check engine CHEVROLET DYNASTY 1993 Repair Manual

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 ON or OFF po-
sition, or when the radio frequency is being dis-
played, time keeping is accurately maintained. The procedure for setting the clock varies slightly
with each radio. The correct procedure is described
under the individual radio operating instructions re-
ferred to in the Owner's manual supplied with the
vehicle.
WARNING LAMPS
The AG & AJ Body instrument clusters have warn-
ing lamps or indicators with the electronic cluster for
six different systems. These include low oil pressure,
check gauges, brake system, air bag, seat belt, mal-
function indicator (check engine) lamp.
CLUSTER AND GAUGE SERVICE AND TESTING
CAUTION: Disconnect negative battery cable, in en-
gine compartment, before servicing instrument
panel. When power is required for test purposes,
reconnect battery cable for test only. Disconnect negative battery cable after test and be-
fore continuing service procedures. It is not necessary to remove instrument cluster
from vehicle for gauge replacement. Gauges must be pulled straight out, when remov-
ing or pins may be damaged.
SWITCH POD ASSEMBLY REMOVAL
(1) Disconnect negative battery cable.
(2) Pry up edge of panel vent grille, using a
straight flat edge tool to disengage clips, then re-
move grille (Fig. 4). (3) Remove two screws located under panel vent
grille. (4) Remove two screws underneath switch POD as-
sembly. (5) With tilt steering adjust steering wheel to the
lowest setting. (6) Pull switch module rearward to remove module
and disconnect all wire connections. (7) For Installation reverse above procedures.
Tighten all screws to 2 N Im (20 in. lbs.) torque.
MECHANICAL/ELECTRONIC CLUSTER REMOVAL
CLUSTER MASK AND LENS REMOVAL
(1) Remove switch pod assembly (Fig. 4).
(2) Remove tilt column lever if equipped.
(3) Remove steering column trim cover.
Fig. 4 Switch POD Assembly
Ä INSTRUMENT PANEL AND GAUGES 8E - 43

(3) When testing temperature and oil pressure
gauge, allow the engine to run until the vehicle
reaches a normal operating temperature. Turn igni-
tion 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 Resistance (Fig. 12). (c) When checking temperature and oil pressure
gauges, it is important to have the same engine
temperature and engine speed when noting gauge
position. Therefore, time between noting gauge po-
sition 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, measure the resistance between the
sending unit pin in question and the ground pin at
the cluster wire harness connectors.
Fig. 8 Fuel Gauge Pins
Fig. 9 Voltmeter Pins
Fig. 10 Temperature Gauge Pins
Fig. 11 Oil Pressure Gauge Pins
Ä INSTRUMENT PANEL AND GAUGES 8E - 45

(f) If there is a difference in readings, check
printed circuit board for contact to cluster connec-
tors. (g) If OK and contacts are not distorted, replace
printed circuit board. (h) If everything checks out OK, refer to Sending
Unit Test.
(4) The Gauge Resistance Chart (Fig. 12), is gen-
eral guidelines for checking the gauge position
against the sending unit resistance. Because of only
a few specific points of gauge position versus sending
unit resistance, a good estimate is needed when the
resistance falls between graduations. Even when the
resistance corresponds to graduations, 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 AND TURBO GAUGE REMOVAL
(1) Remove switch pod assembly.
(2) Remove steering column trim cover.
(3) Remove cluster mask and lens assembly.
(4) Remove screws attaching tachometer to cluster
housing. (5) Pull tachometer rearward to remove.
(6) Disconnect turbo gauge hose. If turbo hose can-
not be disconnected, remove cluster. (7) For installation reverse above procedures.
TACHOMETER CIRCUIT TESTING
(1) Remove cluster. (2) Check for battery voltage at cavity 8 of the in-
strument cluster red connector (Fig.6). (3) With the ignition in the ON position, check for
battery voltage at cavity 9 of the instrument cluster
red connector. (4) Check cavity 14 of the instrument cluster red
connector for continuity to ground. (5) Check for tachometer signal from the power-
train control module by connecting an AC DIGITAL
VOLTMETER to cavity 6 of the instrument cluster
black connector and ground. A reading of at least 1.0
volt should be present with the engine running (Fig.
7). (a) If voltage is within specification, go to step 7.
(b) If voltage is NOT within specification, per-
form steps 6.
(6) If there is less than 1.0 volt at cavity 6, check
for continuity between cavity 6 and pin 43 of the
powertrain control module connector. (a) If continuity is OK, between cavity 6 and pin
43 of the powertrain control module connector, re-
place the powertrain control module. (b) No continuity check the connectors for dam-
aged pins or terminal push outs or defective wire.
(7) If all tests performed test good replace the ta-
chometer drive module. (8) If the tachometer continues to be inoperative,
replace the tachometer assembly.
VOLTMETER, TEMPERATURE GAUGE, OIL PRESSURE GAUGE AND FUEL GAUGEASSEMBLYÐREMOVAL
(1) Remove pod switch assembly.
(2) Remove steering column trim cover.
(3) Remove cluster mask and lens assembly.
(4) Remove screws attaching gauge assembly to
cluster. (5) Pull rearward to remove gauge assembly.
(6) For installation reverse above procedures.
SENDING UNIT TEST
It is not necessary to remove instrument clus-
ter from vehicle for gauge replacement. When removing gauge assemblies from cluster,
gauge must be pulled straight out, not twisted, or
damage to gauge pin may result. 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.
Fig. 12 Gauge Resistance
8E - 46 INSTRUMENT PANEL AND GAUGES Ä

(3) With the ignition switch ON, an open (discon-
nected sending unit wire) causes the oil, fuel or tem-
perature gauge to read below low, empty or cold
indicators. (4) If steps 2 and 3 check OK, refer to the individ-
ual sending unit test procedures.
FUEL TANK SENDING UNIT TEST
Refer to Group 14, Fuel for test procedure.
CHECK GAUGES WARNING LAMP TESTS
The check gauges warning lamp will illuminated
when the ignition key is turned to the ON position.
The lamp will illuminate if the engine oil pressure
drops below a safe level. The check gauge lamp will
light for high engine temperature or for 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
sending unit, which is located at the front of the en-
gine (Fig. 13). If the wire at the connector checks
good pull connector loose from the switch terminal
and with a jumper wire ground connector to the en-
gine. With the ignition key turned to the ON posi-
tion check the warning lamp. If lamp still fails to
light, inspect for a burned lamp. If lamp still fails to
light, inspect for a burned out lamp or disconnected
socket in the cluster.
To test the switch disconnect the switch electrical
connector. Attach positive lead of an ohmmeter to
the switch terminal for the gray (GY) wire and the
negative lead to an engine ground. With the engine
off, there should be continuity in the system. Start
the engine. With the engine running, the ohmmeter
should show no continuity. If the above results are
not obtained, replace the switch.
COMBINATION OIL SENDING UNIT TEST
The combination oil sending unit has two func-
tions: (1) The normal closed circuit keeps the oil pressure
warning lamp on until there is oil pressure. (2) The sending unit provides a resistance that
varies with oil pressure. To test the normally closed oil lamp circuit, discon-
nect 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 (Fig. 14).
If there is oil pressure, the ohmmeter should read
an open circuit. To test the sending unit, measure the resistance
between the sending unit terminal and the metal
housing. The ohmmeter should read open. Start the
engine. The ohmmeter should read between 30 to 55 ohms,
depending on engine speed, oil temperature, and oil
viscosity. If the above results are not obtained, replace the
sending unit.
SEAT BELT WARNING SYSTEM
For testing of this system refer to Group 8U,
Chime Warning/Reminder System.
MALFUNCTION INDICATOR (CHECK ENGINE) SYSTEM
For testing this system refer to the Body Diagnos-
tic Procedures booklet.
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 or
disconnected wire at switch. The lamp also lights
when the ignition switch is turned to START. Refer
to Brake System Warning Lamp Diagnosis Chart
(Fig. 15). To test service brake warning system, raise vehicle
on a hoist and open a wheel cylinder bleeder while aFig. 13 Combination Oil Sending Unit
Fig. 14 Combination Oil Sending Unit Test
Ä INSTRUMENT PANEL AND GAUGES 8E - 47

helper depresses brake pedal and observes warning
lamp. If lamp fails to light, inspect for a burned out
lamp, disconnected socket, a broken or disconnected
wire at switch.If lamp is not burned out and wire continuity is
proven, replace brake warning switch in brake line
TEE fitting mounted on frame rail in engine com-
partment below master cylinder (Fig.16).
CAUTION: If wheel cylinder bleeder was opened
check master cylinder fluid level.
SPEEDOMETER SYSTEM
The vehicles are equipped with electronically
driven speedometer and odometer assemblies. The
unit has the same appearance as a conventional
speedometer but it eliminates the cable-driven me-
chanical system. A signal is sent from a transmis-
sion-mounted vehicle speed sensor to the
speedometer circuitry through the wiring harness.
By eliminating the speedometer cable, instrument
cluster service and removal is improved. Refer to Fig.
17 Speedometer Diagnosis Chart. When the speedometer is out of calibration. The
electronic automatic transaxle vehicle speed sensor
output must be calibrated to reflect the different combinations of equipment. The procedure is called
Pinion Factor, refer to Group 21, Transaxle for the
procedure.
Fig. 15 Brake System Warning Lamp Diagnosis
Fig. 16 Brake Warning Lamp Switch
8E - 48 INSTRUMENT PANEL AND GAUGES Ä

AP BODY INDEX
page page
Cluster and Gauge Service and Testing ....... 58
Gauges ................................ 61
General Information ....................... 58 Instrument Panel Replacement
.............. 72
Interior Lamp Replacement ................. 73
Switch and Panel Component Service ......... 67
GENERAL INFORMATION
INSTRUMENT CLUSTER
There are two conventional instrument cluster as-
semblies available. The clusters incorporates mag-
netic type gauges and an electronically driven
speedometer and odometer assembly (Fig. 1 and 2).
MAGNETIC GAUGES
All gauges on the AP Body clusters are the mag-
netic type gauges. When the ignition switch is in the
OFF position each gauge, except for the voltmeter
and tachometer will show a reading. However, the
readings are only accurate when the ignition switch
is in the ON position.
TACHOMETER DRIVE MODULE
The tachometer drive module is an electronic mod-
ule used to drive the magnetic tachometer in the
high line cluster. This module is located on top of the 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. The procedure for setting the clock varies slightly
with each radio. The correct procedure is described
under the individual radio operating instructions re-
fer to the Sound Systems Manual supplied with the
vehicle.
WARNING LAMPS AND INDICATOR LIGHTS
The instrument cluster has warning and indicators
lamps for eight different systems:
² Low oil pressure
² Brake warning
² Seat belt warning
² Malfunction indicator (check engine) lamp
² Air Bag
² High beam indicator
² Right and left turn signals.
² Anti-lock (ABS)
CLUSTER AND GAUGE SERVICE AND TESTING
CAUTION: Disconnect the negative battery cable
before servicing the instrument panel. When power
is required for test purposes, reconnect battery ca-
ble for test only. Disconnect the negative battery
cable after test and before continuing service pro-
cedures.
SENDING UNIT TEST
Check for a defective sending unit or wiring, when
a problem occurs with a cluster gauge. Do this before
disassembling the cluster. (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 fuel or temperature
gauge to read at or above maximum.
Fig. 1 Instrument Cluster With Tachometer
Fig. 2 Instrument Cluster Without Tachometer
8E - 58 INSTRUMENT PANEL AND GAUGES Ä

FUEL TANK SENDING UNIT TEST
Refer to Group 14, Fuel for test procedures.
LOW OIL PRESSURE WARNING LAMP TEST
The low oil pressure warning lamp will illuminate
when the ignition key is turned to the ON position
without engine running. The lamp also illuminates
should the engine oil pressure drop below a safe oil
pressure level. 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, located at the front of the engine (Fig. 3). If the
wire at the connector checks good, pull connector
loose from the switch and with a jumper wire ground
connector to the engine. With the ignition key turned
to the ON position check the warning lamp. If lamp
still fails to light, inspect for a burned out lamp or
disconnected socket in the cluster.
COMBINATION OIL SENDING UNIT TEST
The combination oil sending unit has two func-
tions: (1) The normal closed circuit keeps the oil pressure
warning lamp on until there is oil pressure (Fig. 4).
(2) The sending unit provides a resistance that
varies with oil pressure. To test the normally closed oil lamp circuit, discon-
nect the locking connector and measure the resis-
tance between the switch terminal and the metal
housing. The ohmmeter should read continuity. Start
the engine. If there is oil pressure, the ohmmeter should read
an open circuit. To test the sending unit, measure the resistance
between the sending unit terminal and the metal
housing. The ohmmeter should no continuity. Start
the engine. The ohmmeter should read between 30 to 55 ohms,
depending on engine speed, oil temperature and oil
viscosity. If the above results are not obtained, replace the
sending unit.
SEAT BELT WARNING SYSTEM
For testing of this system refer to Group 8M, Re-
straint Systems.
AIR BAG WARNING SYSTEM
For testing of this system refer to Group 8M, Re-
straint Systems.
MALFUNCTION INDICATOR (CHECK ENGINE) SYSTEM
For testing of this system using DRB II, refer to
the Body Powertrain Diagnostic Procedures.
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. Refer to Brake system warning Lamp Diagno-
sis (Fig. 5). To test system turn ignition key ON and apply
parking brake. If lamp fails to light, inspect for a
burned out lamp, disconnected socket, a broken or
disconnected wire at switch. The lamp also lights
when the ignition switch is turned to start. To test service brake warning system, raise vehicle
on a hoist and open a wheel cylinder bleeder while a
helper depresses brake pedal and observes warning
lamp. If lamp fails to light, inspect for a burned out
lamp, disconnected socket, a broken or disconnected
wire at switch. If lamp is not burned out and wire continuity is
proven, replace brake warning switch in brake line
Tee fitting mounted on frame rail in engine compart-
ment below master cylinder (Fig. 6).
CAUTION: If wheel cylinder bleeder was opened
check master cylinder fluid level.
Fig. 3 Combination Oil Sending Unit
Fig. 4 Combination Oil Sending Unit Test
Ä INSTRUMENT PANEL AND GAUGES 8E - 59

(5) Reconnect battery.
GAUGES
CAUTION: During the removal and installation
watch overlays are not damage.
It is not necessary to remove instrument cluster
from vehicle for gauge replacement. When removing gauge assemblies from cluster,
gauge must be pulled straight out, not twisted, or
damage to gauge pins may result.
MULTIPLE GAUGE INOPERATIVE
Volt, speedometer, tachometer and other gauges
appear to malfunction. Also check warning indicator
lamps: (1) Remove cluster
(2) Check for ignition voltage at pin E of the red
connector. If no voltage, repair as necessary (Fig. 8). (3) Check for ground continuity between pin C of
the gray connector. If no ground, repair as necessary. (4) If voltage and ground OK and pins or connec-
tors are not distorted, replace printed circuit board. (5) Install cluster.
SINGLE GAUGE INOPERATIVE (FIG. 9 AND10)
(1) Remove gauge in question. (2) With the ignition key ON, check for ignition
voltage at ignition pin of gauge. Check for ground at
ground pin of gauge. (a) If no voltage or ground, remove cluster and
check pin E red connector for ignition voltage or
pin C gray connector for ground (Fig. 8). (b) If no voltage or ground, repair as necessary.
Refer to 8W, Wiring Diagrams. (c) If there is voltage or ground, check cluster for
distorted terminals. If terminals are OK, replace
printed circuit board.
(3) When testing the temperature gauge, allow the
engine to run until the vehicle reaches a normal op-
erating temperature. Turn ignition OFF and remove
gauge from cluster.
² When checking the temperature and oil pressure
gauges, it is important to have the same engine tem-
perature and engine speed when noting gauge posi-
tion.
² The time between gauge position reading and
sending unit measuring should be kept to a mini-
mum.
² When testing oil pressure gauge, engine needs to
be running. (a) Measure and record the resistance between
sending unit pin and ground pin of the gauge in
question. Refer to Gauge Calibration.
Fig. 7 Upper Instrument Panel Components
Ä INSTRUMENT PANEL AND GAUGES 8E - 61

(f) If everything checks out OK, refer to Sending
Unit Test.
(4) With the ignition switch in the ON position,
check for battery voltage across the ignition pin and
the ground pin. (5) If fuel gauge meets specifications check fuel
tank and original fuel tank sending unit as follows: (a) Carefully remove fuel tank sending unit from
tank. (b) Refer to sending unit removal Group 14,
Fuel. (c) Connect sending unit wire and jumper wire
as described in the test procedure.
(6) If fuel gauge now checks within specifications,
original sending unit is electrically okay, check fol-
lowing as a possible cause: (a) Ground wire from sending unit to left side
cowl for continuity. (b) Sending unit deformed. Make sure sending
unit float arm moves freely and pick up tube is not
bent upwards creating an interference with bottom
of tank and inspect float. (c) Sending unit improperly installed. Install
properly. (d) Mounting flange on fuel tank for sending
unit deformed. Feel for interference fit of sending
unit to bottom of tank. It is permissible to bend
pick up tube down a little near mounting flange to
gain interference fit. (e) Fuel tank bottom deformed, causing improper
positioning of sending unit pick up tube. Replace or
repair tank and recheck sending unit.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) Resistance Chart (Fig. 11), is general guide-
lines 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 needed 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.
FUEL GAUGE REPLACEMENT
(1) Remove instrument cluster bezel.
(2) Remove mask and lens.
(3) If equipped with tachometer, remove three re-
taining screws and pull the tach straight back.
Fig. 10 Instrument Cluster Without Tachometer
Ä INSTRUMENT PANEL AND GAUGES 8E - 63

(4) Remove two retaining screws and pull fuel
gauge straight back. (5) For installation reverse above procedures.
TEMPERATURE GAUGE REPLACEMENT
(1) Remove instrument cluster bezel (Fig. 7).
(2) Remove mask and lens.
(3) Remove two retaining screws and pull temper-
ature gauge straight back. (4) For installation reverse above procedures.
VOLTMETER REPLACEMENT
(1) Remove instrument cluster bezel (Fig. 7).
(2) Remove mask and lens.
(3) Remove three speedometer retaining screws
and pull the speedometer straight back and set aside. (4) Remove two voltmeter retaining screws and
pull voltmeter straight back. (5) For installation, place voltmeter on gauge pins
and push until gauge is securely seated in cluster
and reverse above procedures.
TACHOMETER REPLACEMENT
(1) Remove instrument cluster bezel.
(2) Remove mask and lens.
(3) Remove three retaining screws and pull ta-
chometer straight back. (4) For installation, place tachometer on gauge
pins and push until gauge is securely seated in clus- ter and reverse above procedures.
TACHOMETER CIRCUIT TESTING
(1) Remove cluster.
(2) Check for battery voltage at cavity J if instru-
ment cluster gray connector. (3) With the ignition in the ON position, check for
battery voltage at cavity K of the instrument cluster
gray connector (Fig. 8). (4) Check cavity F of the instrument cluster red
connector for continuity to ground (Fig. 8). (5) Check for tachometer signal from the power-
train control module by connecting an AC DIGITAL
VOLTMETER to cavity H of the instrument cluster
gray connector and ground. A reading of at least 1.0
volts should be present with the engine running. (a) If voltage is within specification, go to step 7.
(b) If voltage is NOT within specification, per-
form steps 5 and 6.
(6) If there is less than 1.0 volts at cavity H check
for continuity between cavity H of the instrument
cluster and pin 43 of the powertrain control module
connector (Fig. 12). Also, check the connector at the
powertrain control module for damaged pins or ter-
minal push outs. (7) If voltage is less than 1.0 volts at cavity H and
there is continuity between cavity H of the instru-
Fig. 11 Gauge Resistance
8E - 64 INSTRUMENT PANEL AND GAUGES Ä