1993 CHEVROLET DYNASTY sensor

2.2L TURBO III, 3.3L AND 3.8L IGNITION SYSTEMÐSYSTEM OPERATION INDEX
page page
Auto Shutdown (ASD) Relay and Fuel Pump Relay ................................ 32
Camshaft Position Sensor .................. 28
Coolant Temperature Sensor ................ 32
Crankshaft Position Sensor ................. 29
General Information ....................... 24 Ignition Coil
............................. 31
Knock SensorÐTurbo III Engine ............. 32
Manifold Absolute Pressure (MAP) Sensor ..... 32
Powertrain Control Module (PCM) ............ 24
Spark Plug Cables ....................... 25
Spark Plugs ............................ 26
GENERAL INFORMATION
This section describes the ignition systems for 2.2L
Turbo III, 3.3L and 3.8L engines. The Fuel Injection sections of Group 14 describe On
Board Diagnostics. Group 0, Lubrication and Maintenance, contains
general maintenance information for ignition related
items. The Owner's Manual also contains maintenance
information. 2.2L Turbo III, 3.3L and 3.8L engines uses a
fixed ignition timing system. Basic ignition tim-
ing is not adjustable. All spark advance is deter-
mined by the powertrain control module (PCM). The ignition system does not use a distributor. The
system is referred to as the Direct Ignition System. The
system's three main components are the coil pack,
crankshaft position sensor, and camshaft position sen-
sor. The crankshaft and camshaft sensors are hall
effect devices. The camshaft position and crankshaft position sen-
sors generate pulses that are the inputs sent to the
PCM. The PCM interprets crankshaft and camshaft
position from these sensors. The PCM uses crankshaft
position sensor input to determine ignition timing. The
PCM determines injector sequence from the camshaft
position sensor. The camshaft position sensor determines when a
slot in the camshaft gear passes beneath it (Fig. 1 or
Fig. 2). The crankshaft position sensor determines
when a window in the drive plate passes under it
(Fig. 3 or Fig. 4). When metal aligns with the sensor,
voltage goes low (less than 0.5 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.
FIRING ORDER
The firing order of the 2.2L Turbo III engine direct
ignition system is 1-3-4-2 (Fig. 5). The firing order of
the 3.3L and 3.8L engines direct ignition system is
1-2-3-4-5-6 (Fig. 6).
POWERTRAIN CONTROL MODULE (PCM)
The ignition system is regulated by the powertrain
control module (PCM) (Fig. 7). The PCM supplies
battery voltage to the ignition coil through the Auto
Shutdown (ASD) Relay. The PCM also controls
ground circuit for the ignition coil. By switching the
ground path for the coil on and off, the PCM adjusts
ignition timing to meet changing engine operating
conditions.
Fig. 37 Manifold Absolute Pressure (MAP) SensorÐ3.0L Engine
8D - 24 IGNITION SYSTEMS Ä

During the crank-start period the PCM advances
ignition timing a set amount. During engine opera-
tion, the amount of spark advance provided by the
PCM is determined by these input factors:
² coolant temperature
² knock sensor (Turbo III)
² engine RPM
² available manifold vacuum
The PCM also regulates the fuel injection system.
Refer to the Fuel Injection sections of Group 14.
SPARK PLUG CABLES
Spark Plug cables are sometimes referred to as sec-
ondary ignition wires. The wires transfer electrical
current from the distributor to individual spark
plugs at each cylinder. The spark plug cables are of
nonmetallic construction and have a built in resis-
Fig. 1 Camshaft SprocketÐ2.2L Turbo III Engine
Fig. 2 Camshaft SprocketÐ3.3L and 3.8L Engines
Fig. 3 DriveplateÐ2.2L Turbo III Engine
Fig. 4 DriveplateÐ3.3L and 3.8L Engines
Fig. 5 Spark Plug Wire RoutingÐTurbo III Engine
Ä IGNITION SYSTEMS 8D - 25

SCAVENGER DEPOSITS Fuel scavenger deposits may be either white or yel-
low (Fig. 12). They may appear to be harmful, but
are a normal condition caused by chemical additives
in certain fuels. These additives are designed to
change the chemical nature of deposits and decrease
spark plug misfire tendencies. Accumulation on the
ground electrode and shell area may be heavy but
the deposits are easily removed. Spark plugs with
scavenger deposits can be considered normal in con-
dition and be cleaned using standard procedures.
CHIPPED ELECTRODE INSULATOR A chipped electrode insulator usually results from
bending the center electrode while adjusting the
spark plug electrode gap. Under certain conditions,
severe detonation also can separate the insulator
from the center electrode (Fig. 13). Spark plugs with
chipped electrode insulators must be replaced.
PREIGNITION DAMAGE
Excessive combustion chamber temperature can
cause preignition damage. First, the center electrode
dissolves and the ground electrode dissolves some- what later (Fig. 14). Insulators appear relatively de-
posit free. Determine if the spark plug has the
correct heat range rating for the engine, if ignition
timing is over advanced or if other operating condi-
tions are causing engine overheating. The heat range
rating refers to the operating temperature of a par-
ticular type spark plug. Spark plugs are designed to
operate within specific temperature ranges depend-
ing upon the thickness and length of the center elec-
trode and porcelain insulator.
SPARK PLUG OVERHEATING
Overheating is indicated by a white or gray center
electrode insulator that also appears blistered (Fig.
15). The increase in electrode gap will be consider-
ably in excess of 0.001 in per 1000 miles of operation.
This suggests that a plug with a cooler heat range
rating should be used. Over advanced ignition tim-
ing, detonation and cooling system malfunctions also
can cause spark plug overheating.
CAMSHAFT POSITION SENSOR
The camshaft position sensor provides fuel injection
synchronization and cylinder identification informa-
Fig. 12 Scavenger Deposits
Fig. 13 Chipped Electrode Insulator
Fig. 14 Preignition Damage
Fig. 15 Spark Plug Overheating
8D - 28 IGNITION SYSTEMS Ä

tion (Fig. 16 or Fig. 17). The sensor generates pulses
that are the input sent to the PCM. The PCM inter-
prets the camshaft position sensor input (along with
the crankshaft position sensor input) to determine
crankshaft position. The PCM uses the crankshaft
position sensor input to determine injector sequence
and ignition timing.
The camshaft position sensor determines when a slot
in the camshaft gear passes beneath it (Fig. 18 or Fig.
19). When metal aligns with the sensor, voltage goes
low (less than 0.5 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. The camshaft position sensor is mounted to the top
of the timing case cover (Fig. 20 or Fig. 21). The bot-
tom of the sensor is positioned above the camshaft
sprocket. The distance between the bottom of
sensor and the camshaft sprocket is critical to
the operation of the system. When servicing the
camshaft position sensor, refer to the Turbo III, 3.3L and 3.8L Ignition SystemÐService Proce-
dures section in this Group.
CRANKSHAFT POSITION SENSOR
The crankshaft position sensor senses slots cut into
the transaxle driveplate extension (Fig. 22 or Fig. 23).
On Turbo III, there ar e a 2 sets of slots. Each set
contains 4 slots, for a total of 8 slots (Fig. 24). On 3.3L
and 3.8L engines, there ar e a 3 sets of slots. Each set
contains 4 slots, for a total of 12 slots (Fig. 25).
Fig. 16 Camshaft Position SensorÐTurbo III Engine
Fig. 17 Camshaft Position SensorÐ3.3L and 3.8L Engines
Fig. 18 Camshaft GearÐTurbo III Engine
Fig. 19 Camshaft GearÐ3.3L and 3.8L Engines
Ä IGNITION SYSTEMS 8D - 29

Basic timing is set by the position of the last slot
in each group. Once the powertrain control module (PCM) senses the last slot, it determines crankshaft
position (which piston will next be at TDC) from the
camshaft position sensor input. The 4 pulses generated
by the crankshaft position sensor represent the 69É,
49É, 29É, and 9É BTDC marks. It may take the PCM one
engine revolution to determine crankshaft position
during cranking.
The PCM uses the camshaft position sensor to deter-
mine injector sequence. The PCM determines igni-
Fig. 20 Camshaft Position Sensor LocationÐTurbo III Engines
Fig. 21 Camshaft Position Sensor LocationÐ3.3Land 3.8L Engines
Fig. 22 Crankshaft Position SensorÐTurbo III Engine
Fig. 23 Crankshaft Position SensorÐ3.3L and 3.8L Engines
Fig. 24 Timing Slots in Transaxle DriveplateÐTurboIII Engine
Fig. 25 Timing Slots in Transaxle DriveplateÐ3.3Land 3.8L Engines
8D - 30 IGNITION SYSTEMS Ä

tion timing from the crankshaft position sensor. Once
crankshaft position has been determined, the PCM
begins energizing the injectors in sequence.On Turbo III engines, the crankshaft position sensor
is located in the transaxle housing, below the throttle
body (Fig. 26). On 3.3L and 3.8L engines, the crank-
shaft position sensor is located in the transaxle hous-
ing (Fig. 27). The bottom of the sensor is positioned next to the
drive plate. The distance between the bottom of
sensor and the drive plate is critical to the op-
eration of the system. When servicing the crank-
shaft sensor, refer to the 3.3L Ignition
SystemÐService Procedures section in this
Group.IGNITION COIL
WARNING: THE DIRECT IGNITION SYSTEM GENER-
ATES APPROXIMATELY 40,000 VOLTS. PERSONAL
INJURY COULD RESULT FROM CONTACT WITH
THIS SYSTEM.
The 3.3L and 3.8L coil assembly consists of 3 coils
molded together (Fig. 28). The assembly is mounted
on the intake manifold. The 2.2L Turbo III coil as-
sembly consists of 2 coils molded together (Fig. 29).
The assembly is mounted at the front of the engine.
For all engines, the number of each coil appears on
the front of the coil pack.
High tension leads route to each cylinder from the
coil. The coil fires two spark plugs every power
stroke. One plug is the cylinder under compression,
the other cylinder fires on the exhaust stroke. The
PCM determines which of the coils to charge and fire
at the correct time. On 3.3L and 3.8L engines, coil one fires cylinders 1
and 4, coil two fires cylinders 2 and 5, coil three fires
cylinders three and six.
Fig. 28 Coil PackÐ2.2L Turbo III Engine
Fig. 29 Coil PackÐ3.3L and 3.8L Engines
Fig. 26 Crankshaft Position Sensor LocationÐTurbo III Engines
Fig. 27 Crankshaft Position Sensor LocationÐ3.3Land 3.8L Engines
Ä IGNITION SYSTEMS 8D - 31

The coil's low primary resistance allows the PCM to
fully charge the coil for each firing.
COOLANT TEMPERATURE SENSOR
On 2.2L Turbo III engines, the coolant temperature
sensor is installed into the thermostat housing (Fig. 30).
On 3.3L and 3.8L engines, the coolant temperature sensor
is located next to the thermostat housing (Fig. 31).
The coolant temperature sensor provides an input
voltage to the powertrain control module (PCM). The
sensor is a variable resistance (thermistor) with a
range of -40ÉC to 130ÉC (-40ÉF to 265ÉF). As coolant
temperature varies, the sensor resistance changes,
resulting in a different input voltage to the PCM.
The PCM contains different spark advance schedules
for cold and warm engine operation. The schedules reduce
engine emission and improve driveability.
The PCM demands slightly richer air-fuel mixtures
and higher idle speeds until the engine reaches normal
operating temperature. The coolant sensor input is also used for cooling
fan control.
KNOCK SENSORÐTURBO III ENGINE
Turbo III engines use a knock sensor. The sensor gen-
erates a signal when spark detonation occurs in the
combustion chambers. The sensor is mounted on the in-
take manifold behind the PCV breather (Fig. 32). The
sensor provides input voltage used by the powertrain
control module (PCM) to modify spark advance and
boost schedules in order to eliminate detonation.
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSOR
The MAP sensor reacts to absolute pressure in the
intake manifold and provides an input voltage to the
powertrain control module (PCM). As engine load
changes, manifold pressure varies. The changes in
engine load cause the MAP output voltage to change.
The change in MAP sensor output voltage results in
a different input voltage to the PCM.
The input voltage level supplies the PCM with infor-
mation relating to ambient barometric pressure during
engine start-up (cranking) and engine load while its op-
erating. The PCM uses this input along with inputs
from other sensors to adjust air-fuel mixture.
On Turbo III engines, the MAP sensor is mounted
to the front right fender (Fig. 33) On 3.3L and 3.8L
engines, the MAP sensor (Fig. 34) is mounted to the
side of the intake manifold, below the positive crank-
case ventilation (PCV) valve. The sensor is connected
to the PCM electrically.
AUTO SHUTDOWN (ASD) RELAY AND FUEL PUMP
RELAY
The powertrain control module (PCM) operates the
auto shutdown (ASD) relay and fuel pump relay
through one ground path. The PCM operates the re-
lays by switching the ground path on and off. Both
relays turn on and off at the same time.
Fig. 32 Knock SensorÐTurbo III Engine
Fig. 30 Coolant Temperature SensorÐTurbo III En- gines
Fig. 31 Coolant Temperature SensorÐ3.3L and 3.8LEngines
8D - 32 IGNITION SYSTEMS Ä

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 camshaft position sen-
sor and crankshaft position sensor signals. From
these inputs, the PCM determines engine speed and
ignition timing (coil dwell). If the PCM does not re-
ceive a camshaft position sensor signal when the ig-
nition switch is in the Run position, it will de-
energize both relays. When the relays are de-
energized, battery voltage is not supplied to the fuel
injector, ignition coil, fuel pump and oxygen sensor
heating element. On AC, AG, AJ and AY models, the ASD relay and
fuel pump relay are located in the power distribution
center (Fig. 35, 36, 37, or 38). On AA and AP models, the ASD relay and fuel
pump relay are mounted on the drivers side fender
well, next to the strut tower (Fig. 39).
Fig. 33 MAP SensorÐTurbo III Engine
Fig. 34 Map SensorÐ3.3L and 3.8L Engines
Fig. 35 Power Distribution Center (PDC) (AC Body)
Fig. 36 Relay Identification (AC Body)
Fig. 37 Power Distribution Center (PDC) (AG and AJ Body)
Ä IGNITION SYSTEMS 8D - 33