2000 DODGE NEON heating

CONDITION POSSIBLE CAUSE CORRECTION
ELECTRIC RADIATOR FAN WILL
NOT OPERATE. GAUGE READING
HIGH OR HOT1. Fan motor defective. 1. Refer to appropriate Powertrain
Diagnostic Procedures manual for
operation of the DRB scan tool.
Repair as necessary.
2. Fan relay, powertrain control
module (PCM) or engine coolant
temperature sensor defective.2. Refer to appropriate Powertrain
Diagnostic Procedures manual for
operation of the DRB scan tool.
Repair as necessary.
3. Blown fuse in power distribution
center (PDC).3. Determine reason for blown fuse
and repair as necessary.
NOISY FAN 1. Fan blade loose. 1. Replace fan blade assembly.
Refer to Cooling System Fan in this
section.
2. Fan blade striking a surrounding
object.2. Locate point of fan blade contact
and repair as necessary.
3. Air obstructions at radiator or A/C
condenser.3. Remove obstructions and/or
clean debris from radiator and/or
A/C condenser.
4. Electric fan motor defective. 4. Refer to procedure in this section.
INADEQUATE AIR CONDITIONER
PERFORMANCE (COOLING
SYSTEM SUSPECTED)1. Radiator and/or air conditioning
condenser is restricted, obstructed
or dirty.1. Remove restriction and/or clean
as necessary.
2. Electric radiator fan not operating
when A/C is on.2. Refer to appropriate Powertrain
Diagnostic Procedures manual for
operation of the DRB scan tool.
Repair as necessary.
3. Engine is overheating (heat may
be transferred from radiator to A/C
condenser). High underhood
temperature due to engine
overheating may also transfer heat
to A/C components.3. Correct overheating condition.
Refer to this section.
PLCOOLING SYSTEM 7 - 11
DIAGNOSIS AND TESTING (Continued)

OPERATION
The Automatic Shutdown (ASD) relay supplies bat-
tery voltage to the fuel injectors, electronic ignition
coil and the heating elements in the oxygen sensors.
A buss bar in the Power Distribution Center (PDC)
supplies voltage to the solenoid side and contact side
of the relay. The fuse also protects the power circuit
for the fuel pump relay and pump. The fuse is
located in the PDC. Refer to the Wiring Diagrams for
circuit information.
The PCM controls the ASD relay by switching the
ground path for the solenoid side of the relay on and
off. The PCM turns the ground path off when the
ignition switch is in the Off position. When the igni-
tion switch is in On or Start, the PCM monitors the
crankshaft and camshaft position sensor signals to
determine engine speed and ignition timing (coil
dwell). If the PCM does not receive crankshaft and
camshaft position sensor signals when the ignition
switch is in the Run position, it will de-energize the
ASD relay.
CRANKSHAFT POSITION SENSORÐPCM
INPUT
DESCRIPTION
The crankshaft position sensor mounts to the
engine block behind the generator, just above the oil
filter (Fig. 4).
The PCM uses the Crankshaft Position sensor to
calculate the following:
²Engine RPM²TDC number 1 and 4
²Ignition coil synchronization
²Injector synchronization
²Camshaft-to-crankshaft misalignment (Timing
belt skipped 1 tooth or more diagnostic trouble code).
OPERATION
The Crankshaft Position (CKP) sensor is a Hall-ef-
fect sensor. The second crankshaft counterweight has
two sets of four timing reference notches including a
60 degree signature notch (Fig. 5).
Fig. 5 Timing Reference Notches
1 ± MACHINED NOTCHES
2 ± CRANKSHAFT POSITION SENSOR
Fig. 4 Crankshaft Position Sensor
1 ± CRANKSHAFT POSITION SENSOR
2 ± OIL FILTER
3 ± GENERATOR
PLIGNITION SYSTEM 8D - 3
DESCRIPTION AND OPERATION (Continued)

(4) Discharge air conditioning system, if equipped.
Refer to Group 24, Heating and Air Conditioning for
procedure.
(5) Disconnect the following: air intake duct at
intake manifold, throttle cables, electrical connectors
from throttle body and air cleaner housing.
(6) Remove air cleaner housing assembly.
(7) Remove upper radiator hose and fan module.
Refer to Group 7, Cooling System for procedure.
(8) Remove lower radiator hose.
(9) Disconnect automatic transmission cooler lines
and plug, if equipped.
(10) Disconnect shift linkage, electrical connectors,
and clutch cable, if equipped with manual transaxle.
(11) Disconnect engine wiring harness.
(12) Disconnect positive cable from Power Distri-
bution Center (PDC) and ground wire from vehicle
body.
(13) Disconnect ground wire from the vehicle body-
to-engine at the right side strut tower.
(14) Disconnect heater hoses.
(15) Disconnect vacuum hose from brake booster.
(16) Disconnect coolant reserve/recovery hose.
(17) Remove accessory drive belts. Refer to Group
7, Cooling System for procedure.
(18) Remove power steering pump and reservoir
and set them aside.
(19) Hoist vehicle and remove right inner splash
shield.
(20) Drain engine oil.
(21) Remove front wheels.
(22) Remove axle shafts. Refer to Group 3, Differ-
ential and Driveline for procedure.
(23) Disconnect exhaust system from manifold.
(24) Disconnect the downstream oxygen sensor
connector.
(25) Remove lower engine torque strut.
(26) Remove structural collar. Refer to procedure
in this section.
(27) Lower vehicle and remove A/C compressor.
(28) Raise vehicle enough to allow engine dolly
and cradle, Special Tools 6135 and 6710 to be
installed under vehicle.
(29) Loosen engine support posts to allow move-
ment for positioning onto engine locating holes and
flange on the engine bedplate. Lower vehicle and
position cradle until the engine is resting on support
posts (Fig. 26). Tighten mounts to cradle frame. This
will keep support posts from moving when removing
or installing engine and transmission.
(30) Install safety straps around the engine to cra-
dle (Fig. 26). Tighten straps and lock them into posi-
tion.
WARNING: Safety straps MUST be used.(31) Raise vehicle enough to see if straps are tight
enough to hold cradle assembly to engine.
(32) Lower vehicle so weight of the engine and
transmission ONLY is on the cradle assembly.
(33) Remove the upper engine torque strut.
(34) Remove right and left engine and transaxle
mount through bolts (Fig. 24) and (Fig. 25).
(35) Raise vehicle slowly until body is approxi-
mately 15 cm (6 in.) above normal engine mounting
locations.
(36) Remove generator, lower bracket, and upper
mounting bolt.
(37) Continue raising vehicle slowly until engine/
transaxle assembly clears engine compartment. It
may be necessary to move the engine/transmission
assembly with the cradle to allow for removal around
body flanges.
INSTALLATION
(1) Position engine and transmission assembly
under vehicle and slowly lower the vehicle over the
engine/transaxle assembly until vehicle is within 15
cm (6 in.) of engine mounting locations.
(2) Install generator, lower bracket, and adjusting
bolt.
(3) Continue lowering vehicle until engine/tran-
saxle aligns to mounting locations. Install mounting
bolts at the right and left engine/transaxle mounts
(Fig. 24) and (Fig. 25). Tighten bolts to 118 N´m (87
ft. lbs.).
(4) Install upper engine torque strut. Refer to pro-
cedure in this section.
(5) Remove safety straps from engine/transaxle
assembly. Slowly raise vehicle enough to remove the
engine dolly and cradle.
(6) Install axle shafts. Refer to Group 3, Differen-
tial and Driveline for procedure.
(7) Install structural collar. Refer to procedure in
this section tightening sequence.
Fig. 24 Right Mount Through Bolt
1 ± BOLT
2 ± RIGHT ENGINE MOUNT
3 ± ENGINE MOUNT BRACKET
9 - 26 2.0L SOHC ENGINEPL
REMOVAL AND INSTALLATION (Continued)

²All inputs monitored for proper voltage range.
²All monitored components (refer to the Emission
section for On-Board Diagnostics).
The PCM compares the upstream and downstream
heated oxygen sensor inputs to measure catalytic
convertor efficiency. If the catalyst efficiency drops
below the minimum acceptable percentage, the PCM
stores a diagnostic trouble code in memory.
During certain idle conditions, the PCM may enter
a variable idle speed strategy. During variable idle
speed strategy the PCM adjusts engine speed based
on the following inputs.
²A/C sense
²Battery voltage
²Battery temperature
²Engine coolant temperature
²Engine run time
²Power steering pressure switch
²Vehicle mileage
ACCELERATION MODE
This is a CLOSED LOOP mode. The PCM recog-
nizes an abrupt increase in Throttle Position sensor
output voltage or MAP sensor output voltage as a
demand for increased engine output and vehicle
acceleration. The PCM increases injector pulse width
in response to increased fuel demand.
DECELERATION MODE
This is a CLOSED LOOP mode. During decelera-
tion the following inputs are received by the PCM:
²A/C pressure transducer
²A/C sense
²Battery voltage
²Intake air temperature
²Engine coolant temperature
²Crankshaft position (engine speed)
²Exhaust gas oxygen content (upstream heated
oxygen sensor)
²Knock sensor
²Manifold absolute pressure
²Power steering pressure switch
²Throttle position
²IAC motor control changes in response to MAP
sensor feedback.
The PCM may receive a closed throttle input from
the Throttle Position Sensor (TPS) when it senses an
abrupt decrease in manifold pressure. This indicates
a hard deceleration. In response, the PCM may
momentarily turn off the injectors. This helps
improve fuel economy, emissions and engine braking.
If decel fuel shutoff is detected, downstream oxy-
gen sensor diagnostics is performed.WIDE-OPEN-THROTTLE MODE
This is an OPEN LOOP mode. During wide-open-
throttle operation, the following inputs are received
by the PCM:
²Intake air temperature
²Engine coolant temperature
²Engine speed
²Knock sensor
²Manifold absolute pressure
²Throttle position
When the PCM senses a wide-open-throttle condi-
tion through the Throttle Position Sensor (TPS) it de-
energizes the A/C compressor clutch relay. This
disables the air conditioning system.
The PCM does not monitor the heated oxygen sen-
sor inputs during wide-open-throttle operation except
for downstream heated oxygen sensor and both
shorted diagnostics. The PCM adjusts injector pulse
width to supply a predetermined amount of addi-
tional fuel.
IGNITION SWITCH OFF MODE
When the operator turns the ignition switch to the
OFF position, the following occurs:
²All outputs are turned off, unless 02 Heater
Monitor test is being run. Refer to the Emission sec-
tion for On-Board Diagnostics.
²No inputs are monitored except for the heated
oxygen sensors. The PCM monitors the heating ele-
ments in the oxygen sensors and then shuts down.
SYSTEM DIAGNOSIS
OPERATION
The PCM can test many of its own input and out-
put circuits. If the PCM senses a fault in a major
system, the PCM stores a Diagnostic Trouble Code
(DTC) in memory.
For DTC information see On-Board Diagnostics.
POWER DISTRIBUTION CENTER
The Power Distribution Center (PDC) is located
next to the battery (Fig. 1). The PDC contains the
starter relay, radiator fan relay, A/C compressor
clutch relay, auto shutdown relay, fuel pump relay
and several fuses.
POWERTRAIN CONTROL MODULE
The Powertrain Control Module (PCM) is a digital
computer containing a microprocessor (Fig. 2). The
PCM receives input signals from various switches
and sensors that are referred to as PCM Inputs.
Based on these inputs, the PCM adjusts various
engine and vehicle operations through devices that
are referred to as PCM Outputs.
PCM Inputs:
14 - 24 FUEL SYSTEMPL
DESCRIPTION AND OPERATION (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)

As the engine enters one of these cells the PCM
looks at the amount of short term correction being
used. Because the goal is to keep short term at 0 (O2
Sensor switching at 0.5 volt), long term will update
in the same direction as short term correction was
moving to bring the short term back to 0. Once short
term is back at 0, this long term correction factor is
stored in memory.
The values stored in long term adaptive memory
are used for all operating conditions, including open
loop. However, the updating of the long term memoryoccurs after the engine has exceeded approximately
17É F, with fuel control in closed loop and two min-
utes of engine run time. This is done to prevent any
transitional temperature or start-up compensations
from corrupting long term fuel correction.
Long term adaptive memory can change the pulse-
width by as much as 25%, which means it can correct
for all of short term. It is possible to have a problem
that would drive long term to 25% and short term to
another 25% for a total change of 50% away from
base pulse-width calculation.
TYPICAL ADAPTIVE MEMORY FUEL CELLS
Open
ThrottleOpen
ThrottleOpen
ThrottleOpen
ThrottleOpen
ThrottleOpen
Throttle Idle Decel
Vacuum 20 17 13 9 5 0
Above 1,984
rpm1 3 5 7 9 11 13 Drive 15
Below 1,984
rpm02 4 6 8 1012
Neutral14
MAP volt =0 1.4 2.0 2.6 3.3 3.9
Fuel Correction Diagnostics
There are two fuel correction diagnostic routines:
²Fuel System Rich
²Fuel System Lean
A DTC is set and the MIL is illuminated if the
PCM detects either of these conditions.
PROGRAMMABLE COMMUNICATIONS
INTERFACE (PCI) BUS
OPERATION
Various modules exchange information through a
communications port called the PCI Bus. The Power-
train Control Module (PCM) transmits the Malfunc-
tion Indicator Lamp (Check Engine) On/Off signal
and engine RPM on the PCI Bus. The PCM receives
the Air Conditioning select input, transaxle gear
position inputs over the PCI Bus. The PCM also
receives the air conditioning evaporator temperature
signal from the PCI Bus.
The following components access or send informa-
tion on the PCI Bus.
²Instrument Panel
²Body Control Module
²Air Bag System Diagnostic Module
²Full ATC Display Head
²ABS Module
²Transmission Control Module
²Powertrain Control Module
²Overhead Travel Module
AIR CONDITIONING PRESSURE
TRANSDUCERÐPCM INPUT
OPERATION
The Powertrain Control Module (PCM) monitors
the A/C compressor discharge (high side) pressure
through the air conditioning pressure transducer.
The transducer supplies an input to the PCM. The
PCM engages the A/C compressor clutch if pressure
is sufficient for A/C system operation.
AUTOMATIC SHUTDOWN (ASD) SENSEÐPCM
INPUT
OPERATION
The ASD sense circuit informs the PCM when the
ASD relay energizes. A 12 volt signal at this input
indicates to the PCM that the ASD has been acti-
vated. This input is used only to sense that the ASD
relay is energized.
When energized, the ASD relay supplies battery
voltage to the fuel injectors, ignition coils and the
heating element in each oxygen sensor. If the PCM
does not receive 12 volts from this input after
grounding the ASD relay, it sets a Diagnostic Trouble
Code (DTC).
PLFUEL SYSTEM 14 - 27
DESCRIPTION AND OPERATION (Continued)

HEATED OXYGEN SENSOR (O2 SENSOR)Ð
PCM INPUT
DESCRIPTION
The upstream oxygen sensor threads into the out-
let flange of the exhaust manifold (Fig. 11).
The downstream heated oxygen sensor threads into
the system depending on emission package (Fig. 12).
Federal package the O2s is mounted after the cata-
lytic convertor, LEV package the O2s is mounted mid
catalytic convertor, ULEV package is mounted
between the catalytic convertor (Fig. 13).
OPERATION
The O2 sensors produce voltages from 0 to 1 volt,
depending upon the oxygen content of the exhaust
gas in the exhaust manifold (Fig. 14). When a large
amount of oxygen is present (caused by a lean air/
fuel mixture), the sensors produce a voltage below
450 mv. When there is a lesser amount present (rich
air/fuel mixture) it produces a voltage above 450 mv.
By monitoring the oxygen content and converting it
to electrical voltage, the sensors act as a rich- lean
switch.
The oxygen sensors are equipped with a heating
element that keeps the sensors at proper operating
temperature during all operating modes. Maintaining
correct sensor temperature at all times allows the
system to enter into closed loop operation sooner.
Also, it allows the system to remain in closed loop
operation during periods of extended idle.
In Closed Loop operation the PCM monitors the O2
sensor input (along with other inputs) and adjusts
the injector pulse width accordingly. During Open
Loop operation the PCM ignores the O2 sensor input.
The PCM adjusts injector pulse width based on pre-
programmed (fixed) values and inputs from other
sensors.
The Automatic Shutdown (ASD) relay supplies bat-
tery voltage to both the upstream and downstream
heated oxygen sensors. The oxygen sensors are
equipped with a heating element. The heating ele-
ments reduce the time required for the sensors to
reach operating temperature.
UPSTREAM OXYGEN SENSOR 1/1
The input from the upstream heated oxygen sensor
tells the PCM the oxygen content of the exhaust gas.
Based on this input, the PCM fine tunes the air-fuel
ratio by adjusting injector pulse width.
The sensor input switches from 0 to 1 volt, depend-
ing upon the oxygen content of the exhaust gas in
the exhaust manifold. When a large amount of oxy-
gen is present (caused by a lean air-fuel mixture), the
sensor produces voltage as low as 0.1 volt. When
there is a lesser amount of oxygen present (rich air-
fuel mixture) the sensor produces a voltage as high
as 1.0 volt. By monitoring the oxygen content and
converting it to electrical voltage, the sensor acts as
a rich-lean switch.
The heating element in the sensor provides heat to
the sensor ceramic element. Heating the sensor
allows the system to enter into closed loop operation
sooner. Also, it allows the system to remain in closed
loop operation during periods of extended idle.
In Closed Loop, the PCM adjusts injector pulse
width based on the upstream heated oxygen sensor
input along with other inputs. In Open Loop, the
PCM adjusts injector pulse width based on prepro-
Fig. 11 Upstream Heated Oxygen Sensor 1/1
1 ± OXYGEN SENSORS
2 ± EXHAUST MANIFOLD
Fig. 12 Downstream Heated Oxygen Sensor 1/2
14 - 32 FUEL SYSTEMPL
DESCRIPTION AND OPERATION (Continued)

Like all Hall-effect sensors, the electronics of the
sensor needs a power source. This power source is
provided by the PCM. It is the same 8 volt power
supply that is used by the CKP and CMP sensors.
The vehicle speed sensor generates 8 pulses per
sensor revolution. This signal, in conjunction with a
closed throttle signal from the throttle position sen-
sor, indicates a closed throttle deceleration to the
PCM. Under deceleration conditions, the PCM
adjusts the Idle Air Control (IAC) motor to maintain
a desired MAP value.
When the vehicle is stopped at idle, a closed throt-
tle signal is received by the PCM (but a speed sensor
signal is not received). Under idle conditions, the
PCM adjusts the IAC motor to maintain a desired
engine speed.
AIR CONDITIONING CLUTCH RELAYÐPCM
OUTPUT
DESCRIPTION
The air conditioning clutch relay is located in the
PDC. The inside top of the PDC cover has a label
showing relay and fuse location.
OPERATION
The PCM controls the air conditioning clutch relay
ground circuit. The A/C clutch relay coil side contains
a 10 amp fuse between the buss bar in the Power
Distribution Center (PDC) and the relay. The power
side of this relay is fused with a 40 amp fuse. When
the PCM receives an air conditioning input, it
grounds the A/C compressor clutch relay and the
radiator fan relay.
When the PCM senses low idle speeds or wide open
throttle through the throttle position sensor, it
removes the ground for the A/C compressor clutch
relay. When the relay de-energizes, the contacts open
preventing air conditioning clutch engagement. Also,
if the PCM senses a part throttle launch condition, it
disables the A/C compressor clutch for several sec-
onds.
AUTOMATIC SHUTDOWN RELAYÐPCM
OUTPUT
DESCRIPTION
The ASD relay is located in the PDC. The inside
top of the PDC cover has a label showing relay and
fuse location.
OPERATION
The automatic shutdown (ASD) relay supplies bat-
tery voltage to the fuel injectors, electronic ignition
coil and the heating elements in the oxygen sensors
generator field and PCM sense circuit.A buss bar in the power distribution center (PDC)
supplies voltage to the solenoid side and contact side
of the relay. The ASD relay power circuit contains a
fuse between the buss bar in the PDC and the relay.
The fuse also protects the power circuit for the fuel
pump relay and pump. The fuse is located in the
PDC. Refer to the Wiring Diagrams for circuit infor-
mation.
The PCM controls the relay by switching the
ground path for the solenoid side of the relay on and
off. The PCM turns the ground path off when the
ignition switch is in the Off position unless the 02
Heater Monitor test is being run. When the ignition
switch is in the On or Crank position, the PCM mon-
itors the crankshaft position sensor and camshaft
position sensor signals to determine engine speed
and ignition timing (coil dwell). If the PCM does not
receive the crankshaft position sensor and camshaft
position sensor signals when the ignition switch is in
the Run position, it will de-energize the ASD relay.
CHARGING SYSTEM INDICATOR LAMPÐPCM
OUTPUT
OPERATION
The PCM turns the instrument panel Charging
System Lamp on. Refer to the Charging system sec-
tion information.
FUEL PUMP RELAYÐPCM OUTPUT
DESCRIPTION
The fuel pump relay is located in the PDC. The
inside top of the PDC cover has a label showing relay
and fuse location.
OPERATION
The fuel pump relay supplies battery voltage to the
fuel pump. A buss bar in the Power Distribution Cen-
ter (PDC) supplies voltage to the solenoid side and
contact side of the relay. The fuel pump relay power
circuit contains a fuse between the buss bar in the
PDC and the relay. The fuse also protects the power
circuit for the Automatic Shutdown (ASD) relay. The
fuse is located in the PDC. Refer to the Wiring Dia-
grams for circuit information.
The PCM controls the fuel pump relay by switch-
ing the ground path for the solenoid side of the relay
on and off. The PCM turns the ground path off when
the ignition switch is in the Off position. When the
ignition switch is in the On position, the PCM ener-
gizes the fuel pump. If the crankshaft position sensor
does not detect engine rotation, the PCM de-ener-
gizes the relay after approximately one second.
14 - 38 FUEL SYSTEMPL
DESCRIPTION AND OPERATION (Continued)