battery CHEVROLET DYNASTY 1993 Service Manual

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 knock sensor
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 provides a ground path for the injectors to
precisely control injector pulse width. The PCM adjusts
engine idle speed and ignition timing. The PCM con-
trols the air/fuel ratio according to the oxygen content
in the exhaust gas.
ACCELERATION MODE
This is a CLOSED LOOP mode. The PCM recognizes
an abrupt increase in throttle position or MAP pres-
sure 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 deceleration
the following inputs are received by the PCM:
² engine coolant temperature
² knock sensor
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 may receive a closed throttle input from
the throttle position sensor (TPS) at the same time it
senses an abrupt decrease in manifold pressure. This
indicates a hard deceleration. The PCM modifies the
injector sequence. This helps maintain better control
of the air-fuel mixture.
WIDE OPEN THROTTLE MODE
This is an OPEN LOOP mode. During wide-open-
throttle operation, the following inputs are received
by the PCM:
² engine coolant temperature
² knock sensor
² manifold absolute pressure
² engine speed (crankshaft position sensor)
² throttle position
When the PCM senses a wide open throttle condi-
tion it will de-energize the air conditioning relay.
This disables the air conditioning system. The exhaust gas oxygen content input is not ac-
cepted by the PCM during wide open throttle opera-
tion. The PCM will enrichen the air/fuel ratio to
increase performance and compensate for increased
combustion chamber temperature.
IGNITION SWITCH OFF MODE
This is an OPEN LOOP mode. When the ignition
switch is turned to the OFF position, the following
occurs:
² All outputs are turned off.
² No inputs are monitored.
² The PCM shuts down.
Fig. 20 Throttle Body
Ä FUEL SYSTEMS 14 - 93

(15) Inspect the engine and fuel injector harness to
main harness electrical connections. (16) Verify that all electrical connectors are fully
inserted into relays and that battery connections are
clean and tight (Fig. 11).
(17) Check the 60-way electrical connection at the
PCM for damage or spread terminals. Verify that the
60-way connector is fully inserted into the socket on
the PCM (Fig. 12). Ensure that wires are not
stretched or pulled out of the connector.
(18) Verify the harness connector is attached to
idle air control motor (Fig. 13). (19) Verify the harness connector is attached to
the throttle position sensor (Fig. 13). (20) Inspect the hose connections at throttle body
(Fig. 13). (21) Verify all hose connections at the intake man-
ifold are secure (Fig. 14). (22) Check vacuum hose connection between vac-
uum source and fuel pressure regulator (Fig. 15). (23) Inspect the charge air temperature sensor
electrical connector (Fig. 15).
Fig. 8 Camshaft Position Sensor Electrical Connection
Fig. 9 Coolant Temperature and EngineTemperature Sensor
Fig. 10 Power Brake Booster and Speed Control Vacuum Hose Connections
Fig. 11 Power Distribution Center
Fig. 12 PCM Electrical Connector
Ä FUEL SYSTEMS 14 - 97

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

Wastegate Duty Cycle
Battery Temperature
Map Sensor Voltage
Vehicle Speed
Oxygen Sensor State
Baro Read Update
MAP Gauge Reading
Throttle Opening (percentage)
Total Spark Advance
CIRCUIT ACTUATION TEST MODE
The purpose of the circuit actuation test mode is to
check for the proper operation of output circuits or
devices which the powertrain control module (PCM)
cannot internally recognize. The PCM can attempt to
activate these outputs and allow an observer to ver-
ify proper operation. Most of the tests available in
this mode provide an audible or visual indication of
device operation (click of relay contacts, spray fuel,
etc.). With the exception of an intermittent condition,
if a device functions properly during its test, assume
the device, its associated wiring, and its driver cir-
cuit are in working order.
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
Ignition Coil #2
Fuel Injector #1
Fuel Injector #2
Fuel Injector #3
Idle Air Control Motor Open/Close
Radiator Fan Relay
A/C Clutch Relay
Auto Shutdown Relay
Purge Solenoid
S/C Serv Solenoids
Generator Field
Tachometer Output
Wastegate Solenoid
Baro Read Solenoid
All Solenoids/Relays
Speed Control Vent Solenoid
Speed Control Vacuum Solenoid
ASD Fuel System Test
Fuel Injector #4
THROTTLE BODY MINIMUM AIR FLOW CHECK
PROCEDURE
(1) Warm the engine in neutral until the cooling
fan has cycled on and off at least once. (2) Shut off engine.
(3) Hook-up Tachometer.
(4) Disconnect the PCV valve hose from the nipple
on the intake manifold. (5) Attach air metering fitting, special tool 6457
(0.125 inch orifice), to the intake manifold PCV nip-
ple. (6) Disconnect 3/16 inch manifold vacuum purge
line from the top of the throttle body. Cap the 3/16
inch throttle body nipple. (7) Connect DRBII scan tool.
(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 will fully close.
² Idle spark advance will become fixed.
² Engine RPM will be displayed on the DRBII scan
tool. (10) Check idle RPM with tachometer, if idle RPM
is within the below specification then the throttle
body minimum 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 in-
take manifold PCV nipple. Connect the PCV hose to
the nipple. (13) Remove DRBII scan tool.
(14) Disconnect tachometer.
(15) Reconnect purge line to throttle body.
IGNITION TIMING PROCEDURE
Ignition timing cannot be changed or set on the
Turbo III engine. Refer to Group 8D for a description
of the Direct Ignition System (DIS).
60-WAY PCM WIRING CONNECTOR
Refer to the PCM wiring connector diagram (Fig.
2) for information regarding wire colors and cavity
numbers.
IDLE SPECIFICATIONS
Ä FUEL SYSTEMS 14 - 105

2.2L TURBO III MULTI-PORT FUEL INJECTIONÐSERVICE PROCEDURES INDEX
page page
Fuel Injector Rail Assembly ................ 109
Fuel Injectors .......................... 110
Fuel Pressure Regulator .................. 111
Fuel System Pressure Release Procedure ..... 107
Heated Oxygen Sensor (O
2Sensor) ......... 112
Idle Air Control Motor .................... 108
Manifold Absolute Pressure (MAP) Sensor Service .............................. 111 PCM Service
........................... 111
Throttle Body ........................... 107
Throttle Body Removal ................... 108
Throttle Position Sensor (TPS) ............. 107
Wastegate and Canister Purge Solenoid Service . 111
THROTTLE BODY
When servicing throttle body components, always
reassemble components with new O-rings and seals
where applicable (Fig. 1). Never use lubricants on
O-rings or seals, damage may result. If assembly of
component is difficult, use water to aid assembly.
Use care when removing hoses to prevent damage to
hose or hose nipple.
FUEL SYSTEM PRESSURE RELEASE PROCEDURE
CAUTION: The fuel system is under a constant
pressure of approximately 380 kPa (55 psi). Before
servicing the fuel pump, fuel lines, fuel filter, throt-
tle body, or fuel injectors, the fuel system pressure
must be released.
(1) Disconnect negative cable from battery.
(2) Remove fuel filler cap. (3) Remove the protective cap from the fuel pres-
sure test port on the fuel rail (Fig. 2). (4) Place the open end of fuel pressure release
hose, tool number C-4799-1, into an approved gaso-
line container. Connect the other end of hose
C-4799-1 to the fuel pressure test port. Fuel pressure
will bleed off through the hose into the gasoline con-
tainer. Fuel gauge C-4799-A contains hose C-4799-1. (5) Continue fuel system service.THROTTLE POSITION SENSOR (TPS)
REMOVAL
(1) Disconnect the negative cable from the battery.
(2) Disconnect harness connector from throttle po-
sition sensor (Fig. 3). (3) Remove throttle position sensor mounting
screws. (4) Lift throttle position sensor off throttle shaft.
Fig. 1 Throttle Body
Ä FUEL SYSTEMS 14 - 107

INSTALLATION
(1) Install throttle position sensor on throttle shaft.
Install mounting screws. Tighten screws to 2 N Im (17
in. lbs.) torque. (2) Attach harness connector to sensor.
(3) Connect negative cable to negative post of the
battery.
IDLE AIR CONTROL MOTOR
REMOVAL
(1) Disconnect negative cable from battery.
(2) Disconnect harness connector from idle air con-
trol motor (Fig. 4). (3) Remove idle air control motor mounting screws.
(4) Remove the motor from throttle body. Ensure the
O-ring is was removed with the idle air control motor.
INSTALLATION
(1) New idle air control motors have a new O-ring
installed on them. If pintle measures more than 1 inch (25 mm) it must be retracted by using the IDLE
AIR CONTROL MOTOR OPEN/CLOSE mode of the
DRBII scan tool. (2) Carefully place idle air control motor into
throttle body. (3) Install mounting screws. Tighten screws to 2
N Im (17 in. lbs.) torque.
(4) Connect harness connector to motor.
(5) Connect negative cable to battery.
THROTTLE BODY REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove clamp from air hose. Remove hose (Fig.
5). (3) Remove accelerator cable.
(4) Disconnect idle air control motor and throttle
position sensor (TPS) electrical connectors (Fig. 6). (5) Disconnect vacuum hoses from throttle body.
(6) Remove throttle body to intake manifold at-
taching nuts (2). (7) Remove throttle body and gasket.
INSTALLATION
(1) Install throttle body with new gasket.
(2) Install throttle body attaching nuts. Tighten
nuts to 25 N Im (225 in. lbs.) torque.
(3) Connect vacuum hoses to the throttle body.
(4) Attach harness connectors to the throttle posi-
tion sensor (TPS) and the idle air control motor. (5) Install throttle and speed control cables (if ap-
plicable). (6) Install throttle body intake air hose. Tighten
clamp to 4 N Im (30 in. lbs.) torque.
(7) Connect negative cable to battery.
Fig. 4 Idle Air Control MotorFig. 2 Fuel Pressure Test Port
Fig. 3 Throttle Position Sensor
14 - 108 FUEL SYSTEMS Ä

FUEL INJECTOR RAIL ASSEMBLY
WARNING: THE 2.2L TURBO III FUEL SYSTEM IS
UNDER A CONSTANT PRESSURE OF APPROXI-
MATELY 380 KPA (55 PSI). PERFORM FUEL PRES-
SURE RELEASE PROCEDURE BEFORE SERVICING
THE FUEL RAIL OR FUEL INJECTORS.
REMOVAL
(1) Perform fuel system pressure release procedure.
(2) Disconnect negative battery cable.
CAUTION: Place a shop towel should under the fuel
hoses to catch any fuel spillage. (3) Remove quick connect fittings from the chassis
fuel tubes (Fig. 7). Refer to Quick Connect Fittings
in the Fuel Delivery Section of this manual.
(4) Disconnect the vacuum hose from the fuel pres-
sure regulator (Fig. 8). (5) Disconnect the fuel injector wiring harness
from the main harness. (6) Place oil separator bracket out of the way and
remove the fuel rail support bracket screws.
(7) Remove the fuel rail and injector assembly by
pulling rail so that the injectors come straight out of
their ports. Do not damage the rubber injector
O-rings after removing the fuel rail. Do not remove fuel injectors until fuel rail assem-
bly has been completely removed from the vehicle.
Fig. 7 Quick Connect Fittings
Fig. 8 Fuel Rail Fasteners
Fig. 5 Air Cleaner Assembly
Fig. 6 Throttle Body Assembly
Ä FUEL SYSTEMS 14 - 109

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

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

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