key CHEVROLET DYNASTY 1993 Manual Online

REMOVAL
(1) Perform the Fuel System Pressure Release pro-
cedure. (2) ) Remove the fuel filter retaining screw (Fig.
13). Remove fuel filter from mounting plate.
(3) Wrap a shop towel around hoses to absorb fuel.
Remove quick-connect fittings at filter and fuel supply
tube. Refer to Quick-Connect Fittings in this section.
INSTALLATION
WARNING: FUEL FILTERS DESIGNED FOR GASO-
LINE ONLY VEHICLES CANNOT BE USED ON
FLEXIBLE FUEL AA-BODY VEHICLES. WHEN SER-
VICING THE FUEL SYSTEM OF A FLEXIBLE FUEL
VEHICLE, ONLY USE ORIGINAL EQUIPMENT OR
EQUIVALENT REPLACEMENT COMPONENTS.
(1) Connect quick-connect fuel fittings to the filter
and fuel supply line. Refer to Quick-Connect Fittings
in this section. (2) Position filter assembly on mounting plate and
tighten mounting screw to 8 N Im (75 in. lbs.) torque.
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.
(3) Place the ignition key in the ON position. Us-
ing the DRBII scan tool, access ASD Fuel System
Test. The ASD Fuel System Test will activate the
fuel pump and pressurize the system. Inspect for
leaks.
FUEL HOSES, CLAMPS, AND QUICK CONNECT
FITTINGS
HOSES AND CLAMPS
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.
WARNING: FUEL SYSTEM HOSES AND TUBES DE-
SIGNED FOR GASOLINE ONLY VEHICLES CANNOT
BE USED ON FLEXIBLE FUEL VEHICLES. WHEN
SERVICING THE FUEL SYSTEM OF A FLEXIBLE
FUEL VEHICLE, ONLY USE ORIGINAL EQUIPMENT
OR EQUIVALENT REPLACEMENT COMPONENTS.
Inspect all hose connections (clamps and quick con-
nect fittings) for completeness and make sure they
are not leaking. Hoses that are cracked, scuffed,
swelled, rub against other vehicle components or
show any sign of wear, should be replaced.
When installing hoses, route them away from compo-
nents they could rub against. Avoid contact with clamps
or other components that cause abrasions or scuffing.
Ensure rubber hoses are properly routed and avoid heat
sources. The clamps have rolled edge to prevent the clamp
from cutting into the hose. Only use clamps that are
original equipment or equivalent. Other types of clamps
may cut into the hoses and cause high pressure fuel
leaks. Tighten hose clamps to 1 N Im (10 in. lbs.) torque.
QUICK CONNECT FITTINGS
Most fuel lines have quick connect fittings. The fit-
tings speed up the installation and removal of fuel
lines (Fig. 14). Quick connect fittings consist of a metal casing, a
black plastic release ring, a metal locking retainer,
and internal O-rings.
METAL QUICK CONNECT FITTINGS
The fuel filter and fuel rail use steel quick-connect
fittings. The fitting contains non-serviceable sealed
O-rings. The fittings contain a plastic disconnect tool.
The quick-connect fitting consists of the O-rings, cas-
ing, disconnect tool and a retainer (Fig. 14). When the
Fig. 13 Fuel Filter
Fig. 14 Metal Quick-Connect Fittings
14 - 10 FUEL SYSTEMS Ä

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 is also energized during certain
idle conditions to update the fuel delivery calibration.
MALFUNCTION INDICATOR LAMP (CHECK
ENGINE)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.
² Coolant Temperature Sensor
² Manifold Absolute Pressure Sensor
² Throttle Position Sensor
² Battery Voltage Input
² An Emissions Related System
² Charging system
The malfunction indicator lamp can also be used to
display diagnostic trouble codes. Cycle the ignition
switch on, off, on, off, on, within five seconds and any
diagnostic trouble codes stored in the PCM will be
displayed. Refer to the 2.2L/2.5L Single Point Fuel
InjectionÐOn-Board Diagnostics section in this group.
DATA LINK CONNECTORÐPCM OUTPUT
The data link connector provides the technician with
the means to connect the DRBII scan tool to diagnosis
the vehicle.
ELECTRIC ELECTRONIC GAS
RECIRCULATIONÐPCM OUTPUT
The electronic exhaust gas recirculation transducer
(EET) is a back pressure transducer/electric vacuum
solenoid assembly (Fig. 13). The EET assembly mounts
above the EGR valve (Fig. 14).
The solenoid turns the vacuum supply to the trans-
ducer on and off. The electric vacuum solenoid portion
of the EET energizes when the PCM provides a ground
path. When the solenoid energizes, vacuum is pre-
vented from flowing to the transducer. When the sole-
noid de-energizes, vacuum flows to the transducer. The
solenoid energizes during engine warm-up, closed
throttle (idle or cruise), wide open throttle, and rapid
acceleration/deceleration. If the solenoid wire con-
nector is disconnected, the EGR valve will oper-
ate at all times.
Fig. 12 EVAP Canister Purge Solenoid
Fig. 13 Electronic EGR Recirculation Transducer
Fig. 14 EGR Valve and Electric EGR Transducer
14 - 30 FUEL SYSTEMS Ä

TACHOMETERÐPCM OUTPUT
The PCM supplies engine RPM to the instrument
panel tachometer. Refer to Group 8 for tachometer
information.
MODES OF OPERATION
As input signals to the PCM change, the PCM
adjusts its response to the output devices. For example,
the PCM must calculate a different injector pulse
width and ignition timing for idle than it does 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 input
signals and responds according to preset PCM pro-
gramming. Input from the oxygen (O
2) sensor is not
monitored during OPEN LOOP modes. During CLOSED LOOP modes, the PCM does moni-
tor the oxygen (O
2) sensor input. This input tells the
PCM if the calculated injector pulse width results in an
air-fuel ratio of 14.7 to 1. By monitoring the exhaust
oxygen content, the can PCM fine tune injector pulse
width for optimum fuel economy and low emissions. The single point fuel injection system has the follow-
ing modes of operation:
² Ignition switch ON - Zero RPM
² Engine start-up
² Engine warm-up
² Cruise (Idle)
² Acceleration
² Deceleration
² Wide Open Throttle
² Ignition switch OFF
The engine start-up (cranking), 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 single point 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 calculate basic fuel strategy.
² The PCM monitors the coolant temperature sensor
and throttle position sensor inputs. The PCM modifies
fuel strategy based on these inputs. When the key is in the ON position and the engine is
not running, the (ASD) and fuel pump relays are not
energized. Therefore, battery voltage is not supplied to
the fuel pump, ignition coil, fuel injector 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 to
supply battery voltage to the fuel injector, ignition coil
and oxygen sensor heating element. If the PCM does
not receive a distributor input, it de-energizes the ASD
and fuel pump relays after approximately one second. When the engine idles within 664 RPM of the target
RPM, the PCM compares the current MAP value with
the atmospheric pressure value it received during the
Ignition Switch On (Zero RPM) Mode. If a minimum
difference between the two is not detected, a MAP
sensor fault is set into memory. Once the ASD relay and fuel pump relay have ener-
gized, the PCM:
² Supplies a ground path to the injector. The injector
is pulsed four times per engine revolution instead of
the normal two pulses per revolution.
² Determines injector pulse width based on coolant
temperature, MAP sensor input, throttle position, 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 coolant temperature
² manifold absolute pressure (MAP)
² engine speed (distributor pick-up)
² throttle position
² A/C switch
² battery voltage
The PCM provides a ground path for the injector to
precisely control injector pulse width (by switching the
ground on and off) and fires the injector twice per
engine revolution. The PCM regulates ignition timing.
It also adjusts engine idle speed 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 and at
idle the following inputs are received by the PCM:
² 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
14 - 32 FUEL SYSTEMS Ä

2.2L/2.5L SINGLE POINT FUEL INJECTIONÐON-BOARD DIAGNOSTICS INDEX
page page
60-Way PCM Wiring Connector .............. 46
Circuit Actuation Test Mode ................ 45
Diagnostic Trouble Code Description .......... 42
General Information ....................... 41
High and Low Limits ...................... 42
Ignition Timing Procedure .................. 46 Monitored Circuits
........................ 41
Non-Monitored Circuits .................... 42
State Display Test Mode ................... 45
Systems Test ........................... 45
Throttle Body Minimum Air Flow Check Procedure.46
GENERAL INFORMATION
The powertrain control module (PCM) has been
programmed to monitor many different circuits of the
fuel injection system. If a problem is sensed with a
monitored circuit often enough to indicate an actual
problem, the PCM stores a fault. If the problem is re-
paired or ceases to exist, the PCM cancels the Diag-
nostic Trouble Code after 50 to 100 vehicle key on/off
cycles. Certain criteria must be met for a diagnostic trou-
ble code to be entered into powertrain control module
(PCM) memory. The criteria may be a specific range
of engine RPM, engine temperature, and/or input
voltage to the PCM. It is possible that a diagnostic trouble code for a
monitored circuit may not be entered into memory
even though a malfunction has occurred. This may
happen because one of the diagnostic trouble code
criteria for the circuit has not been met. For exam-
ple , assume that one of the diagnostic trouble code
criteria for a certain sensor circuit is that the engine
must be operating between 750 and 2000 RPM to be
monitored for a diagnostic trouble code. If the sensor
output circuit shorts to ground when engine RPM is
above 2400 RPM (resulting i n a 0 volt input to the
PCM) a diagnostic trouble code will not be entered
into memory. This is because the condition does not
occur within the specified RPM range. There are several operating conditions for which
the PCM does not monitor and set diagnostic trouble
codes. Refer to Monitored Circuits and Non-Moni-
tored Circuits in this section. Stored diagnostic trouble codes can be displayed by
cycling the ignition key On - Off - On - Off - On.
Also, the technician can display fault information us-
ing the DRB II scan tool. The DRBII scan tool con-
nects to the data link connector in the vehicle (Fig.
1,2or3).
MONITORED CIRCUITS
The powertrain control module (PCM) can detect
certain fault conditions in the fuel injection system. Open or Shorted Circuit - The PCM can deter-
mine if the sensor output (input to PCM) is within
proper range, and if the circuit is open or shorted. Output Device Current Flow
- The PCM senses
whether the output devices are hooked up. If there is
a problem with the circuit, the PCM senses whether
the circuit is open, shorted to ground, or shorted
high. Oxygen Sensor - The PCM can determine if the
oxygen sensor is switching between rich and lean
Fig. 1 Data Link Connector LocationÐAA and AP Vehicles
Fig. 2 Data Link Connector LocationÐAC Vehicles
Ä FUEL SYSTEMS 14 - 41

SYSTEMS TEST
WARNING: APPLY PARKING BRAKE AND/OR
BLOCK WHEELS BEFORE PERFORMING A TEST
WITH THE ENGINE OPERATING.
OBTAINING DIAGNOSTIC TROUBLE CODES
(1) Connect DRBII scan tool to the data link con-
nector located in the engine compartment near the
powertrain 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).
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 po-
sition versus an open circuit, a short circuit, or a de-
fective 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 ei-
ther State Display Inputs and Outputs or State Dis-
play Sensors.
STATE DISPLAY INPUTS AND OUTPUTS
Connect the DRBII scan tool to the vehicle and ac-
cess 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 (automatic transaxle only)
Speed Control Resume
Brake Switch
Speed Control On/Off
Speed Control Set
A/C Switch Sense
S/C (Speed Control) Vent Solenoid
S/C (Speed Control) Vacuum Solenoid
Torque Converter Clutch Solenoid (3 speed auto-
matic transaxle)
A/C Clutch Relay
EGR Solenoid
Auto Shutdown Relay
Radiator Fan Relay
Purge Solenoid
Malfunction Indicator (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
Battery Voltage
MAP Sensor Reading
Idle Air Control Motor Position
Added Adaptive Fuel
Adaptive Fuel Factor
Barometric Pressure
Min Airflow Idl Spd
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
Charging System Goal
Theft Alarm Status
Speed Control Switch Voltage
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.). With the exception of an intermit-
tent condition, if a device functions properly during
its test, it can be assumed that the device, its associ-
ated wiring, and its driver circuit are in working or-
der.
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
Idle Air Control Motor Open/Close
Ä FUEL SYSTEMS 14 - 45

(5) Remove throttle cable. If equipped, remove the
speed control and transaxle kickdown cables. (6) Remove return spring.
(7) Loosen fuel tube clamp on valve cover (Fig. 4).
(8) Wipe quick connect fittings to remove any dirt.
Remove fuel intake and return tubes. Refer to Fuel
Hoses, Clamps and Quick Connect Fittings in the
Fuel Delivery Section of this Group. Place a shop
towel under the connections to absorb any fuel spilled. (9) Remove throttle body mounting screws and lift
throttle body from vehicle. Remove throttle body gas-
ket from intake manifold.
INSTALLATION
(1) Using a new gasket, install throttle body and
tighten mounting screws to 20 N Im (175 in. lbs.)
torque. (2) Lubricate the ends of the fuel supply and return
tubes with clean 30 weight oil. Connect fuel lines to
quick connect fittings. Refer to Fuel Hoses, Clamps
and Quick Connect Fittings in the Fuel Delivery
Section of this Group . After the fuel tubes are
connected to the fittings, pull on the tubes to ensure
that they are fully inserted and locked into position. (3) Tighten the fuel tube clamp on the valve cover.
(4) Install return spring.
(5) Install throttle cable. If equipped, install kick-
down and speed control cables. (6) Install wiring connectors and vacuum hoses.
(7) Install air cleaner.
(8) Reconnect 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 until the
ignition switch is turned to the Off position. (9) With the ignition key in ON position, access the
DRBII scan tool ASD Fuel System Test to pressurize
the fuel system. Check for leaks.
FUEL FITTING
REMOVAL
(1) Remove air cleaner assembly.
(2) Perform Fuel System Pressure Release proce-
dure. (3) Disconnect negative battery cable.
(4) Loosen fuel tube clamp on valve cover.
(5) Wipe any dirt from around quick connect fittings.
(Fig. 5) Place a shop towel under the connections to
catch any spilled fuel. Remove fuel tubes from quick
connect fittings. Refer to Fuel Hoses, Clamps and
Quick Connect Fittings in the Fuel Delivery Sec-
tion of this Group .
(6) Remove each fitting from throttle body and note
inlet diameter. Remove copper washers.
INSTALLATION
(1) Replace copper washers with new washers.
(2) Install fuel fittings in proper ports and tighten to
20 N Im (175 in. lbs.) torque.
(3) Lubricate ends of the fuel tubes with 30 weight
oil. Insert the tubes into the quick connect fittings.
Refer to Fuel Hoses, Clamps and Quick Connect
Fittings in the Fuel Delivery Section of this
Group . After the fuel tubes are connected to the
fittings, pull on the tubes to ensure that they are fully
inserted and locked into position. (4) Tighten fuel tube clamp on valve cover.
(5) Reconnect negative battery cable.
Fig. 5 Servicing Fuel Fitting
Fig. 4 Fuel Line Clamp
14 - 50 FUEL SYSTEMS Ä

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 ignition key in ON position, access
the DRBII scan tool ASD Fuel System Test to pres-
surize the fuel system. Check for leaks. (7) Reinstall air cleaner assembly.
FUEL PRESSURE REGULATOR
The fuel pressure regulator is mounted on top of
the throttle body (Fig. 6).
REMOVAL
(1) Remove air cleaner assembly.
(2) Perform Fuel System Pressure Release proce-
dure. (3) Disconnect battery negative cable.
(4) Remove pressure regulator mounting screws
(Fig. 6).
WARNING: PLACE A SHOP TOWEL AROUND FUEL
INLET CHAMBER TO CONTAIN ANY FUEL REMAIN-
ING IN THE SYSTEM.
(5) Pull pressure regulator from the throttle body.
(6) Carefully remove O-ring from pressure regula-
tor and remove gasket.
INSTALLATION
(1) Place new gasket on pressure regulator. Care-
fully install new O-ring. (2) Position pressure regulator on throttle body.
Press regulator into place and install mounting
screws. Tighten screws to 5 N Im (40 in. lbs.) torque.
(3) 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. (4) 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. (5) Reinstall air cleaner assembly.
FUEL INJECTOR
The fuel injector is installed in the top of the throt-
tle body. The injector is covered by a cap.
REMOVAL
(1) Remove air cleaner assembly.
(2) Perform Fuel System Pressure Release proce-
dure. (3) Disconnect negative cable from battery.
(4) Remove injector cap holddown screw (Torx-
head). (5) With two small screwdrivers, lift the top off the
injector using the slots provided (Fig. 7).
(6) Using a small screwdriver placed in the hole in
the front of the electrical connector, gently pry the
injector from the pod (Fig. 8).
Fig. 6 Servicing Fuel Pressure Regulator
Fig. 7 Removing Injector Cap
Fig. 8 Removing Fuel Injector
Ä FUEL SYSTEMS 14 - 51

(7) Ensure the injector lower O-ring has been re-
moved from the pod (Fig. 9).
INSTALLATION
(1) Apply a light coating of clean engine oil on the
O-rings. (2) Place assembly in the pod. Align the injector
wiring terminals with the injector cap fastener hole
(Fig. 10).
(3) Install injector cap with locating notch aligned
with the locating lobe on the injector (Fig. 11). (4) Push down on the cap to ensure a good seal.
(5) Rotate the cap and injector to line up the at-
tachment hole (Fig. 12).
(6) Install injector cap holddown screw (torx-head
screw). Tighten screw to 4-5 N Im (35-45 in. lbs.) torque.
(7) 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. (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. (9) Reinstall the air cleaner assembly.
THROTTLE POSITION SENSOR
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove air cleaner.
(3) Disconnect harness connector from throttle po-
sition sensor (Fig. 13). (4) Remove throttle position sensor mounting
screws. (5) Remove throttle position sensor from throttle
shaft.
INSTALLATION
(1) Install throttle position sensor to throttle body,
position toward the front of the vehicle. Tighten
screws to 2 N Im (20 in. lbs.) torque.
(2) Connect 3 way connector at throttle position
sensor.
Fig. 9 Servicing Fuel Injector
Fig. 10 Fuel Injector Installation
Fig. 11 Installing Fuel Injector Cap
Fig. 12 Fuel Injector Installed
14 - 52 FUEL SYSTEMS Ä

METHANOL CONCENTRATION SENSORÐPCM
INPUT
The methanol concentration sensor contains a mi-
croprocessor that determines the percentage of gaso-
line and methanol in the fuel system. From the
methanol concentration sensor input, the powertrain
control module (PCM) determines the amount of
methanol in the fuel. The vehicle can operate on a
mixtures up to 85 percent methanol, 15 percent gas-
oline. The PCM supplies 8 volts to the methanol concen-
tration sensor. The methanol concentration sensor
output voltages varies with the percent of methanol
in the fuel system. The sensor output voltage (input
for PCM) ranges from 0.5 volts for pure gasoline to
4.50 volts for 85 percent methanol. For two seconds
at key ON when the operator starts the vehicle, the
sensor calibrates the PCM. During the calibration
period the sensor sends 4.45 volts to the PCM as a
correction factor. The methanol concentration sensor has a built-in
shutdown capability. If the sensor shuts down, the
PCM defaults to the previous learned value (output
voltage based on methanol percentage of fuel). The methanol concentration sensor attaches to a
bracket at the rear of the fuel tank, next to the fuel
filler tube (Fig. 6).
HEATED OXYGEN SENSOR (O2SENSOR)ÐPCM
INPUT
The heated oxygen sensor is located in the exhaust
manifold. The sensor provides an input voltage to the
PCM (Fig. 7). The input tells the PCM the oxygen
content of the exhaust gas. The PCM uses this infor-
mation to fine tune the air-fuel ratio by adjusting in-
jector pulse width. Flexible fuel vehicles operate on mixtures of fuel
that contain up to 85 percent methanol and 15 per-
cent unleaded gasoline. Different percentages of
methanol in the fuel require different air/fuel ratios. The methanol concentration sensor inputs tells the
PCM what percentage of methanol is in the fuel. The
PCM calculates the ideal air/fuel ratio from the
methanol concentration sensor input. The heated ox-
ygen sensor input tells the PCM if it has reached the
desired air/fuel ratio.
The O
2sensor produces voltages from 0 to 1 volt,
depending upon the oxygen content of the exhaust
gas in the exhaust manifold. When a large amount of
oxygen is present (caused by a lean air-fuel mixture),
the sensor produces a low voltage. When there is a
lesser amount present (rich air-fuel mixture) it pro-
duces a higher voltage. By monitoring the oxygen
content and converting it to electrical voltage, the
sensor acts as a rich-lean switch. The oxygen sensor is equipped with a heating ele-
ment that keeps the sensor at proper operating tem-
perature during all operating modes. Maintaining
correct sensor temperature at all times allows the
system to enter into closed loop operation sooner.
Also, it allows the system to remain in closed loop
operation during periods of extended idle.
Fig. 5 Manifold Absolute Pressure (MAP) SensorFig. 6 Methanol Concentration Sensor
Fig. 7 Heated Oxygen Sensor
Ä FUEL SYSTEMS 14 - 59

ter mounting studs (Fig. 12). The top of the solenoid
has the word TOP on it. The solenoid will not oper-
ate unless it is installed correctly.
DATA LINK CONNECTORÐPCM OUTPUT
The data link connector provides the technician
with the means to connect the DRBII scan tool to di-
agnosis the vehicle.
FUEL INJECTORÐPCM OUTPUT
The Fuel Injectors are electric solenoids driven by
the PCM (Fig. 13). Based on sensor inputs, the PCM
determines when and how long the fuel injector
should operate. The amount of time an injector fires
is referred to as injector pulse width. The auto shut-
down (ASD) relay supplies battery voltage to the in-
jector. The PCM supplies the ground path. By
switching the ground path on and off, the PCM ad-
justs injector pulse width.
When the PCM supplies a ground path, a spring
loaded needle or armature lifts from its seat and fuel
flows through the injector orifice. Fuel is constantly supplied to the injector at regu-
lated 380 Kpa (55 psi). Unused fuel returns to the
fuel tank.
GENERATOR FIELDÐPCM OUTPUT
The PCM regulates the charging system voltage
within a range of 12.9 to 15.0 volts. Refer to Group
8A for charging system information.
IDLE AIR CONTROL MOTORÐPCM OUTPUT
The idle speed stepper motor is mounted on the
throttle body and is controlled by the PCM (Fig. 9).
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 from the throttle position sensor, speed
sensor (distributor pick-up coil), coolant temperature
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.
IGNITION COILÐPCM OUTPUT
The PCM provides a ground contact (circuit) for en-
ergizing the ignition coil. When the PCM breaks the
contact, the energy in the coil primary 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. Refer to Auto Shutdown
(ASD) Relay/Fuel Pump RelayÐPCM Output in this
section for relay operation. The ignition coil is mounted on the hot box next to
the thermostat housing (Fig. 14).
MALFUNCTION INDICATOR (CHECK ENGINE)
LAMPÐPCM 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
operator 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
Fig. 13 Fuel Injector
Fig. 14 Ignition Coil
14 - 62 FUEL SYSTEMS Ä