relay CHEVROLET DYNASTY 1993 Workshop Manual

ing, detonation and cooling system malfunctions also
can cause spark plug overheating.
SPARK PLUG SERVICE
When replacing the spark plug and coil cables,
route the cables correctly and secure them in the ap-
propriate retainers. Failure to route the cables prop-
erly can cause the radio to reproduce ignition noise,
cross ignition of the spark plugs or short circuit the
cables to ground.
SPARK PLUG REMOVAL
Always remove the spark plug cable by grasping at
the spark plug boot turning, the boot 1/2 turn and
pulling straight back in a steady motion. (1) Prior to removing the spark plug spray com-
pressed air around the spark plug hole and the area
around the spark plug. (2) Remove the spark plug using a quality socket
with a rubber or foam insert. (3) Inspect the spark plug condition. Refer to
Spark Plug Condition in this section.
SPARK PLUG GAP ADJUSTMENT Check the spark plug gap with a gap gauge. If the
gap is not correct, adjust it by bending the ground
electrode (Fig. 6).
SPARK PLUG INSTALLATION (1) To avoid cross threading, start the spark plug
into the cylinder head by hand. (2) Tighten spark plugs to 28 N Im (20 ft. lbs.)
torque. (3) Install spark plug cables over spark plugs.
POWERTRAIN CONTROL MODULE (PCM)
The ignition system is regulated by the powertrain
control module (PCM) (Fig. 14). The PCM supplies
battery voltage to the ignition coil through the Auto
Shutdown (ASD) Relay. The PCM also controls the
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.
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 engine RPM
² available manifold vacuum
The PCM also regulates the fuel injection system.
Refer to the Fuel Injection sections of Group 14.
DISTRIBUTOR PICK-UPÐPCM INPUT
The engine speed input is supplied to the power-
train control module (PCM) by the distributor pick-
up. The distributor pick-up is a Hall Effect device
(Fig. 15 or Fig. 16).
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 distributor
Fig. 14 Powertrain control module (PCM)
Fig. 15 DistributorÐ2.2L and 2.5L TBI Engines
Fig. 13 Spark Plug Overheating
8D - 6 IGNITION SYSTEMS Ä

to the thermostat housing (Fig. 20). The sensor pro-
vides an input voltage to the powertrain control mod-
ule (PCM). The sensor is a variable resistance
(thermistor) with a range of -40ÉF to 265ÉF. As cool-
ant temperature varies, the sensors resistance
changes, resulting in a different input voltage to the
PCM. The PCM contains different spark advance sched-
ules for cold and warm engine operation. The sched-
ules reduce engine emissions and improve
driveability. Because spark advance changes at dif-
ferent engine operating temperatures during warm-
up, all spark advance testing should be done with the
engine fully warmed. The PCM demands slightly richer air-fuel mixtures
and higher idle speeds until the engine reaches nor-
mal operating temperature. The coolant sensor input is also used for radiator
fan control.
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 causes the MAP sensors 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 in-
formation relating to ambient barometric pressure
during engine start-up (cranking) and engine load
while its operating. The PCM uses this input along
with inputs from other sensors to adjust air-fuel mix-
ture. On 2.2L TBI, 2.5L TBI and 2.5L MPI (flexible fuel
AA-body) engines, the MAP sensor is mounted to the
dash panel (Fig. 21 or Fig. 22). On 3.0L engines, the
sensor is mounted to a bracket across from the dis-
tributor (Fig. 23). The sensor is connected to the
throttle body or intake manifold with a vacuum hose
and 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. 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 distributor pick-up sig-
Fig. 19 Coolant Temperature SensorÐ2.2L TBI, 2.5L TBI and 2.5L MPI Engines
Fig. 20 Coolant Temperature SensorÐ3.0L Engines
Fig. 21 MAP SensorÐ2.2L and 2.5L TBI Engines
8D - 8 IGNITION SYSTEMS Ä

nal. From the pick-up signal, the PCM determines
engine speed and ignition timing (coil dwell). If the
PCM does not receive a distributor signal when the
ignition switch is in the Run position, it will de-en-
ergize both relays. When the relays are de-energized,
battery voltage is not supplied to the fuel injector, ig-
nition coil, fuel pump and oxygen sensor heating el-
ement. On AC, AG, AJ and AY models, the ASD relay and
fuel pump relay are located in the power distribution
center (Fig. 24, 25, 26, or 27). 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. 28).
IGNITION COIL
The 2.2L TBI, 2.5L TBI, 2.5L MPI and 3.0L en-
gines use an epoxy type coil. The coils are not oil
filled. The windings are embedded in a heat and vi-
bration resistant epoxy compound. The powertrain control module (PCM) operates the
ignition coil through the auto shutdown (ASD) relay. When the relay is energized by the PCM, battery
voltage is connected to the ignition coil positive ter-
minal. The PCM will de-energize the ASD relay if it
does not receive an input from the distributor pick-
Fig. 22 MAP SensorÐ2.5L MPI (Flexible Fuel AA-Body) Engines
Fig. 23 MAP SensorÐ3.0L Engine
Fig. 24 Power Distribution Center (PDC) (AC Body)
Fig. 25 Relay Identification (AC Body)
Fig. 26 Power Distribution Center (PDC) (AG and AJ Body)
Ä IGNITION SYSTEMS 8D - 9

up. Refer to Auto Shutdown (ASD) Relay and Fuel
Pump Relay in this section.On 2.2L TBI, 2.5L TBI and 2.5L MPI engines, the
ignition coil is mounted to the thermostat housing
(Fig. 29). On 3.0L engines the coil is mounted on the
rear of the intake manifold next to the air cleaner
(Fig. 30).
Fig. 28 Relay Identification (AA and AP Bodies)
Fig. 29 Ignition CoilÐ2.2L TBI, 2.5L TBI and 2.5L MPI Engines
Fig. 30 Ignition CoilÐ3.0L Engine
Fig. 27 Relay Identification (AG and AJ Body)
8D - 10 IGNITION SYSTEMS Ä

make sure that the spark plugs are firing. Inspect the
distributor rotor, cap, spark plug cables, and spark
plugs. If they are in proper working order, the ignition
system is not the reason why the engine will not start.
Inspect the fuel system and engine for proper opera-
tion.
FAILURE TO START TESTÐ2.5L TBI AND 3.0L
ENGINES
Before proceeding with this test make sure
Testing For Spark At Coil has been performed.
Failure to do this may lead to unnecessary diag-
nostic time and wrong test results.
WARNING: BE SURE TO APPLY PARKING BRAKE
AND/OR BLOCK WHEELS BEFORE PERFORMING
ANY TEST WITH THE ENGINE RUNNING.
(1) Battery voltage must be at least 12.4 volts to
perform test. (2) Crank the engine for 5 seconds while monitoring
the voltage at the coil positive (+) terminal (Fig. 2 or
Fig. 3). If the voltage remains near zero during the
entire period of cranking, refer to Group 14 for On-
Board Diagnostic checks. Also, refer to the DRBII scan
tool and the appropriate Powertrain Diagnostic Proce-
dures manual. These checks will help diagnose prob-
lems with the PCM and auto shutdown relay. (3) If voltage is at near-battery voltage and drops to
zero after 1-2 seconds of cranking, refer to On-Board
Diagnostic in Group 14. Also, refer to the DRBII scan
tool and the appropriate Powertrain Diagnostic Proce-
dures manual. These tests will help check the distribu-
tor reference pickup circuit to the PCM. (4) If voltage remains at near battery voltage during
the entire 5 seconds, with the key off,remove the
PCM 60-way connector. Check the 60-way connector
for any terminals that are pushed out or loose. (5) Remove the connector to coil (+) and connect a
jumper wire between battery (+) and coil (+). (6) Using the special jumper (Fig. 4), momentarily ground terminal #19 of the 60-way connector (Fig.
5). A spark should be generated when the ground is
removed.
(7) If spark is generated, replace the PCM.
(8) If no spark is seen, use the special jumper to
ground the coil (-) terminal directly. (9) If spark is produced, inspect wiring harness for
an open condition.
Fig. 2 Coil TerminalsÐ2.2L TBI, 2.5L TBI and 2.5L MPI Engines
Fig. 3 Coil TerminalsÐ3.0L Engine
Fig. 4 Special Jumper to Ground Coil Negative
Fig. 1 Checking for Spark
8D - 12 IGNITION SYSTEMS Ä

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

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

Fig. 39 Relay Identification (AA and AP Bodies)
Fig. 38 Relay Identification (AG and AJ Body)
8D - 34 IGNITION SYSTEMS Ä

(Fig. 4). Secondary resistance should be 11,600 to
15,800 ohms. Replace the coil if resistance is not
within tolerance.
FAILURE TO START TESTÐTURBO III ENGINE
(1) Determine that sufficient battery voltage (12.4
volts nominal) is present for the cranking and igni-
tion systems. (2) Connect a voltmeter to the wiring harness coil
connector at the B+ pin (Fig. 5).
(3) Crank the engine for 5 seconds while monitor-
ing the voltage at the B+ connector terminal. If the
voltage remains near zero during the entire period of
cranking, check the auto shutdown relay and PCM.
Refer to DRBII scan tool and the appropriate Power-
train Diagnostic Procedures manual. Refer to Group
14 for description of On Board Diagnostics. (4) If voltage is at near-battery voltage, and drops
to zero after 1-2 seconds of cranking, check the cam-
shaft position sensor and crankshaft position sensor
and their circuits. Refer to the DRBII scan tool and
the appropriate Powertrain Diagnostic Procedure
manual. Refer to Group 14 for a description of On-
Board Diagnostics. (5) If voltage remains at near-battery voltage dur-
ing the entire 5 seconds, turn the key off, remove the PCM 60-way connector. Check the 60-way for any
terminals loose from the connector (push-out).
TESTING FOR SPARK AT COILÐ3.3L AND 3.8L
ENGINES
WARNING: THE ENGINE DIRECT IGNITION SYSTEM
GENERATES APPROXIMATELY 40,000 VOLTS. PER-
SONAL INJURY COULD RESULT FROM CONTACT
WITH THIS SYSTEM.
The coil pack contains 3 independent coils. Each coil
must be checked individually.
CAUTION: Spark plug wire damage may occur if the
spark plug is moved more than 1/4 inch away from the
engine ground.
Remove the cable from number 2 spark plug. Insert a
clean spark plug into the spark plug boot, and ground
plug to the engine (Fig. 1). Crank the engine and look for spark across the
electrodes of the spark plug. Repeat the above test for
the five remaining cylinders. If there is no spark
during all cylinder tests, proceed to the failure to start
test. If one or more tests indicate irregular, weak, or no
spark, proceed to Check Coil Test.
WARNING: THE DIRECT IGNITION SYSTEM GENER-
ATES APPROXIMATELY 40,000 VOLTS. PERSONAL
INJURY COULD RESULT FROM CONTACT WITH THIS
SYSTEM.
CHECK COIL TESTÐ3.3L 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. Each coil tower is labeled with the number of the
corresponding cylinder. (1) Remove the ignition cables and measure the
resistance of the cables. Resistance must be between
3,000 to 12,000 ohms per foot of cable. Replace any
cable not within tolerance. (2) Disconnect the electrical connector from the coil
pack (Fig. 6). (3) Measure the primary resistance of each coil. At
the coil, connect an ohmmeter between the B+ pin and
the pin corresponding to the cylinders in question (Fig.
7). Resistance on the primary side of each coil should be
0.5 - 0.7 ohm. Replace the coil if resistance is not within
tolerance. (4) Remove ignition cables from the secondary tow-
ers of the coil. Measure the secondary resistance of the
coil between the towers of each individual coil (Fig. 8).
Refer to the Coil Specifications Chart in the Specifica-
tions section of this group. Replace the coil if resistance
is not within tolerance.
Fig. 4 Checking Ignition Coil Secondary ResistanceÐTurbo III Engines
Fig. 5 Wiring Harness Coil ConnectorÐTurbo III Engine
8D - 36 IGNITION SYSTEMS Ä