
DESCRIPTION AND OPERATION
HEADLAMP SWITCH
The headlamp switch is part of the Multi-Function
Switch. Refer to Group 8J, Turn Signal and Flasher
for the Multi-Function Switch Test, Removal and
Installation procedures.
INSTRUMENT CLUSTER
There are two conventional instrument cluster
assemblies available. The clusters electronically drive
the speedometer, odometer, gauges, and tachometer
(if equipped). Refer to (Fig. 2) and (Fig. 3).
The instrument cluster controls the courtesy
lamps, it receives and sends messages to other mod-
ules via the PCI bus circuit, it controls all the instru-
ment illumination and the chime is also an integral
part of the cluster. The front turn signals are wired
through the cluster and then go to the front lamps.
The reason being that the DRL module is built into
the cluster (if equipped).
All gauges in the electronic clusters are the analog
type gauges. When the ignition switch is moved to
the OFF position, the cluster drives each gauge to its
lowest position. The individual gauges are not servi-
cable and require complete replacement of the cluster
if one or more gauges are inoperable.
One button is used to switch the display from trip
to total mileage. Holding the button when the display
is in the trip mode will reset the trip mileage. This
button is also used to put the cluster in self-diagnos-
tic mode. Refer to Service Procedures, Cluster Self-
Diagnostics in this section. Most of the indicators will
come on briefly for a bulb heck when the ignition is
turned from OFF to ON. All of the LED's are replace-
able.
In the event that the instrument cluster looses
communication with all other modules on the PCI
bus, the cluster will display ªnobusº in the VF dis-
play. The VF display also displays ªDoorº, ªCruiseº,
ªTracº, and odometer trip or total.
If the cluster does not detect voltage on the cour-
tesy lamp circuit, the message ªFUSEº will alternate
with the odometer/trip odometer for 30 seconds after
the ignition is turned on and for 15 seconds after the
vehicle is first moved. The lack of voltage can be due
to the M1 Fused B(+) (IOD) fuse being open, a bad or
missing courtesy lamp bulb, or a circuit problem.
WARNING AND INDICATOR LAMPS
The instrument cluster has warning lamps and
indicators for the following systems:
²Airbag
²Anti-lock Brakes (ABS) if equipped
²Brake warning
²Charging System²Front fog lamps (if equipped)
²High beam indicator
²Low fuel (premium cluster only)
²Low oil pressure
²Malfunction indicator (service engine soon) lamp
²Right and left turn signals
²Seat belt warning
²Security system
²Trac-Off (ABS equipped vehicles only)
The instrument cluster has a Vacuum Fluorescent
(VF) display for the following systems:
²Cruise
²Door (ajar)
²Odometer
²Set (cruise)
²Trac
²Trip
DIAGNOSIS AND TESTING
AIRBAG WARNING SYSTEM
For testing of this system refer to Group 8M, Pas-
sive Restraint Systems.
BRAKE SYSTEM WARNING LAMP TEST
The brake warning lamp illuminates when the
parking brake is applied with ignition switch turned
to the ON position. The same lamp will also illumi-
nate if one of the two service brake systems fail the
when brake pedal is applied.
To test the system:
²As the ignition switch is turned to the start posi-
tion the lamp should light.
²Turn ignition switch to the ON position and
apply the parking brake. The lamp should light.
If lamp fails to light inspect for:
²A burned out lamp
²Loose, corroded or damaged socket
²A damaged circuit board
²A broken or disconnected wire at the switch
²Defective switch
To test the service brake warning system, refer to
Group 5, Brakes, Hydraulic System Control Valves.
INSTRUMENT CLUSTER LAMPS
Every time the vehicle is switched to the START/
RUN position, the cluster goes through a BULB
CHECK. This tests most of the indicator lamps and
Vacuum Fluorescent (VF) displays. If only one lamp
is out, remove the instrument cluster and replace the
defective bulb or Light Emitting Diode (LED). If
some or all of the lamps fail to light, refer to the
proper Body Diagnostics Procedures Manual.
8E - 2 INSTRUMENT PANEL SYSTEMSPL

To diagnose the cluster lamps first place the clus-
ter in self-diagnostic mode. With the ignition switch
in the off position, press the trip odometer reset but-
ton down. Simultaneously turn the ignition key to
the ON position and release the trip reset button. All
the indicator lamps and VF displays should illumi-
nate except for the fog lamp, turn signal, and high
beam select indicators. Refer to (Fig. 2), (Fig. 3), and
the Cluster Identification table.
1 ± FOG LAMP
2 ± BRAKE**
3 ± TRAC OFF**
4 ± ABS**
5 ± SPEEDOMETER
6 ± LEFT/RIGHT TURN SIGNAL
7 ± HIGH BEAM
8 ± TACHOMETER
9 ± OIL PRESSURE**
10 ± SEAT BELT**
11 ± BATTERY**
12 ± AIR BAG**
13 ± SECURITY*
14 ± FUEL FILLER DOOR LOCATOR
15 ± FUEL GAUGE
16 ± LOW FUEL*
17 ± MALFUNCTION INDICATOR LAMP (MIL)**
18 ± TRIP RESET BUTTON
19 ± TRAC**
20 ± ODOMETER**
21 ± DOOR (AJAR)**
22 ± SET CRUISE*
23 ± TRIP**
24 ± CRUISE*
25 ± TEMPERATURE GAUGE
*ILLUMINATE DURING SELF-DIAGNOSTICS
**ILLUMINATE DURING BULB CHECK AND SELF-DIAGNOSTICS
LOW OIL PRESSURE WARNING LAMP TEST
The low oil pressure warning lamp will illuminate
when the ignition switch is turned to the ON position
without engine running. The lamp also illuminates if
the engine oil pressure drops below a safe oil pres-
sure level.To test the system, turn the ignition switch to the
ON position. If the lamp fails to light, inspect for a
broken or disconnected wire at the oil pressure
switch, located at the front of the engine (Fig. 4). If
the wire at the connector checks good, pull the con-
nector loose from the switch and with a jumper wire,
ground the connector to the engine. With the ignition
switch turned to the ON position, check the warning
lamp. If the lamp still fails to light, inspect for a
burned out lamp or disconnected socket in the clus-
ter.
Fig. 2 Base Instrument Cluster Without Tachometer
Fig. 3 Premium Instrument Cluster With Tachometer
1 ± FOG LAMP
2 ± BRAKE**
3 ± TRAC OFF**
4 ± ABS**
5 ± SPEEDOMETER
6 ± LEFT/RIGHT TURN SIGNAL
7 ± HIGH BEAM
8 ± TACHOMETER
9 ± OIL PRESSURE**
10 ± SEAT BELT**
11 ± BATTERY**
12 ± AIR BAG**
13 ± SECURITY*
14 ± FUEL FILLER DOOR LOCATOR
15 ± FUEL GAUGE
16 ± LOW FUEL*
17 ± MALFUNCTION INDICATOR LAMP (MIL)**
18 ± TRIP RESET BUTTON
19 ± TRAC**
20 ± ODOMETER**
21 ± DOOR (AJAR)**
22 ± SET CRUISE*
23 ± TRIP**
24 ± CRUISE*
25 ± TEMPERATURE GAUGE
*ILLUMINATE DURING SELF-DIAGNOSTICS
**ILLUMINATE DURING BULB CHECK AND SELF-DIAGNOSTICS
PLINSTRUMENT PANEL SYSTEMS 8E - 3
DIAGNOSIS AND TESTING (Continued)

MULTIPLE/INDIVIDUAL GAUGES INOPERATIVE
Test speedometer, tachometer and other gauges for
malfunction:
(1) Remove the cluster. Refer to Cluster Removal
and Installation.
(2) Check for ignition voltage at Pin 15 of the clus-
ter wire harness connector (Fig. 5). Check for battery
voltage at Pin 21 of the connector. If no voltage,
repair as necessary.
(3) Check Pin 10 of the connector for continuity to
ground. If no ground, repair as necessary.
(4) If the voltage and ground are OK, and the pins
or the connectors are not distorted, replace the
instrument cluster.
(5) Install cluster. Refer to Instrument Cluster
Removal and Installation in this section.
SERVICE PROCEDURES
INSTRUMENT CLUSTER SELF-DIAGNOSTICS
To put the cluster in self-diagnostics mode press
the trip reset button down and then turn the ignition
to the RUN position simultaneously, then release the
button. The gauges will increment to selected stoops
and all indicators will light with the exception of the
turn signals, high beam, and fog lamp indicators.
The oil lamp will come on when the ignition is
turned ON and the engine is OFF.
REMOVAL AND INSTALLATION
ACCESSORY SWITCH/POWER OUTLET BEZEL
REMOVAL
(1) Disconnect and isolate the battery negative
cable (Fig. 6).
(2) Remove the instrument panel center bezel.
Refer to Instrument Panel Center Bezel Removal and
Installation in this section.
(3) Remove four screws retaining accessory switch/
power outlet bezel (Fig. 7).(4) Disconnect the harness connectors to the fol-
lowing:
²Rear Window Defogger Switch (if equipped)
²Traction Control Switch (if equipped)
²Cigar Lighter/Power Outlet
Fig. 5 Cluster Wire Harness Connector
INSTRUMENT CLUSTER CONNECTOR PIN
CALL-OUT
PIN DESCRIPTION PIN DESCRIPTION
1 REAR FOG
LAMP FEED14 PARK LAMP
SWITCH
OUTPUT
2 PCI BUS 15 FUSED IGNITION
SWITCH
OUTPUT
(RUN-START)
3 COURTESY
LAMPS DRIVER16 DAYTIME
RUNNING
LAMPS
4 FOG LAMP
SWITCH
OUTPUT17 DAYTIME
RUNNING
LAMPS
5 VTSS
INDICATOR
DRIVER18 LEFT TURN
SIGNAL
6 PANEL LAMPS
DIMMER
SIGNAL19 RIGHT TURN
SIGNAL
7 FUEL LEVEL
SENSOR
SIGNAL20 DIMMER
SWITCH LOW
BEAM OUTPUT
8 NOT USED 21 FUSED B+
9 NOT USED 22 RED BRAKE
WARNING
INDICATOR
DRIVER
10 GROUND 23 KEY-IN IGNITION
SWITCH SENSE
11 NOT USED 24 DRIVER DOOR
AJAR SWITCH
SENSE
12 PANEL LAMPS
DRIVER25 SEAT BELT
SWITCH SENSE
13 KEYLESS
ENTRY SIGNAL26 DIMMER
SWITCH HIGH
BEAM OUTPUT
Fig. 4 Oil Pressure Switch
8E - 4 INSTRUMENT PANEL SYSTEMSPL
DIAGNOSIS AND TESTING (Continued)

²Coolant temperature
²Engine speed (crankshaft position sensor)
²Engine run time
²Manifold absolute pressure
²Power steering pressure switch
²Throttle position
²Transmission gear selection (park/neutral
switch)
²Vehicle distance (speed)
The Auto Shutdown (ASD) and fuel pump relays
are mounted externally, but turned on and off by the
PCM.
The crankshaft position sensor signal is sent to the
PCM. If the PCM does not receive the signal within
approximately one second of engine cranking, it deac-
tivates the ASD relay and fuel pump relay. When
these relays deactivate, power is shut off from the
fuel injectors, ignition coils, heating element in the
oxygen sensors and the fuel pump.
The PCM contains a voltage converter that
changes battery voltage to a regulated 8 volts direct
current to power the camshaft position sensor, crank-
shaft position sensor and vehicle speed sensor. The
PCM also provides a 5 volt direct current supply for
the manifold absolute pressure sensor and throttle
position sensor.
PCM GROUND
OPERATION
Ground is provided through multiple pins of the
PCM connector. Depending on the vehicle there may
be as many as three different ground pins. There are
power grounds and sensor grounds.
The power grounds are used to control the ground
side of any relay, solenoid, ignition coil or injector.
The signal ground is used for any input that uses
sensor return for ground, and the ground side of any
internal processing component.
The SBEC III case is shielded to prevent RFI and
EMI. The PCM case is grounded and must be firmly
attached to a good, clean body ground.
Internally all grounds are connected together, how-
ever there is noise suppression on the sensor ground.
For EMI and RFI protection the case is also
grounded separately from the ground pins.
5 VOLT SUPPLYÐPCM OUTPUT
OPERATION
The PCM supplies 5 volts to the following sensors:
²A/C pressure transducer
²Engine coolant temperature sensor
²Manifold absolute pressure sensor
²Throttle position sensor
²Linear EGR solenoid
8-VOLT SUPPLYÐPCM OUTPUT
OPERATION
The PCM supplies 8 volts to the crankshaft posi-
tion sensor, camshaft position sensor.
FUEL CORRECTION or ADAPTIVE MEMORIES
DESCRIPTION
In Open Loop, the PCM changes pulse width with-
out feedback from the O2 Sensors. Once the engine
warms up to approximately 30 to 35É F, the PCM
goes into closed loopShort Term Correctionand
utilitzes feedback from the O2 Sensors. Closed loop
Long Term Adaptive Memoryis maintained above
170É to 190É F unless the PCM senses wide open
throttle. At that time the PCM returns to Open Loop
operation.
OPERATION
Short Term
The first fuel correction program that begins func-
tioning is the short term fuel correction. This system
corrects fuel delivery in direct proportion to the read-
ings from the Upstream O2 Sensor.
The PCM monitors the air/fuel ratio by using the
input voltage from the O2 Sensor. When the voltage
reaches its preset high or low limit, the PCM begins
to add or remove fuel until the sensor reaches its
switch point. The short term corrections then begin.
The PCM makes a series of quick changes in the
injector pulse-width until the O2 Sensor reaches its
opposite preset limit or switch point. The process
then repeats itself in the opposite direction.
Short term fuel correction will keep increasing or
decreasing injector pulse-width based upon the
upstream O2 Sensor input. The maximum range of
authority for short term memory is 25% (+/-) of base
pulse-width.
Long Term
The second fuel correction program is the long
term adaptive memory. In order to maintain correct
emission throughout all operating ranges of the
engine, a cell structure based on engine rpm and load
(MAP) is used.
There are up to 16 cells. Two cells are used only
during idle, based upon TPS and Park/Neutral
switch inputs. There may be two other cells used for
deceleration, based on TPS, engine rpm, and vehicle
speed. The other twelve cells represent a manifold
pressure and an rpm range. Six of the cells are high
rpm and the other six are low rpm. Each of these
cells is a specific MAP voltage range.
14 - 26 FUEL SYSTEMPL
DESCRIPTION AND OPERATION (Continued)

GENERAL INFORMATION
A/C APPLICATION TABLE
Item Description Notes
Vehicle PL Neon
System expansion valve
Total Refrigerant
CapacityR134a 765 grams / 27 oz / 1.69 lbs
Total Oil Capacity ND-8 PAG oil 180 ml / 6.10 oz
Compressor Nippondenso 10S17
Freeze-up Control Fin sensor-3 wire input to PCM, evaporator mounted, cycles
clutch off below 34É F, cycles back on
above 45É F
Low psi Control opens < 14 psi, resets > 38 psi expansion valve mounted
High psi Control opens > 470 psi, resets < 370 - 330 psi compressor mounted switch
Control head manual type
Mode Door cable
Blend Air Door cable
Fresh/Recirc door vacuum actuator
Blower Motor control head switched resistor block
Cooling Fan variable speed PCM controlled ISO solid state fan relay
Clutch
Control relay PCM
Draw 2.5 amps @ 12V60.5V @ 70É F
Gap 0.014º - 0.0269
DRB IIIT
Reads TPS, RPM, A/C switch test, fin sensor
A/C & fan relays
Actuators fan & clutch relays
HEATER AND AIR CONDITIONING CONTROL
Both the heater-only and heater-A/C systems use a
combination of, electrical, cable, and vacuum con-
trols. These controls provide the vehicle operator
with a number of setting options to help control the
climate and comfort within the vehicle. Refer to the
owner's manual in the vehicle glove box for more
information on the features, use, and suggested oper-
ation of these controls.
The heater-only or heater-A/C control panel is located
to the right of the instrument cluster on the instrument
panel. The control panel contains rotary-type knobs.
There is a blower motor speed switch, mode control
switch, temperature control, and airflow control.
The heater-only or heater-A/C control panel cannot
be repaired. If faulty or damaged, the entire unit
must be replaced. The control knobs and the illumi-
nation lamps are available for service replacement.
HEATER AND AIR CONDITIONING
All vehicles are equipped with a common heater-
A/C housing assembly (Fig. 1). The system combines
air conditioning, heating, and ventilating capabilities
in a single unit housing mounted under the instru-
ment panel. On heater-only systems, the evaporator
coil is omitted from the housing and replaced with an
air restrictor plate.
Outside air enters the vehicle through the cowl top
opening at the base of the windshield, and passes
through a plenum chamber to the heater-A/C system
blower housing. Air flow velocity can then be
adjusted with the blower motor speed selector switch
on the heater-A/C control panel. The air intake open-
ings must be kept free of snow, ice, leaves, and other
obstructions for the heater-A/C system to receive a
sufficient volume of outside air.
24 - 2 HEATING AND AIR CONDITIONINGPL