light CHEVROLET DYNASTY 1993 Service Manual

² Methanol Concentration Sensor
² Pressure relief/Rollover valve
² PCV Valve
² All fuel system and emission system hoses and
tubes
SYSTEM OPERATION
The flexible fuel vehicle's 2.5L engine use a se-
quential multi-port electronic fuel injection system
(Fig. 1). The powertrain control module (PCM) oper-
ates the electronic fuel injection system. The PCM
provides precise air/fuel ratios and ignition timing
for all driving conditions.
The PCM regulates the air-fuel ratio, ignition coil
dwell and idle speed. The PCM also operates the
high speed and low speed cooling fans, charging sys-
tem, speed control system and various emission con-
trol devices. Various sensors and switches provide inputs to the
PCM. The PCM converts all inputs into signals and
regulates various systems based on the inputs. The
PCM adjusts the systems it controls 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 operates the
injectors in a specific sequence. The PCM adjusts the
air/fuel ratio based on the percentage of methanol in the fuel. The PCM constantly adjusts injector pulse
width to obtain the ideal air fuel ratio for the current
percentage of methanol in the fuel. Injector pulse
width refers to the amount of time an injector oper-
ates. The PCM adjusts injector pulse width by opening
and closing the ground path to the injectors. Engine
RPM (speed), manifold absolute pressure (air density)
and the percentage of methanol in the fuel are the
primary inputs that determine injector pulse width.
SYSTEM DIAGNOSIS
The powertrain control module (PCM) can test
many of its own input and output circuits. If the
PCM senses a fault in a major system, the PCM
stores a diagnostic trouble code in memory. Technicians can display stored diagnostic trouble
codes by two different methods. The first is to cycle
the ignition switch On - Off - On - Off - On within 5
seconds. Then count the number of times the mal-
function indicator 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 between the flashes representing the first and
second digits of the code. Longer pauses separate in-
dividual trouble codes.
Fig. 1 Flexible Fuel MPI Components
14 - 56 FUEL SYSTEMS Ä

A/C clutch relay. To compensate for increased engine
load, the PCM also adjusts idle speed to a scheduled
RPM.
BATTERY VOLTAGEÐPCM INPUT
The powertrain control module (PCM) monitors the
battery voltage input to determine fuel injector pulse
width and generator field control. If battery voltage
is low, the PCM increases injector pulse width to
compensate.
BRAKE SWITCHÐPCM INPUT
When the brake switch activates, the powertrain
control module (PCM) receives an input indicating
that the brakes are being applied. After receiving the
input, the PCM vents the speed control servo. Vent-
ing the servo turns the speed control system off.
ENGINE COOLANT TEMPERATURE SENSORÐPCM
INPUT
The coolant temperature sensor is installed behind
the thermostat housing and ignition coil in the ther-
mostat housing (hot box). The PCM supplies 5 volts
to the coolant temperature sensor. The sensor pro-
vides an input voltage to the PCM (Fig. 3). As cool-
ant temperature varies, the coolant temperature
sensor resistance changes resulting in a different in-
put voltage to the PCM. The PCM demands slightly richer air-fuel mixtures
and higher idle speeds until the engine reaches nor-
mal operating temperature. This sensor is also used for cooling fan control.
CAMSHAFT POSITION SENSORÐPCM INPUT
The camshaft position sensor (distributor pick-up)
supplies engine speed and the injector sync signal to
the powertrain control module (PCM). The sensor is
a Hall Effect device (Fig. 4). A shutter (sometimes referred to as an interrupter)
is attached to the distributor shaft. The shutter con-
tains four blades, one per engine cylinder. A switch plate is mounted to the distributor housing above the
shutter. The switch plate contains the camshaft posi-
tion sensor (distributor pick-up) through which the
shutter blades rotate. As the shutter blades pass
through the pick-up, they interrupt the magnetic
field. The Hall effect device in the pick-up senses the
change in the magnetic field and switches on and off
(which creates pulses), generating the input signal to
the PCM. The PCM calculates engine speed through
the number of pulses generated. One of the shutter blades has a window cut into it.
The window tells the PCM which injector to energize.
MANIFOLD ABSOLUTE PRESSURE (MAP)
SENSORÐPCM INPUT
The powertrain control module (PCM) supplies 5
volts to the MAP sensor. The MAP sensor converts
intake manifold pressure into voltage. The PCM
monitors the MAP sensor output voltage. As vacuum
increases, MAP sensor voltage decreases proportion-
ately. Also, as vacuum decreases, MAP sensor volt-
age increases proportionately. During cranking, before the engine starts running,
the PCM determines atmospheric air pressure from
the MAP sensor voltage. While the engine operates,
the PCM determines intake manifold pressure from
the MAP sensor voltage. Based on MAP sensor volt-
age and inputs from other sensors, the PCM adjusts
spark advance and the air/fuel mixture. The MAP sensor mounts on the dash panel inside
the engine compartment (Fig. 5). A vacuum hose con-
nects the sensor to the throttle body.
Fig. 3 Coolant Temperature Sensor
Fig. 4 Camshaft Position Sensor (Distributor Pick-Up)
14 - 58 FUEL SYSTEMS Ä

2.5L FLEXIBLE FUEL MULTI-PORT FUEL INJECTIONÐON-BOARD DIAGNOSTICS INDEX
page page
Circuit Actuation Test Mode ................. 72
Diagnostic Trouble Codes ................... 71
General Information ....................... 70
High and Low Limits ....................... 71
Ignition Timing Procedure ................... 73 Monitored Circuits
........................ 70
Non-Monitored Circuits ..................... 70
Powertrain Control Module 60-Way Connector . . . 73
State Display Test Mode .................... 72
Throttle Body Minimum Air Flow Check Procedure.. 73
GENERAL INFORMATION
The powertrain control module (PCM) monitors
many different circuits in the fuel injection system. If
the PCM senses a problem with a monitored circuit
often enough to indicate an actual problem, it stores a
diagnostic trouble code in the PCM's memory. If the
problem is repaired or ceases to exist, the PCM cancels
the diagnostic trouble code after 51 vehicle key on/off
cycles. Certain criteria must be met before the PCM stores a
diagnostic trouble code in memory. The criteria may be
a specific range of engine RPM, engine temperature,
and/or input voltage to the PCM. The PCM might not store a diagnostic trouble code
for a monitored circuit even though a malfunction has
occurred. This may happen because one of the diagnos-
tic trouble code criteria for the circuit has not been met.
For example , assume the diagnostic trouble code
criteria for a certain sensor requires the PCM to
monitor the circuit only when the engine operates
between 750 and 2000 RPM. Suppose the sensor's
output circuit shorts to ground when engine operates
above 2400 RPM (resulting in 0 volt input to the PCM).
Because the condition happens at an engine speed
above the maximum threshold (2000 rpm), the PCM
will not store a diagnostic trouble code. There are several operating conditions for which the
PCM monitors and sets diagnostic trouble codes. Refer
to Monitored Circuits and Non-Monitored Circuits in
this section. Technicians can display stored diagnostic trouble
codes by two different methods. The first is to cycle the
ignition switch On - Off - On - Off - On within 5
seconds. Then count the number of times the malfunc-
tion indicator lamp (check engine lamp) on the instru-
ment panel flashes on and off. The number of flashes
represents the trouble code. There is a slight pause
between the flashes representing the first and second
digits of the code. Longer pauses separate individual
trouble codes. The second method of reading diagnostic trouble
codes uses the DRBII scan tool. The DRBII scan tool
connects to the data link (diagnostic) connector in the vehicle (Fig. 1). For diagnostic trouble code informa-
tion, refer to charts in this section.
MONITORED CIRCUITS
The PCM can detect certain fault conditions in the
fuel injection system. Open or Shorted Circuit - The PCM can determine
if the sensor output (input to the PCM) is within proper
range. Also, the PCM can determine open or shorted
circuits. Output Device Current Flow - The PCM senses
whether output devices are hooked up. If a problem
exists within the circuit, the PCM senses whether the
circuit is open, shorted to ground, or shorted high. Heated Oxygen Sensor - Once the system has
entered closed loop, the PCM determines if the oxygen
sensor is switching between rich and lean. Refer to
Modes of Operation in the General Information section
of this group for an explanation of closed loop opera-
tion.
NON-MONITORED CIRCUITS
The PCM does not monitor the following circuits,
systems and conditions that could have malfunctions
causing driveability problems. The PCM might not
store diagnostic trouble codes for these conditions.
However, problems with these systems may cause
Fig. 1 Data Link (Diagnostic) Connector
14 - 70 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

THROTTLE BODY MINIMUM AIR FLOW CHECK
PROCEDURE
(1) Warm engine in Park or neutral until the cooling
fan has cycled on and off at least once. (2) Hook-up timing check device and Tachometer.
(3) Disconnect the coolant temperature sensor and
set basic timing to 12É BTDC 62É BTDC.
(4) Shut off engine. Connect harness connector to
coolant temperature sensor. (5) Disconnect the PCV valve hose from the nipple
on the intake manifold. (6) Attach Air Metering Fitting #6457 (0.125 in.
orifice) to the intake manifold PCV nipple (Fig. 2).
(7) Connect DRBII scan tool to the data link connec-
tor. The connector is located next to the powertrain
control module (PCM) (Fig. 1). (8) Restart engine. Allow engine to idle for at least
one minute. (9) Using the DRBII scan tool, access Min. Airflow
Idle Spd. The following will then occur:
² idle air control motor fully closes ²
Idle spark advance becomes fixed
² The DRBII scan tool displays engine RPM
(10) Check idle RPM with tachometer, if idle RPM is
within the specifications then the throttle body mini-
mum airflow is set correctly.
If the idle RPM is not within specification, replace
the throttle body. (11) Shut off engine.
(12) Remove Air Metering Fitting #6457 from the
intake manifold PCV nipple. Reinstall the PCV valve
hose. (13) Remove DRBII scan tool.
(14) Disconnect timing light and tachometer.
IGNITION TIMING PROCEDURE
Refer to Group 8D Ignition System.
POWERTRAIN CONTROL MODULE 60-WAY CON-
NECTOR
Check the powertrain control module (PCM) 60-way
connector for the following.
² Spread terminals
² Stretched or pulled out wires
² Undertightened or overtightened 60 way connector
Tighten the PCM connector to 4 N Im (35 in. lbs.)
torque. When checking terminal pin outs, refer to the
Powertrain Control Module 60-Way Connector Dia-
gram for circuit wire colors and cavity numbers.
Fig. 2 Checking Minimum Air Flow Using Special Tool 6457
IDLE SPECIFICATIONS
Ä FUEL SYSTEMS 14 - 73

(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) Disconnect oxygen sensor electrical connector.
(2) Remove sensor using Tool C-4907 (Fig. 17).
Slightly tightening the sensor can ease removal. When the sensor is removed, the exhaust manifold
threads must be cleaned with an 18 mm X 1.5 + 6E tap.
If using original sensor, coat the threads with Loctite
771-64 anti-seize compound or equivalent. New sen-
sors are packaged with compound on the threads and
do not require additional compound. The sensor must
be tightened to 28 N Im (20 ft. lbs.) torque.
2.2L TURBO III MULTI-PORT FUEL INJECTIONÐSYSTEM OPERATION
INDEX
page page
Air Conditioning Clutch RelayÐPCM Output .... 89
Air Conditioning Switch SenseÐPCM Input ..... 85
Auto Shutdown (ASD) Relay and Fuel Pump RelayÐPCM Output ..................... 89
Barometric Read SolenoidÐPCM Output ....... 90
Battery VoltageÐPCM Input ................ 85
Brake SwitchÐPCM Input .................. 85
Camshaft Position SensorÐPCM Input ........ 85
Canister Purge SolenoidÐPCM Output ........ 90
CCD Bus .............................. 84
Charge Air Temperature SensorÐPCM Input . . . 86
Crankshaft Position SensorÐPCM Input ....... 87
Data Link ConnectorÐPCM Output ........... 91
Engine Coolant Temperature SensorÐPCM Input . 86
Fuel InjectorÐPCM Output ................. 91
Fuel Injectors and Fuel Rail Assembly ......... 94
Fuel Pressure Regulator ................... 94
Fuel Supply Circuit ....................... 94
General Information ....................... 83
Generator FieldÐPCM Output ............... 89 Heated Oxygen Sensor (O
2Sensor)ÐPCM Input . 88
Idle Air Control MotorÐPCM Output .......... 90
Ignition CoilÐPCM Output .................. 91
Knock SensorÐPCM Input ................. 87
Malfunction Indicator Lamp (Check Engine)ÐPCM Output ............................... 90
Manifold Absolute Pressure (Map) SensorÐPCM Input ................................ 87
Modes of Operation ....................... 92
Powertrain Control Module ................. 84
Radiator Fan RelayÐPCM Output ............ 91
Speed Control SolenoidsÐPCM Output ........ 91
Speed ControlÐPCM Input ................. 88
System Diagnosis ........................ 84
TachometerÐPCM Output .................. 91
Throttle Body ............................ 94
Throttle Position Sensor (TPS)ÐPCM Input ..... 88
Vehicle Speed SensorÐPCM Input ........... 89
Wastegate Control SolenoidÐPCM Output ..... 91
GENERAL INFORMATION
The turbocharged multi-port electronic fuel injec-
tion system combines an electronic fuel and spark
advance control system with a turbocharged intake
system (Fig. 1). The fuel injection system is con-
trolled by the powertrain control module (PCM). The PCM regulates ignition timing, air-fuel ratio,
emission control devices, cooling fan, charging sys-
tem, speed control, turbocharger wastegate and idle
speed. The PCM adapts its requirement to meet
changing operating conditions. Various sensors provide the inputs necessary for
the PCM to correctly regulate fuel flow at the fuel
injector. These include the manifold absolute pres-
sure, throttle position, oxygen sensor, coolant tem-
perature, detonation, and vehicle speed sensors. In
addition to the sensors, the air conditioning clutch
switch and various relays provide important informa-
tion and system control. The outputs include the auto
shutdown relay and fuel pump relay. All inputs to the PCM are converted into signals.
Based on these inputs the PCM adjusts air-fuel ratio,
ignition timing, turbocharger wastegate and other
Fig. 16 Heated Oxygen Sensor
Fig. 17 Oxygen Sensor Socket
Ä FUEL SYSTEMS 14 - 83

The camshaft position sensor senses when a notch in
the camshaft gear passes beneath it (Fig. 4). When
metal aligns with the sensor, voltage goes low (less
than 0.3 volts). When a notch aligns with the sensor,
voltage spikes high (5.0 volts). As a group of notches
pass under the sensor, the voltage switches from low
(metal) to high (notch) then back to low. The number of
notches determine the amount of pulses. If available,
an oscilloscope can display the square wave patterns of
each timing events. Top dead center (TDC) does not occur when notches
on the camshaft sprocket pass below the cylinder. TDC
occurs after the camshaft pulse (or pulses) and after
the 4 crankshaft pulses associated with the particular
cylinder.
The camshaft position sensor is mounted on the top
of the cylinder head (Fig. 5). The bottom of the sensor
is positioned above the camshaft sprocket. The dis-
tance between the bottom of sensor and the
camshaft sprocket is critical to the operation of
the system. When servicing the camshaft posi-
tion sensor, refer to the 2.2L Turbo III Multi-Port
Fuel InjectionÐService Procedures section in
this Group.
CHARGE AIR TEMPERATURE SENSORÐPCM IN-
PUT
The charge air temperature sensor is mounted to
intake manifold. The sensor measures the temperature
of the air-fuel mixture (Fig. 6). This information is used
by the PCM to modify air/fuel mixture and turbo-
charger boost level.
ENGINE COOLANT TEMPERATURE SENSORÐPCM
INPUT
The coolant temperature sensor is a variable resis-
tor with a range of -40ÉC to 128ÉF (-40ÉF to 265ÉF).
The sensor is installed into the thermostat housing
(Fig. 7). The PCM supplies 5.0 volts to the coolant temper-
ature sensor. The sensor provides an input voltage to
the PCM. The PCM determines engine operating
temperature from this input. As coolant temperature
varies, the sensor resistance changes resulting in a
different input voltage to the PCM. Based on the coolant sensor and charge air temper-
ature sensor inputs the PCM changes certain operat-
ing schedules until the engine reaches operating
temperature. While the engine warms up, the PCM
demands slightly richer air-fuel mixtures, lower
boost levels, revised spark advance and higher idle
speeds.
Fig. 5 Camshaft Position Sensor Location
Fig. 6 Charge Air Temperature Sensor
Fig. 4 Camshaft Gear
14 - 86 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

HEATED OXYGEN SENSOR (O2SENSOR)
The oxygen sensor is installed in the exhaust man-
ifold (Fig. 16).
CAUTION: Do not pull on the oxygen sensor wires
when disconnecting the electrical connector.
WARNING: THE EXHAUST MANIFOLD MAY BE EX-
TREMELY HOT. USE CARE WHEN SERVICING THE
OXYGEN SENSOR. (1) Disconnect oxygen sensor electrical connector.
(2) Remove sensor using Tool C-4907 (Fig. 17).
Slightly tightening the sensor can ease removal.
When the sensor is removed, the exhaust manifold
threads must be cleaned with an 18 mm X 1.5 + 6E
tap. If using original sensor, coat the threads with
Loctite 771-64 anti-seize compound or equivalent.
New sensors are packaged with compound on the
threads and do not require additional compound.
Tighten the sensor to 27 N Im (20 ft. lbs.) torque.
Fig. 14 Solenoid Mounting
Fig. 15 PCM
Fig. 16 Heated Oxygen Sensor
Fig. 17 Oxygen Sensor Socket
14 - 112 FUEL SYSTEMS Ä