the Auto Shutdown (ASD) Relay remains energized
for either 7 minutes, until the test is stopped, or un-
til the ignition switch is turned to the Off position. (6) With the DRBII scan tool the ASD Fuel System
Test to pressurize system and check for leaks.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
SERVICE
(1) Remove vacuum hose from MAP sensor (Fig.
13) (2) Remove MAP sensor mounting screws (Fig. 13).
(3) Remove electrical connector. Remove sensor.
(4) Reverse the above procedure for installation.
WASTEGATE AND CANISTER PURGE SOLENOID
SERVICE
(1) Remove vacuum hoses from sensors (Fig. 14).
(2) Disconnect electrical connector from solenoids
(Fig. 14). (3) Remove solenoid pack mounting nut. Remove
solenoid pack. (4) Depress tab on top of solenoid to be replaced
and slide the solenoid downward out of mounting
bracket. (5) Reverse above procedure to install.
PCM SERVICE
(1) Remove air cleaner duct from PCM.
(2) Remove battery.
(3) Remove PCM mounting screws (Fig. 15).
(4) Disconnect the 60-way wiring connector. Re-
move the PCM. (5) Reverse the above procedure for installation.
Fig. 13 Manifold Absolute Pressure Sensor
Fig. 12 Servicing Fuel Pressure Regulator
Ä FUEL SYSTEMS 14 - 111

3.0L MULTI-PORT FUEL INJECTIONÐSYSTEM OPERATION INDEX
page page
Air Conditioning (A/C) Clutch Relay (AA, AG, AJ Body)ÐPCM Output .................... 118
Air Conditioning (A/C) Clutch Relay (AC Body) ÐPCM Output ........................ 118
Air Conditioning Switch Sense (AA, AG, AJ Body)ÐPCM Input ..................... 115
Air Conditioning Switch Sense (AC Body)ÐPCM Input ................................ 115
Auto Shutdown (ASD) Relay and Fuel Pump RelayÐPCM Output .................... 119
Battery VoltageÐPCM Input ............... 115
Brake SwitchÐPCM Input ................. 115
CCD Bus .............................. 113
Data Link ConnectorÐPCM Output .......... 120
Distributor Pick-UpÐPCM Input ............. 115
Duty Cycle Evap Canister Purge Solenoid ÐPCM Output ........................ 119
Engine Coolant Temperature Sensor ÐPCM Input ......................... 115
Fuel InjectorsÐPCM Output ............... 120
Fuel Pressure Regulator .................. 124
Fuel Supply Circuit ...................... 123
General Information ...................... 113 Generator FieldÐPCM Output
.............. 118
Heated Oxygen Sensor (O
2Sensor)
ÐPCM Input ......................... 116
Idle Air Control MotorÐPCM Output ......... 119
Ignition CoilÐPCM Output ................. 121
Malfunction Indicator Lamp (Check Engine Lamp)ÐPCM Output ................... 120
Manifold Absolute Pressure (MAP) Sensor ÐPCM Input ......................... 116
Modes of Operation ...................... 121
Park/Neutral SwitchÐPCM Input ............ 117
Part Throttle Unlock SolenoidÐPCM Output . . . 121
Powertrain Control Module ................. 113
Radiator Fan RelayÐPCM Output ........... 121
Speed Control SolenoidsÐPCM Output ....... 121
Speed ControlÐPCM Input ................ 117
System Diagnosis ....................... 113
TachometerÐPCM Output ................. 121
Throttle Body ........................... 123
Throttle Position Sensor (TPS)ÐPCM Input .... 117
Transaxle Control ModuleÐPCM Output ...... 120
Vehicle Speed and Distance InputÐPCM Input . 118
Vehicle Speed SensorÐPCM Input .......... 118
GENERAL INFORMATION
The 3.0L engine uses a sequential Multi-Port Elec-
tronic Fuel Injection system (Fig. 1). The MPI system
is computer regulated and provides precise air/fuel
ratios for all driving conditions. The MPI system is operated by the powertrain con-
trol module (PCM). The PCM regulates ignition timing, air-fuel ratio,
emission control devices, cooling fan, charging sys-
tem, idle speed and speed control. Various sensors
provide the inputs necessary for the PCM to correctly
operate these systems. In addition to the sensors,
various switches also provide inputs to the PCM. All inputs to the PCM are converted into signals.
The PCM can adapt its programming to meet chang-
ing operating conditions. Fuel is injected into the intake port above the in-
take valve in precise metered amounts through elec-
trically operated injectors. The PCM fires the
injectors in a specific sequence. The PCM maintains
an air fuel ratio of 14.7 parts air to 1 part fuel by
constantly adjusting injector pulse width. Injector
pulse width is the length of time the injector is ener-
gized. The PCM adjusts injector pulse width by opening
and closing the ground path to the injector. Engine
RPM (speed) and manifold absolute pressure (air
density) are the primary inputs that determine injec-
tor pulse width.
SYSTEM DIAGNOSIS
The powertrain control module (PCM) tests many
of its own input and output circuits. If a fault is
found in a major system, the information is stored in
memory. Technicians can display fault information
through the malfunction indicator lamp (instrument
panel Check Engine lamp) or by connecting the
DRBII scan tool. For diagnostic trouble code informa-
tion, refer to the 3.0 Multi-Port Fuel InjectionÐOn-
Board Diagnostics section of this group.
CCD BUS
Various modules exchange information through a
communications port called the CCD Bus. The pow-
ertrain control module (PCM) transmits the malfunc-
tion indicator (instrument panel check engine lamp)
On/Off signal, engine RPM and vehicle load data on
the CCD Bus.
POWERTRAIN CONTROL MODULE
The powertrain control module (PCM) is a digital
computer containing a microprocessor (Fig. 2). The
PCM receives input signals from various switches
and sensors that are referred to as PCM Inputs.
Based on these inputs, the PCM adjusts various en-
gine and vehicle operations through devices referred
to as PCM Outputs. PCM Inputs:
² Air Conditioning Controls
² Battery Voltage
² Brake Switch
Ä FUEL SYSTEMS 14 - 113

tially energizes all injectors at the same time. Once
the PCM determines crankshaft position, it begins
energizing the injectors in sequence.Battery voltage is supplied to the injectors through
the ASD relay. The PCM provides the ground path
for the injectors. By switching the ground path on
and off, the PCM adjusts injector pulse width. Pulse
width is the amount of time the injector is energized.
The PCM adjusts injector pulse width based on in-
puts it receives.
IGNITION COILÐPCM OUTPUT
The auto shutdown (ASD) relay provides battery
voltage to the ignition coil. The PCM provides a
ground contact (circuit) for energizing coil. When the
PCM breaks the contact, the energy in the coil pri-
mary transfers to the secondary causing the spark.
The PCM will de-energize the ASD relay if it does
not receive an input from the distributor pick-up. Re-
fer to Auto Shutdown (ASD) Relay/Fuel Pump Re-
layÐPCM Output in this section for relay operation. The ignition coil is mounted on a bracket next to
the air cleaner (Fig. 18).
PART THROTTLE UNLOCK SOLENOIDÐPCM
OUTPUT
Three-speed automatic transaxles use a part throt-
tle unlock solenoid. The PCM controls the lock-up of
the torque convertor through the part throttle unlock
solenoid. The transaxle is locked up only in direct
drive mode. Refer to Group 21 for transaxle informa-
tion.
RADIATOR FAN RELAYÐPCM OUTPUT
The radiator fan is energized by the PCM through
the radiator fan relay. The radiator fan relay is lo-
cated on the drivers side fender well near to the
PCM. The PCM grounds the relay when engine cool-
ant reaches a predetermined temperature or the air
conditioning system turns on. On AA body vehicles, the relay is located next to
the drivers side strut tower (Fig. 13). On AC, AG and AJ body vehicles, the relay is lo-
cated in the power distribution center (Fig. 12 or Fig.
14).
SPEED CONTROL SOLENOIDSÐPCM OUTPUT
The speed control vacuum and vent solenoids are
operated by the PCM. When the PCM supplies a
ground to the vacuum and vent solenoids, the speed
control system opens the throttle blade. When the
PCM supplies a ground only to the vent solenoid, the
throttle blade holds position. When the PCM removes
the ground from both the vacuum and vent solenoids,
the throttle blade closes. The PCM balances the two
solenoids to maintain the set speed. Refer to Group
8H for speed control information.
TACHOMETERÐPCM OUTPUT
The PCM supplies engine RPM to the instrument
panel tachometer through the CCD Bus. The CCD
Bus is a communications port. Various modules use
the CCD Bus to exchange information. Refer to
Group 8E for more information.
MODES OF OPERATION
As input signals to the PCM change, the PCM ad-
justs its response to the output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than for wide open
throttle (WOT). There are several different modes of
operation that determine how the PCM responds to
the various input signals. There are two different areas of operation, OPEN
LOOP and CLOSED LOOP. During OPEN LOOP modes the PCM receives in-
put signals and responds according to preset PCM
programming. Input from the oxygen (O
2) sensor is
not monitored during OPEN LOOP modes. During CLOSED LOOP modes the PCM does mon-
itor the oxygen (O
2) sensor input. This input indi-
cates to the PCM if the injector pulse width results
in an air-fuel ratio of 14.7 parts air to 1 part fuel. By
monitoring the exhaust oxygen content through the
O
2sensor, the PCM can fine tune the injector pulse
width. Fine tuning injector pulse width allows the
PCM to achieve optimum fuel economy combined
with low emissions. The 3.0L sequential MPI system has the following
modes of operation:
² Ignition switch ONÐZero-RPM
² Engine start-up
² Engine warm-up
² Cruise (Idle)
² Acceleration
² Deceleration
² Wide Open Throttle
² Ignition switch OFF
Fig. 18 Ignition Coil
Ä FUEL SYSTEMS 14 - 121