1993 CHEVROLET PLYMOUTH ACCLAIM key battery

MALFUNCTION INDICATOR LAMP (CHECK ENGINE
LAMP)ÐPCM OUTPUT
The malfunction indicator lamp (instrument panel
Check Engine lamp) comes on each time the ignition
key is turned ON and stays on for 3 seconds as a bulb
test. The malfunction indicator lamp warns the opera-
tor that the PCM has entered a Limp-in mode. During
Limp-in Mode, the PCM attempts to keep the system
operational. The malfunction indicator lamp signals
the need for immediate service. In limp-in mode, the
PCM compensates for the failure of certain components
that send incorrect signals. The PCM substitutes for
the incorrect signals with inputs from other sensors. Signals that can trigger the malfunction indi-
cator lamp (Check Engine Lamp).
² Engine Coolant Temperature Sensor
² Manifold Absolute Pressure Sensor
² Throttle Position Sensor
² Battery Voltage Input
² An Emission Related System (California vehicles)
² Charging system
The malfunction indicator lamp displays diagnostic
trouble codes. Cycle the ignition switch on, off, on, off,
on, within five seconds to display any diagnostic
trouble codes stored in the PCM. Refer to the 3.0L
Multi-Port Fuel InjectionÐOn-Board Diagnostics sec-
tion of this Group for Diagnostic trouble code Descrip-
tions.
DATA LINK CONNECTORÐPCM OUTPUT
The data link connector provides the technician with
the means to connect the DRBII scan tool to diagnosis
the vehicle.
TRANSAXLE CONTROL MODULEÐPCM OUTPUT
The PCM supplies the following information to the
electronic automatic transaxle control module through
the CCD Bus:
² battery temperature ²
brake switch input
² engine coolant temperature
² manifold absolute pressure (MAP)
² speed control information
FUEL INJECTORSÐPCM OUTPUT
The fuel injectors are electrical solenoids (Fig. 16).
The injector contains a pintle that closes off an ori-
fice at the nozzle end. When electric current is sup-
plied to the injector, the armature and pintle move a
short distance against a spring, allowing fuel to flow
out the orifice. Because the fuel is under high pres-
sure, a fine spray is developed in the shape of a hol-
low cone. The spraying action atomizes the fuel,
adding it to the air entering the combustion cham-
ber.
The injectors are positioned in the intake manifold
with the nozzle ends directly above the intake valve
port (Fig. 16).
The fuel injectors are operated by the PCM. They
are energized in a sequential order during all engine
operating conditions except start up. The PCM ini-
Fig. 16 Fuel InjectorÐ3.0L Engine
Fig. 17 Fuel Injector Location
Fig. 15 EVAP Purge Solenoid
14 - 120 FUEL SYSTEMS Ä

The engine start-up (crank), engine warm-up, and
wide open throttle modes are OPEN LOOP modes. The
acceleration, deceleration, and cruise modes, with the
engine at operating temperature are CLOSED
LOOP modes (under most operating conditions).
IGNITION SWITCH ON (ZERO RPM) MODE
When the multi-port fuel injection system is acti-
vated by the ignition switch, the following actions
occur:
² The PCM determines atmospheric air pressure from
the MAP sensor input to determine basic fuel strategy.
² The PCM monitors the coolant temperature sensor
and throttle position sensor input. The PCM modifies
fuel strategy based on these inputs. When the key is in the ON position and the engine is
not running (zero rpm), the auto shutdown (ASD) relay
and fuel pump relay are not energized. Therefore
battery voltage is not supplied to the fuel pump,
ignition coil, fuel injectors or oxygen sensor heating
element.
ENGINE START-UP MODE
This is an OPEN LOOP mode. The following actions
occur when the starter motor is engaged. If the PCM receives a distributor signal, it energizes
the auto shutdown (ASD) relay and fuel pump relay.
These relays supply battery voltage to the fuel pump,
fuel injectors, ignition coil, and oxygen sensor heating
element. If the PCM does not receive a distributor
input, the ASD relay and fuel pump relay will be
de-energized after approximately one second. The PCM energizes all six injectors until it deter-
mines crankshaft position from the distributor pick-up
signals. The PCM determines crankshaft position
within 2 engine revolutions. After determining crankshaft position, the PCM be-
gins energizing the injectors in sequence. The PCM
adjusts injector pulse width and controls injector syn-
chronization by turning the individual ground paths to
the injectors On and Off. When the engine idles within 664 RPM of its target
RPM, the PCM compares current MAP sensor value
with the atmospheric pressure value received during
the Ignition Switch On (zero RPM) mode. If the PCM
does not detect a minimum difference between the two
values, it sets a MAP fault into memory. Once the ASD and fuel pump relays have been
energized, the PCM:
² determines injector pulse width based on coolant
temperature, manifold absolute pressure (MAP) and
the number of engine revolutions since cranking was
initiated. ²
monitors the coolant temperature sensor, distribu-
tor pick-up, MAP sensor, and throttle position sensor
to determine correct ignition timing.
ENGINE WARM-UP MODE
This is a OPEN LOOP mode. The following inputs
are received by the PCM:
² engine coolant temperature
² crankshaft position (distributor pick-up)
² manifold absolute pressure (MAP)
² engine speed (distributor pick-up)
² throttle position
² A/C switch
² battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off. The PCM adjusts engine idle speed by regulating
the idle air control motor and ignition timing.
CRUISE OR IDLE MODE
When the engine is at operating temperature this
is a CLOSED LOOP mode. During cruising speed the
following inputs are received by the PCM:
² engine coolant temperature
² crankshaft position (distributor pick-up)
² manifold absolute pressure
² engine speed (distributor pick-up)
² throttle position
² exhaust gas oxygen content
² A/C control positions
² battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off. The PCM adjusts engine idle speed and ignition
timing. The PCM controls the air/fuel ratio according
to the oxygen content in the exhaust gas.
ACCELERATION MODE This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in throttle position or MAP
pressure as a demand for increased engine output
and vehicle acceleration. The PCM increases injector
pulse width in response to increased fuel demand.
DECELERATION MODE This is a CLOSED LOOP mode. During decelera-
tion the following inputs are received by the PCM:
² engine coolant temperature
² crankshaft position (distributor pick-up)
² manifold absolute pressure
² engine speed (distributor pick-up)
² throttle position
² exhaust gas oxygen content
² A/C control positions
² battery voltage
14 - 122 FUEL SYSTEMS Ä

SYSTEM TESTS
WARNING: APPLY PARKING BRAKE AND/OR BLOCK
WHEELS BEFORE PERFORMING ANY TEST ON AN
OPERATING ENGINE.
OBTAINING DIAGNOSTIC TROUBLE CODES
(1) Connect DRBII scan tool to the data link connec-
tor located in the engine compartment near the pow-
ertrain control module (PCM). (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 3 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. 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
S/C Vacuum Solenoid
A/C Clutch Relay
EGR Solenoid
Auto Shutdown Relay
Radiator Fan Relay
Purge Solenoid
Torque Converter Clutch 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. Battery Temperature
Oxygen Sensor Signal
Engine Coolant Temperature
Engine Coolant Temp Sensor
Throttle Position
Minimum Throttle
Battery Voltage
MAP Sensor Reading
Idle Air Control Motor Position
Adaptive Fuel Factor
Barometric Pressure
Min Airflow Idle Speed
Engine Speed
Fault #1 Key-On Info
Module Spark Advance
Speed Control Target
Fault #2 Key-on Info
Fault #3 Key-on Info
Speed Control Status
Speed Control Switch Voltage
Charging System Goal
Theft Alarm Status
Map Sensor Voltage
Vehicle Speed
Oxygen Sensor State
MAP Gauge Reading
Throttle Opening (percentage)
Total Spark Advance
CIRCUIT ACTUATION TEST MODE
The circuit actuation test mode checks for proper
operation of output circuits or devices which the pow-
ertrain control module (PCM) cannot internally rec-
ognize. The PCM can attempt to activate these
outputs and allow an observer to verify proper oper-
ation. Most of the tests provide an audible or visual
indication of device operation (click of relay contacts,
spray fuel, etc.). Except for intermittent conditions, if
a device functions properly during testing, assume
the device, its associated wiring, and driver circuit
working correctly.
OBTAINING CIRCUIT ACTUATION TEST
Connect the DRBII scan tool to the vehicle and ac-
cess the Actuators screen. The following is a list of
the engine control system functions accessible
through Actuators screens. Stop All Tests
Ignition Coil #1
Fuel Injector #1
Fuel Injector #2
Fuel Injector #3
14 - 134 FUEL SYSTEMS Ä

(18) Remove fuel rail mounting bolts. Lift fuel rail
assembly off of intake manifold.
INSTALLATION
(1) Be sure injectors are seated into the receiver
cup with lock ring in place. (2) Make sure the injector holes are clean and all
plugs have been removed. (3) To ease installation, lubricate injector O-ring
with a drop of clean engine oil. (4) Put the tip of each injector into their ports.
Push the assembly into place until the injectors are
seated in the ports. (5) Install fuel rail attaching bolts. Tighten bolts
to 13 N Im (115 in. lbs.) torque.
(6) Install fuel supply and return tube holddown
bolt and the vacuum crossover tube holddown bolt.
Tighten bolts to 10 N Im (95 in. lbs.) torque.
(7) Connect fuel injector wiring harness to engine
wiring harness. (8) Connect vacuum harness to fuel rail assembly.
(9) Remove covering from lower intake manifold
and clean surface. (10) Place intake manifold gaskets with beaded
sealer up on lower manifold. Put air intake in place.
Install ignition coil. Install attaching fasteners and
tighten to 13 N Im (115 in. lbs.) torque.
(11) Connect fuel lines to fuel rail. Tighten hose
clamps to 1 N Im (10 in. lbs.) torque.
(12) Connect vacuum harness to air intake plenum
and fuel pressure regulator. (13) Connect coolant temperature sensor electrical
connector to sensor. (14) Connect EGR tube flange to intake plenum.
Tighten mounting nuts to 22 N Im (200 in. lbs.)
torque. (15) Connect PCV and brake booster supply hose
to intake plenum. (16) Connect idle air control motor and throttle po-
sition sensor (TPS) electrical connectors. (17) Connect vacuum vapor harness to throttle
body. (18) Install throttle cable.
(19) Install air inlet hose assembly.
(20) 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. (21) With the ignition key in ON position, access
the DRBII scan tool ASD Fuel System Test to pres-
surize the fuel system. Check for leaks.
FUEL PRESSURE REGULATOR SERVICE
REMOVAL
WARNING: THE 3.0L MPI FUEL SYSTEM IS UNDER
A CONSTANT PRESSURE OF APPROXIMATELY 330
KPA (48 PSI). PERFORM FUEL PRESSURE RE-
LEASE PROCEDURE BEFORE SERVICING THE
FUEL PRESSURE REGULATOR.
(1) Perform the Fuel Pressure Release Procedure.
(2) Disconnect negative cable from battery.
Fig. 10 Removing Air Intake Plenum
Fig. 11 Vacuum Connections at the Fuel Rail
Fig. 12 Fuel Injector Wiring Harness
Ä FUEL SYSTEMS 14 - 141

(3) Loosen fuel return hose clamp and remove fuel
return hose from nipple. (4) Remove vacuum hose from fuel pressure regu-
lator. (Fig. 13). (5) Remove screw holding fuel return tube to the
intake manifold. (6) Remove fuel pressure regulator screws. Remove
fuel pressure regulator from engine.
INSTALLATION
(1) Lubricate O-ring on fuel pressure regulator
with clean 30 weight engine oil. (2) Install fuel pressure regulator into fuel rail.
Tighten screws to 10 N Im (90 in. lbs.) torque.
(3) Install screw holding fuel return tube clamp in
place. Tighten screw to 10 N Im (95 in. lbs.) torque.
(4) Connect vacuum hose to fuel pressure regula-
tor. (5) Connect fuel return hose to fuel return tube.
Tighten hose clamp to 1 N Im (10 in. lbs.) torque.
(6) Connect negative battery cable.
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.
(7) With the ignition key in ON position, access
the DRBII scan tool's ASD Fuel System Test to pres-
surize the fuel system. Check for leaks.
FUEL INJECTORS
WARNING: THE 3.0L MPI FUEL SYSTEM IS UNDER
A CONSTANT PRESSURE OF APPROXIMATELY 330
KPA (48 PSI). PERFORM FUEL PRESSURE RE-
LEASE PROCEDURE BEFORE SERVICING THE
FUEL INJECTORS.
REMOVAL
(1) Perform the Fuel Pressure Release Procedure.
(2) Disconnect negative cable from battery.
The fuel rail must be removed first to service the
injectors. Refer to Fuel Injector Rail Assembly Re-
moval in this section. (3) Label each injector connector with its cylinder
number. Disconnect electrical connector from injec-
tor. (4) Position fuel rail assembly so that the fuel in-
jectors are easily accessible. (5) Remove injector clip from fuel rail and injector
(Fig. 14).
(6) Pull injector straight out of fuel rail receiver
cup (Fig. 15).
Fig. 13 Fuel Pressure Regulator
Fig. 14 Fuel Injector and Rail
Fig. 15 Servicing Fuel Injector
14 - 142 FUEL SYSTEMS Ä

(7) Check injector O-ring for damage. If O-ring is
damaged, it must be replaced. If injector is to be re-
used, a protective cap must be installed on the injec-
tor tip to prevent damage. (8) Repeat procedure for remaining injectors.
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 O-ring, install in-
jector nozzle end into fuel rail receiver cap (Fig. 15). (3) Install injector clip by sliding open end into top
slot of the injector. The edge of the receiver cup will
slide into the side slots of clip (Fig. 14). (4) Repeat steps for remaining injectors.
(5) Install fuel rail assembly. Refer to Fuel Rail
Assembly Installation in this section. (6) Connect electrical connectors to injectors in cor-
rect order. (7) Connect negative battery cable.
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.
(8) With the ignition key in ON position, access
the DRBII scan tool ASD Fuel System Test to pres-
surize the fuel system. Check for leaks.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
(1) Remove vacuum hose and mounting screws
from manifold absolute pressure (MAP) sensor (Fig.
16).
(2) Disconnect electrical connector from sensor. Re-
move sensor. (3) Reverse the above procedure for installation.
CANISTER PURGE SOLENOID SERVICE
(1) Remove vacuum hose and electrical connector
from solenoid (Fig. 17).
(2) Slide solenoid and silencer assembly off of
bracket. (3) Reverse above procedure to install.
PCM
(1) Remove air cleaner duct from PCM.
(2) Disconnect negative cable from battery. Discon-
nect positive cable from battery. (3) Remove battery holddown. Remove battery.
(4) Remove PCM mounting screws (Fig. 18, Fig. 19
or Fig. 20). (5) Remove the electrical connector from PCM. Re-
move PCM. (6) Reverse the above procedure for installation.
Fig. 16 Manifold Absolute Pressure Sensor
Fig. 17 Canister Purge Solenoid
Fig. 18 PCMÐAA Body
Ä FUEL SYSTEMS 14 - 143

within a range of 12.9 to 15.0 volts. Refer to Group
8A for charging system information.
AUTO SHUTDOWN (ASD) RELAY AND FUEL PUMP
RELAYÐPCM OUTPUT
The PCM operates the auto shutdown (ASD) relay
and fuel pump relay through one ground path. The
PCM operates the relays by switching the ground
path on and off. Both relays turn on and off at the
same time. The ASD relay connects battery voltage to the fuel
injector and ignition coil. The fuel pump relay con-
nects battery voltage to the fuel pump and oxygen
sensor heating element. The PCM turns the ground path off when the igni-
tion switch is in the Off position. Both relays are off.
When the ignition switch is in the On or Crank po-
sition, the PCM monitors the crankshaft position
sensor and camshaft position sensor signals to deter-
mine engine speed and ignition timing (coil dwell). If
the PCM does not receive the crankshaft position
sensor and camshaft position sensor signals when the
ignition switch is in the Run position, it de-energizes
both relays. When the relays are de-energized, bat-
tery voltage is not supplied to the fuel injector, igni-
tion coil, fuel pump and oxygen sensor heating
element. The ASD relay and fuel pump relay are located in
the power distribution center (Fig. 14).
IDLE AIR CONTROL MOTORÐPCM OUTPUT
The idle air control motor is mounted on the throt-
tle body. The PCM operates the idle air control motor
(Fig. 13). The PCM adjusts engine idle speed through
the idle air control motor to compensate for engine
load or ambient conditions. The throttle body has an air bypass passage that
provides air for the engine at idle (the throttle blade is closed). The idle air control motor pintle protrudes
into the air bypass passage and regulates air flow
through it. The PCM adjusts engine idle speed by moving the
idle air control motor pintle in and out of the bypass
passage. The adjustments are based on inputs the
PCM receives. The inputs are from the throttle posi-
tion sensor, crankshaft position sensor, coolant tem-
perature sensor, and various switch operations
(brake, park/neutral, air conditioning). Deceleration
die out is also prevented by increasing airflow when
the throttle is closed quickly after a driving (speed)
condition.
CANISTER PURGE SOLENOIDÐPCM OUTPUT
Vacuum for the Evaporative Canister is controlled
by the Canister Purge Solenoid (Fig. 15). The sole-
noid is controlled by the PCM.
The PCM operates the solenoid by switching the
ground circuit on and off based on engine operating
conditions. When energized, the solenoid prevents
vacuum from reaching the evaporative canister.
When not energized the solenoid allows vacuum to
flow to the canister. The PCM removes the ground to the solenoid when
the engine reaches a specified temperature and the
time delay interval has occurred. When the solenoid
is de-energized, vacuum flows to the canister purge
valve. Vapors are purged from the canister and flow
to the throttle body. The purge solenoid will also be energized during
certain idle conditions, in order to update the fuel de-
livery calibration.
MALFUNCTION INDICATOR LAMP (CHECK ENGINE
LAMP)ÐPCM OUTPUT
The malfunction indicator lamp (instrument panel
Check Engine Lamp) comes on each time the ignition
key is turned ON and stays on for 3 seconds as a
bulb test. The malfunction indicator lamp warns the
Fig. 14 Relay Identification
Fig. 15 Canister Purge Solenoid
Ä FUEL SYSTEMS 14 - 151

IGNITION SWITCH ON (ZERO RPM) MODE When the multi-port fuel injection system is acti-
vated by the ignition switch, the following actions oc-
cur:
² The PCM determines atmospheric air pressure
from the MAP sensor input to determine basic fuel
strategy.
² The PCM monitors the coolant temperature sensor
and throttle position sensor input. The PCM modifies
fuel strategy based on this input. When the key is in the ON position and the engine
is not running (zero rpm), the auto shutdown (ASD)
relay and fuel pump relay are not energized. There-
fore battery voltage is not supplied to the fuel pump,
ignition coil, fuel injectors or oxygen sensor heating
element.
ENGINE START-UP MODE
This is an OPEN LOOP mode. The following ac-
tions occur when the starter motor is engaged. If the PCM receives the camshaft position sensor
and crankshaft position sensor signals, it energizes
the auto shutdown (ASD) relay and fuel pump relay.
These relays supply battery voltage to the fuel pump,
fuel injectors, ignition coil, and oxygen sensor heat-
ing element. If the PCM does not receive the cam-
shaft position sensor and crankshaft position sensor
signals within approximately one second, it de-ener-
gizes the ASD relay and fuel pump relay. The PCM energizes all six injectors until it deter-
mines crankshaft position from the camshaft position
sensor and crankshaft position sensor signals. The
PCM determines crankshaft position within 1 engine
revolution. After determining crankshaft position, the PCM
begins energizing the injectors in sequence. The PCM
adjusts injector pulse width and controls injector syn-
chronization by turning the individual ground paths
to the injectors On and Off. When the engine idles within 664 RPM of its tar-
get RPM, the PCM compares current MAP sensor
value with the atmospheric pressure value received
during the Ignition Switch On (Zero RPM) mode. If
the PCM does not detect a minimum difference be-
tween the two values, it sets a MAP fault into mem-
ory. Once the ASD and fuel pump relays have been en-
ergized, the PCM:
² Determines injector pulse width based on battery
voltage, coolant temperature, engine rpm and the
number of engine revolutions since cranking was ini-
tiated.
ENGINE WARM-UP MODE This is a OPEN LOOP mode. The following inputs
are received by the PCM:
² engine coolant temperature ²
manifold absolute pressure (MAP)
² engine speed (crankshaft position sensor)
² throttle position
² A/C switch
² battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off. The PCM adjusts ignition timing and engine idle
speed. Engine idle speed is adjusted through the idle
air control motor.
CRUISE OR IDLE MODE
When the engine is at operating temperature this
is a CLOSED LOOP mode. During cruising speed the
following inputs are received by the PCM:
² engine coolant temperature
² manifold absolute pressure
² engine speed (crankshaft position sensor)
² throttle position
² exhaust gas oxygen content
² A/C control positions
² battery voltage
The PCM adjusts injector pulse width and controls
injector synchronization by turning the individual
ground paths to the injectors On and Off. The PCM adjusts engine idle speed and ignition
timing. The PCM adjusts the air/fuel ratio according
to the oxygen content in the exhaust gas.
ACCELERATION MODE This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in throttle position or MAP
pressure as a demand for increased engine output
and vehicle acceleration. The PCM increases injector
pulse width in response to increased fuel demand.
DECELERATION MODE This is a CLOSED LOOP mode. During decelera-
tion the following inputs are received by the PCM:
² engine coolant temperature
² manifold absolute pressure
² engine speed
² throttle position
² exhaust gas oxygen content
² A/C control positions
² battery voltage
The PCM may receive a closed throttle input from
the throttle position sensor (TPS) when it senses an
abrupt decrease in manifold pressure. This indicates
a hard deceleration. The PCM will reduce injector
pulse width. This helps maintain better control of the
air-fuel mixture (as sensed through the O
2sensor).
During a closed throttle deceleration condition, the
PCM grounds the exhaust gas recirculation (EGR)
solenoid. When the solenoid is grounded, EGR func-
tion stops.
14 - 154 FUEL SYSTEMS Ä