fuel CHEVROLET DYNASTY 1993 Workshop Manual

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

mal wear can usually be cleaned, have the electrodes
filed and regapped, and then reinstalled. Some fuel refiners in several areas of the United
States have introduced a manganese additive (MMT)
for unleaded fuel. During combustion, fuel with MMT
may coat the entire tip of the spark plug with a rust
colored deposit. The rust color deposits can be misdi-
agnosed as being caused by coolant in the combustion
chamber. Spark plug performance is not affected by
MMT deposits.
COLD FOULING (CARBON FOULING) Cold fouling is sometimes referred to as carbon
fouling because the deposits that cause cold fouling are
basically carbon (Fig. 9). A dry, black deposit on one or
two plugs in a set may be caused by sticking valves or
defective spark plug cables. Cold (carbon) fouling of the
entire set may be caused by a clogged air cleaner. Cold fouling is normal after short operating periods.
The spark plugs do not reach a high enough operating
temperature during short operating periods.
WET FOULING A spark plug that is coated with excessive wet fuel or
oil is wet fouled. In older engines, wet fouling can be
caused by worn rings or excessive cylinder wear.
Break-in fouling of new engines may occur be-
fore normal oil control is achieved. In new or
recently overhauled engines, wet fouled spark
plugs can be usually be cleaned and reinstalled.
OIL OR ASH ENCRUSTED If one or more plugs are oil or oil ash encrusted,
engine oil is entering the combustion chambers (Fig.
10). Evaluate the engine to determine the cause.
HIGH SPEED MISS When replacing spark plugs because of a high speed
miss condition; wide open throttle operation
should be avoided for approximately 80 km (50 miles) after installation of new plugs.
This will
allow deposit shifting in the combustion chamber to
take place gradually and avoid plug destroying splash
fouling shortly after the plug change.
ELECTRODE GAP BRIDGING
Loose deposits in the combustion chamber can cause
electrode gap bridging. The deposits accumulate on the
spark plugs during continuous stop-and-go driving.
When the engine is suddenly subjected to a high torque
load, the deposits partially liquefy and bridge the gap
between the electrodes (Fig. 11). This short circuits the
electrodes. Spark plugs with electrode gap bridging can
be cleaned using standard procedures.
Fig. 9 Normal Operation and Cold (Carbon) Fouling
Fig. 10 Oil or Ash Encrusted
Fig. 11 Electrode Gap Bridging
Ä IGNITION SYSTEMS 8D - 27

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

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

INSTRUMENT PANEL AND GAUGES
CONTENTS
page page
AA BODY .............................. 1
AC AND AY BODIES .................... 23 AG AND AJ BODIES
.................... 42
AP BODY ............................. 58
AA BODY INDEX
page page
Cluster and Gauge Service and Testing ........ 2
Electronic Cluster ........................ 13
Fuel GaugeÐFlexible Fuel .................. 2
Gauges ................................. 7
General Information ........................ 1 Instrument Panel
......................... 21
Interior Lamp Replacement ................. 21
Mechanical/Electronic Cluster Removal ......... 5
Switch and Panel Component Service ......... 15
GENERAL INFORMATION
INSTRUMENT CLUSTERS
There are three instrument cluster assemblies. The
mechanical clusters incorporate magnetic type
gauges. The electronic instrument cluster incorpo-
rates, a digital speedometer/odometer and electronic
analog gauges. The mechanical Lo-Line instrument cluster has
magnetic type gauges for coolant temperature, fuel
level and charging system voltage (Fig. 1).
The mechanical Hi-Line instrument cluster has
magnetic type gauges for oil pressure, coolant tem-
perature, charging system voltage and fuel level. The
premium instrument cluster also has a tachometer
(Fig. 2). If the ignition switch is in the OFF position each
gauge will show a reading, except for the volt gauge. However the readings are only accurate when the ig-
nition switch is in the ON position.
TACHOMETER DRIVE MODULE
The tachometer drive module is an electronic mod-
ule used to drive a magnetic tachometer in a conven-
tional instrument cluster.
ELECTRONIC DIGITAL CLOCK
The electronic digital clock is in the radio. The
clock and radio each use the display panel built into
the radio. A digital readout indicates the time in
hours and minutes whenever the ignition switch is in
the ON or ACC position. When the ignition switch is in the OFF position, or
when the radio frequency is being displayed, time
keeping is accurately maintained.
MESSAGE CENTER
The message center includes the graphic display of
the car with illuminating graphics for: low wind-
Fig. 1 Instrument Cluster
Fig. 2 Instrument Cluster With Tachometer
Ä INSTRUMENT PANEL AND GAUGES 8E - 1

shield washer fluid, door ajar for each door, and
trunk ajar. It also includes headlamp out, tail lamp
out, and brake lamp out warning lights (Fig. 3),
these lights are operated by a lamp outage module.
When there is no message center there is no door
ajar function.
TRAVELER
The traveler is a five function trip computer. It
uses vacuum fluorescent displays to display: trip
miles, instantaneous fuel economy, trip elapsed time,
trip average fuel economy and, estimate distance to
empty. It is located in the message center (Fig. 4).
WARNING LAMPS AND INDICATOR LIGHTS
The mechanical instrument cluster assemblies
have warning lamps and indicator lights for ten dif-
ferent systems. These include left and right turn sig-
nals, low fuel level, low oil pressure, high beam indicator, seat belt reminder, brake system, malfunc-
tion indicator (check engine) lamp, check gauges, an-
ti-lock system and air bag system indicator. The low oil pressure indicator replaces the Check
Gauges indicator in the cluster assembly without a
tachometer. In the cluster assembly with tachometer, Check
Gauges indictor illuminates in a warning situation.
This will notify driver to check for a problem in cool-
ant temperature, oil pressure or electrical systems.
CLUSTER AND GAUGE SERVICE AND TESTING
CAUTION: Disconnect battery cable. Before servic-
ing the instrument panel. Reconnect battery cable
when power is required for test purposes.
FUEL GAUGEÐFLEXIBLE FUEL
The flexible fuel vehicle uses a dampened fuel
gauge. Methanol fuel causes erratic gauge movement
if the proper gauge is not used. The unique fuel gauge may be identified by either
a green logo on the face of the gauge or by checking
the part number. Remove cluster from the instru-
ment panel and check the part number on top of the
cluster. Refer to Mechanical/Electronic Cluster Re-
moval for proper procedures. Refer to parts catalog
for proper part number.
Fig. 3 Message Center
Fig. 4 Traveler and Message Center
8E - 2 INSTRUMENT PANEL AND GAUGES Ä

SENDING UNIT TEST
When a problem occurs with a cluster gauge, be-
fore disassembling the cluster to check the gauge,
check for a defective sending unit or wiring. (1) Sending units and wiring can be checked by
grounding the connector leads, at the sending unit,
in the vehicle. (2) With the ignition in the ON position; a
grounded input will cause the oil, fuel or tempera-
ture gauge to read at or above maximum.
LOW OIL PRESSURE/CHECK GAUGES WARNING LAMP TEST
The low oil pressure/check gauges warning lamp
will illuminate when the ignition key is turned to
the ON position without starting the vehicle. In the cluster assembly without tachometer, the
low oil pressure lamp will illuminate if the engine oil
pressure drops below a safe oil pressure level. In the cluster assembly with tachometer, the Check
Gauges warning lamp illuminates when there is a
problem in oil pressure level, high engine tempera-
ture or low voltage. To test the system turn ignition key to the ON po-
sition. If the lamp fails to light, inspect for a broken
or disconnected wire at the oil pressure combination
unit, which is located at the front of the engine (Figs.
5 and 6). If the wire at the connector checks good,
pull connector loose from the switch terminal and
with a jumper wire ground connector to the engine
(Fig. 7). With the ignition key turned to the ON po-
sition check the warning lamp. If lamp still fails to
light, inspect for a burned out lamp or disconnected
socket in the cluster.
COMBINATION OIL UNIT TEST
The combination oil unit has two functions:
(1) The normal closed circuit keeps the oil pressure
warning/check gauges lamp on until there is oil pres-
sure (Fig. 7). (2) The sending unit provides a resistance that
varies with oil pressure. (3) To test the normally closed oil lamp circuit, dis-
connect the locking connector and measure the resis-
tance between the switch terminal and the metal
housing. The ohmmeter should read 0 ohms. Start
the engine. (4) If there is oil pressure, the ohmmeter should
read an open circuit. (5) To test the sending unit, measure the resis-
tance between the sending unit terminal and the
metal housing. The ohmmeter should read open.
Start the engine. (6) The ohmmeter should read between 30 to 55
ohms, depending on engine speed, oil temperature,
and oil viscosity. (7) If the above results are not obtained, replace
the switch.
BRAKE SYSTEM WARNING LAMP TEST
The brake warning lamp illuminates when parking
brake is applied with ignition key turned ON. The
same lamp will also illuminate should one of the two
service brake systems fail when brake pedal is ap-
plied. To test system turn ignition key ON, and ap-
ply parking brake. If lamp fails to light, inspect for a
burned out lamp, disconnected socket, a broken orFig. 5 Combination Oil Unit (2.5L)
Fig. 6 Combination Oil Unit (3.0L)
Fig. 7 Combination Oil Unit Test
Ä INSTRUMENT PANEL AND GAUGES 8E - 3

(a) Route transmission range indicator guide as-
sembly under left steering column wing and down
left side of column (Fig. 12). (b) Insert flange of column insert into column,
squeeze legs together with tabs under column
jacket and engage lock bar to secure insert (Fig.
14). (c) Hook cable eyelet to steering column actuator
check pointer, should indicate neutral. Do not kink
or bind transmission range indicator guide tube
and position guide tube in original location. (d) Adjust with tool if necessary to center pointer
on N (Neutral) and check in other gears (Fig. 15).
(4) Install upper and lower steering column cover.
(5) Install the rear window defogger bezel and ra-
dio bezel. (6) Install cluster bezel.
(7) Reconnect battery.
REMOVALÐCLUSTER WITHOUT TRANSMISSION RANGE
INDICATOR FROM STEERING COLUMN (1) Remove cluster bezel (Fig. 10).
(2) Remove four screws attaching cluster to base
panel. (3) Pull cluster rearward carefully, reach behind
and disconnect the two harness connectors. (4) Carefully rotate cluster and remove the two
transmission range indicator screws. (5) Remove cluster assembly.
(6) For installation reverse above procedures. (a) Do not kink guide tube when installing clus-
ter. (b) Replace guide tube behind fuse block.
GAUGES
It is not necessary to remove instrument clus-
ter assembly from vehicle for gauge replace-
ment. When removing gauge assemblies from cluster,
gauge must be pulled straight out, not twisted, or
damage to gauge pin may result.
MULTIPLE GAUGE MALFUNCTION
If the fuel, voltage and tachometer gauges appear
to be malfunctioning, remove the cluster assembly.
Check for good pin contact between the wire harness
and printed circuit board. If there is good contact,
check for ignition voltage at ignition cavity C of the
black connector. If there is ignition voltage, check for
continuity between the wire harness ground cavity H
of the black connector and ground. If there is conti-
nuity, replace printed circuit board. If the temperature, oil pressure and speedometer
gauges appear to be malfunctioning remove the clus-
ter assembly. Check for a good contact between the
wire harness and the printed circuit board. If there is
good contact, check for ignition voltage at cavity J of
the red connector. If there is voltage, check for con- tinuity at cavity H of the black connector. If there is
continuity, replace the printed circuit board.
If the temperature, fuel, voltage and speedometer
gauges appear to be malfunctioning, remove the clus-
ter assembly. Check for good pin contact between the
wire harness and the printed circuit board. If there is
good contact, check ignition voltage at cavity J of the
red connector. If there is voltage, check for continuity
at cavity H of the black connector. If there is conti-
nuity, replace the printed circuit board.
GAUGE INOPERATIVE (FIG. 17 THROUGH 23)
(1) Remove gauge in question.
Fig. 17 Fuel Gauge PinsÐWith Tachometer
Fig. 18 Fuel Gauge PinsÐWithout Tachometer
Ä INSTRUMENT PANEL AND GAUGES 8E - 7

(3) When testing temperature, allow the engine to
run until the vehicle reaches a normal operating
temperature. Turn ignition OFF, and remove gauge
from cluster. (a) Testing oil pressure gauge, engine needs to
be running. (b) Measure and record the resistance between
sending unit pin and ground pin of the gauge in
question. Refer to Gauge Calibration. (c) It is important to have the same engine tem-
perature and engine speed when checking temper-
ature and oil pressure gauges position. The time
between gauge position reading and sending unit
measuring should be kept to a minimum. (d) If resistance and gauge position are not sim-
ilar, replace gauge. (e) If OK, test resistance from the sending unit
to the cluster connector. (f) If resistance reading is different, check
printed circuit board for contact to cluster connec-
tor. (g) If OK and contacts are not distorted, replace
printed circuit board. (h) If everything checks out OK, refer to sending
unit test.
(4) If fuel gauge does not meet specifications, refer
to Group 14, Fuel for the test procedure.
GAUGE CALIBRATION
(1) Remove the gauge.
(2) Check for ignition voltage and ground to the
gauge. (3) With the ignition key in the OFF position, re-
place gauge. Turn the ignition key to the ON posi-
tion. To test oil pressure gauge engine must be
running. When testing oil or temperature gauge the
engine should be at normal operating temperature.
Record the gauge position. (4) Remove gauge and record the resistance be-
tween the sending unit pin and the gauge ground
pin. When checking gauges, it is important to have
the same engine temperature and speed when noting
gauge position. The time between gauge reading and
measuring should be kept to a minimum. (5) The Gauge Resistance Chart (Fig. 24), is gen-
eral guidelines for checking the gauge position
against the sending unit resistance. Because of only a few specific points of gauge posi-
tion versus sending unit resistance, a good estimate
is need when the resistance falls between gradua-
tions. Even when the resistance corresponds to grad-
uations, the gauge has a tolerance of 64 ohms.
Volt gauge: The calibration dot on the volt gauge
corresponds to 13 volts between the gauge ignition
and ground pins. If voltage varies from this, estimate
proper gauge position with input voltage.
TACHOMETER REPLACEMENT
(1) Remove cluster, radio and rear window defog-
ger bezels and mask/lens assembly. (2) Remove screws attaching tachometer to cluster
housing. (3) Pull tachometer rearward to remove.
(4) For installation reverse above procedures.
TACHOMETER CIRCUIT TESTING
(1) Remove cluster, radio and rear window defog-
ger bezels and mask/lens assembly. (2) Check for battery voltage at cavity A of the in-
strument cluster black connector. (3) With the ignition in the ON position, check for
battery voltage at cavity C of the black connector
(Fig. 25).
Fig. 24 Gauge Resistance
Fig. 25 Printed Circuit Board 11-Way Connector
Ä INSTRUMENT PANEL AND GAUGES 8E - 9