check engine CHEVROLET DYNASTY 1993 Service Manual

(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

3.3L AND 3.8L MULTI-PORT FUEL INJECTIONÐSYSTEM OPERATION INDEX
page page
Air Conditioning (A/C) Clutch RelayÐPCM Output. 150
Air Conditioning Switch SenseÐPCM Input .... 147
Auto Shutdown (ASD) Relay and Fuel Pump RelayÐPCM Output .................... 151
Battery VoltageÐPCM Input ............... 147
Brake SwitchÐPCM Input ................. 147
Camshaft Position SensorÐPCM Input ....... 147
Canister Purge SolenoidÐPCM Output ....... 151
CCD Bus .............................. 146
Crankshaft Position SensorÐPCM Input ...... 148
Data Link ConnectorÐPCM Output .......... 152
Electric EGR Transducer (EET) SolenoidÐPCM Output .............................. 152
Engine Coolant Temperature SensorÐPCM Input. 148
Fuel Injectors and Fuel Rail Assembly ........ 155
Fuel InjectorsÐPCM Output ............... 152
Fuel Pressure Regulator .................. 156
Fuel Supply Circuit ...................... 155
General Information ...................... 145
Generator FieldÐPCM Output .............. 150
Heated Oxygen Sensor (O2Sensor)ÐPCM Input. 149
Idle Air Control MotorÐPCM Output ......... 151
Ignition CoilÐPCM Output ................. 153
Malfunction Indicator Lamp (Check Engine Lamp)ÐPCM Output ................... 151
Manifold Absolute Pressure (MAP) SensorÐPCM Input ................................ 149
Modes of Operation ...................... 153
Powertrain Control Module ................. 146
Radiator Fan RelayÐPCM Output ........... 153
Speed Control SolenoidsÐPCM Output ....... 153
Speed ControlÐPCM Input ................ 150
System Diagnosis ....................... 146
TachometerÐPCM Output ................. 153
Throttle Body ........................... 155
Throttle Position Sensor (TPS)ÐPCM Input .... 150
Transaxle Control ModuleÐPCM Output ...... 152
Transaxle Park/Neutral SwitchÐPCM Input .... 150
Vehicle Speed and Distance InputÐPCM Input . 150
GENERAL INFORMATION
3.3L and 3.8L engines use a sequential Multi-port
Electronic 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).
Fig. 1 Multi-Port Fuel Injection Components
Ä FUEL SYSTEMS 14 - 145

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 PCM tests many of its own input and output
circuits. If a fault is found in a major system, the in-
formation is stored in memory. Technicians can dis-
play fault information through the malfunction
indicator lamp (instrument panel Check Engine
lamp) or by connecting the DRBII scan tool. For di-
agnostic trouble code information, refer to the 3.3L/
3.8L Multi-Point 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 engine RPM
and vehicle load information 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 that are
referred to as PCM Outputs. PCM Inputs:
² Air Conditioning Controls
² Battery Voltage
² Brake Switch
² Camshaft Position Sensor
² Crankshaft Position Sensor
² Engine Coolant Temperature Sensor
² Manifold Absolute Pressure (MAP) Sensor
² Oxygen Sensor
² SCI Receive ²
Speed Control System Controls
² Throttle Position Sensor
² Transaxle Park/Neutral Switch (automatic tran-
saxle)
² Vehicle Speed Sensor
PCM Outputs:
² Air Conditioning Clutch Relay
² Generator Field
² Idle Air Control Motor
² Auto Shutdown (ASD) and Fuel Pump Relays
² Canister Purge Solenoid
² Malfunction Indicator Lamp (Check Engine Lamp)
² Data Link Connector
² Electronic EGR Transducer
² Fuel Injectors
² Ignition Coil
² Radiator Fan Relay
² Speed Control Solenoids
² Tachometer Output
Based on inputs it receives, the PCM adjusts the
EGR system, fuel injector pulse width, idle speed, ig-
nition spark advance, ignition coil dwell and canister
purge operation. The PCM regulates the cooling fan,
air conditioning and speed control systems. The PCM
changes generator charge rate by adjusting the gen-
erator field. The PCM adjusts injector pulse width (air-fuel ra-
tio) based on the following inputs.
² battery voltage
² engine coolant temperature
² exhaust gas oxygen content (oxygen sensor)
² engine speed (crankshaft position sensor)
² manifold absolute pressure
² throttle position
The PCM adjusts ignition timing based on the fol-
lowing inputs.
² engine coolant temperature
² engine speed (crankshaft position sensor)
² manifold absolute pressure
² throttle position
Fig. 2 PCM
14 - 146 FUEL SYSTEMS Ä

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

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 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 (Check Engine Lamp) can
also 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 3.3L and 3.8L Multi-Port Fuel
InjectionÐOn-Board Diagnostics section of this Group
for Diagnostic Trouble Code Descriptions.
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
ELECTRIC EGR TRANSDUCER (EET)
SOLENOIDÐPCM OUTPUT
The electronic EGR transducer (EET) contains an
electrically operated solenoid and a back-pressure
transducer (Fig. 16). The PCM operates the solenoid.
The PCM determines when to energize the solenoid.
Exhaust system back-pressure controls the transducer. When the PCM energizes the solenoid, vacuum does
not reach the EGR valve. Vacuum flows to the EGR
valve when the PCM de-energizes the solenoid. When exhaust system back-pressure becomes high
enough, it fully closes a bleed valve in the transducer.
When the PCM de-energizes the solenoid and back-
pressure closes the transducer bleed valve, vacuum
flows through the transducer to operate the EGR valve. De-energizing the solenoid, but not fully closing the
transducer bleed hole (because of by low back- pressure), varies the strength of vacuum applied to
the EGR valve. Varying the strength of the vacuum
changes the amount of EGR supplied to the engine.
This provides the correct amount of exhaust gas re-
circulation for different operating conditions.
FUEL INJECTORSÐPCM OUTPUT
The fuel injectors are electrical solenoids (Fig. 17).
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 needle 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 mani-
fold.
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-
tially energizes all injectors at the same time. Once
Fig. 16 Electric EGR Transducer (EET) Assembly
Fig. 17 Fuel InjectorÐ3.3L Engine
14 - 152 FUEL SYSTEMS Ä

3.3L AND 3.8L MULTI-PORT FUEL INJECTIONÐGENERAL DIAGNOSIS INDEX
page page
Fuel System Diagram .................... 157 Visual Inspection........................ 157
FUEL SYSTEM DIAGRAM
Refer to the Component Identification portion of
this section for a more complete description of the
components shown in Fig. 1.
VISUAL INSPECTION
Perform a visual inspection for loose, disconnected,
or misrouted wires and hoses before diagnosing or
servicing the fuel injection system. A visual check
saves unnecessary test and diagnostic time. A thor-
ough visual inspection includes the following checks: (1) Check ignition cable routing from the coil pack
to the spark plugs. Verify the cable are routed in the
correct order and are fully seated to the coil and
spark plug. (2) Check direct ignition system (DIS) coil electri-
cal connection for damage and a complete connection
to the coil (Fig. 2). (3) Verify the camshaft position sensor electrical
connector is connected to the harness and not dam-
aged (Fig. 3). (4) Ensure the engine temperature sensor electri-
cal connector is connected to the sensor and not dam-
aged (Fig. 3). (5) Ensure the coolant temperature sensor electri-
cal connector is connected to the sensor and not dam-
aged (Fig. 4). (6) Verify the quick connect fuel fittings are fully
inserted on the fuel supply and return tubes. (7) Check the vacuum hose connection at the fuel
pressure regulator for damage or leakage (Fig. 5). (8) Check the oil pressure sending unit electrical
connection (Fig. 6). (9) Verify the electrical connector is attached to
the Purge Solenoid (Fig. 7) and not damaged. (10) Verify the vacuum connection at the purge so-
lenoid is secure and not leaking (Fig. 7).
Fig. 1 Multi-Port Fuel Injection Components
Ä FUEL SYSTEMS 14 - 157

(11) Verify the hoses are securely attached to the
vapor canister (Fig. 8). (12) Ensure the harness connectors for the fuel in-
jector are attached to the correct injector and not
damaged. (13) Verify the fuel injector harness and engine
wiring harness connectors are fully inserted into the
main wiring harness. (14) Check the vacuum connections at the throttle
body (Fig. 9). (15) Ensure the idle air control motor and TPS
electrical connectors are fully seated and not dam-
aged (Fig. 9). (16) Verify the harness connector is attached to
the electric EGR transducer solenoid (Fig. 9). (17) Verify the vacuum connections at the trans-
ducer are secure (Fig. 9). Check all EGR system vac-
uum hoses for secure connections. Inspect the EGR
tube.
Fig. 2 Ignition Coils Electrical Connection
Fig. 3 Camshaft Position Sensor
Fig. 4 Engine Coolant Temperature Sensor
Fig. 5 Fuel Pressure Regulator Vacuum Connection
Fig. 6 Oil Pressure Sending Unit Electrical Connection
14 - 158 FUEL SYSTEMS Ä

(18) Inspect the park/neutral switch wiring connec-
tion for damage. Ensure the automatic transaxle
electrical connections are not damaged (Fig. 10). (19) Check the Vacuum Hose Harness connections
at the Intake Plenum (Fig. 11).
(20) Inspect the PCV system connections for dam-
age (Fig. 12). (21) Inspect the crankshaft position sensor electri-
cal connector for damage (Fig. 13). (22) Ensure the vehicle speed sensor electrical con-
nector is attached to the sensor and not damaged
(Fig. 13). (23) Verify the manifold absolute pressure (map)
sensor electrical connector is attached to the sensor
and not damaged (Fig. 14). (24) Verify the engine ground strap is attached at
the engine (below the MAP sensor) and dash panel
(Fig. 14). Inspect the strap for corrosion or damage.
Fig. 10 Automatic Transaxle Electrical Connections
Fig. 11 Vacuum Hose Connections
Fig. 7 Canister Purge Solenoid
Fig. 8 Vapor Canister
Fig. 9 Throttle Body Electrical and Vacuum Connections
Ä FUEL SYSTEMS 14 - 159

3.3L AND 3.8L MULTI-PORT FUEL INJECTIONÐON-BOARD DIAGNOSTICS INDEX
page page
60-Way Pcm Wiring Connector ............. 167
Circuit Actuation Test Mode ................ 166
Diagnostic Trouble Code Description ......... 163
General Information ...................... 162
High and Low Limits ..................... 163
Monitored Circuits ....................... 162 Non-Monitored Circuits
................... 162
State Display Test Mode .................. 163
System Tests .......................... 163
Throttle Body Minimum Air Flow Check Procedure ............................ 166
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 51 vehicle key on/off cycles. Certain criteria must be met for a diagnostic trou-
ble code to be entered into the PCM memory. The
criteria may be a specific range of engine RPM, en-
gine temperature, and/or input voltage to the PCM. It is possible a diagnostic trouble code for a moni-
tored 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 example, assume
one of the diagnostic trouble code criteria for a sen-
sor circuit is the engine must be operating between
750 and 2000 RPM. 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 diag-
nostic 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 that the
PCM does not monitor and set diagnostic trouble
codes for. Refer to Monitored Circuits and Non-Mon-
itored Circuits in this section. Stored diagnostic trouble codes can be displayed ei-
ther by cycling the ignition key On - Off - On - Off -
On, or through use of the DRBII scan tool. The
DRBII scan tool connects to the data link connector
in the vehicle (Fig. 1).
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. Also, the PCM can determine if the cir-
cuit 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
once the system has entered closed loop. Refer to
Modes of Operation in this section for an explanation
of closed loop operation.
NON-MONITORED CIRCUITS
The powertrain control module (PCM) does not
monitor the following circuits, systems and condi-
tions that could have malfunctions that result in
driveability problems. Diagnostic trouble codes may
not be displayed for these conditions. However, prob-
lems with these systems may cause diagnostic trou-
ble codes to be displayed for other systems. For
example, a fuel pressure problem will not register a
fault directly, but could cause a rich or lean condi-
tion. This could cause an oxygen sensor fault to be
stored in the PCM. Fuel Pressure - Fuel pressure is controlled by the
vacuum assisted fuel pressure regulator. The PCM
cannot detect a clogged fuel pump inlet filter, clogged
in-line fuel filter, or a pinched fuel supply or return
Fig. 1 Powertrain Control Module (PCM)
14 - 162 FUEL SYSTEMS Ä

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