2000 DODGE NEON pressure

Pending ConditionsÐ
²Misfire DTC
²Front Oxygen Sensor Response
²Front Oxygen Sensor Heater Monitor
²Front Oxygen Sensor Electrical
²Rear Oxygen Sensor Rationality (middle check)
²Rear Oxygen Sensor Heater Monitor
²Rear Oxygen Sensor Electrical
²Fuel System Monitor
²All TPS faults
²All MAP faults
²All ECT sensor faults
²Purge flow solenoid functionality
²Purge flow solenoid electrical
²All PCM self test faults
²All CMP and CKP sensor faults
²All injector and ignition electrical faults
²Idle Air Control (IAC) motor functionality
²Vehicle Speed Sensor
²Brake switch
²Intake air temperature
ConflictÐThe catalyst monitor does not run if
any of the following are conditions are present:
²EGR Monitor in progress
²Fuel system rich intrusive test in progress
²EVAP Monitor in progress
²Time since start is less than 60 seconds
²Low fuel level
²Low ambient air temperature
SuspendÐThe Task Manager does not mature a
catalyst fault if any of the following are present:
²Oxygen Sensor Monitor, Priority 1
²Upstream Oxygen Sensor Heater, Priority 1
²EGR Monitor, Priority 1
²EVAP Monitor, Priority 1
²Fuel System Monitor, Priority 2
²Misfire Monitor, Priority 2
NON-MONITORED CIRCUITS
OPERATION
The PCM does not monitor all circuits, systems
and conditions that could have malfunctions causing
driveability problems. However, problems with these
systems may cause the PCM to store diagnostic trou-
ble codes for other systems or components. For exam-
ple, a fuel pressure problem will not register a fault
directly, but could cause a rich/lean condition or mis-
fire. This could cause the PCM to store an oxygen
sensor or misfire diagnostic trouble code.
The major non-monitored circuits are listed below
along with examples of failures modes that do not
directly cause the PCM to set a DTC, but for a sys-
tem that is monitored.FUEL PRESSURE
The fuel pressure regulator controls fuel system
pressure. The PCM cannot detect a clogged fuel
pump inlet filter, clogged in-line fuel filter, or a
pinched fuel supply or return line. However, these
could result in a rich or lean condition causing the
PCM to store an oxygen sensor or fuel system diag-
nostic trouble code.
SECONDARY IGNITION CIRCUIT
The PCM cannot detect an inoperative ignition coil,
fouled or worn spark plugs, ignition cross firing, or
open spark plug cables.
CYLINDER COMPRESSION
The PCM cannot detect uneven, low, or high engine
cylinder compression.
EXHAUST SYSTEM
The PCM cannot detect a plugged, restricted or
leaking exhaust system. It may set a EGR or Fuel
system fault or O2S.
FUEL INJECTOR MECHANICAL MALFUNCTIONS
The PCM cannot determine if a fuel injector is
clogged, the needle is sticking or if the wrong injector
is installed. However, these could result in a rich or
lean condition causing the PCM to store a diagnostic
trouble code for either misfire, an oxygen sensor, or
the fuel system.
EXCESSIVE OIL CONSUMPTION
Although the PCM monitors engine exhaust oxygen
content when the system is in closed loop, it cannot
determine excessive oil consumption.
THROTTLE BODY AIR FLOW
The PCM cannot detect a clogged or restricted air
cleaner inlet or filter element.
VACUUM ASSIST
The PCM cannot detect leaks or restrictions in the
vacuum circuits of vacuum assisted engine control
system devices. However, these could cause the PCM
to store a MAP sensor diagnostic trouble code and
cause a high idle condition.
PCM SYSTEM GROUND
The PCM cannot determine a poor system ground.
However, one or more diagnostic trouble codes may
be generated as a result of this condition. The mod-
ule should be mounted to the body at all times, also
during diagnostic.
PLEMISSION CONTROL SYSTEMS 25 - 23
DESCRIPTION AND OPERATION (Continued)

EVAPORATIVE EMISSION CONTROLS
TABLE OF CONTENTS
page page
DESCRIPTION AND OPERATION
EVAPORATION CONTROL SYSTEM..........25
EVAP CANISTER.........................25
PROPORTIONAL PURGE SOLENOIDÐPCM
OUTPUT..............................25
LEAK DETECTION PUMP..................26
LEAK DETECTION PUMP PRESSURE
SWITCH..............................27
POSITIVE CRANKCASE VENTILATION (PCV)
SYSTEMS.............................28POSITIVE CRANKCASE VENTILATION VALVE. . . 28
VEHICLE EMISSION CONTROL
INFORMATION LABEL...................29
REMOVAL AND INSTALLATION
EVAP CANISTER.........................29
LEAK DETECTION PUMP..................30
PROPORTIONAL PURGE SOLENOID VALVE....30
DESCRIPTION AND OPERATION
EVAPORATION CONTROL SYSTEM
OPERATION
The evaporation control system prevents the emis-
sion of fuel tank vapors into the atmosphere. When
fuel evaporates in the fuel tank, the vapors pass
through vent hoses or tubes to an activated carbon
filled evaporative canister. The canister temporarily
holds the vapors. The Powertrain Control Module
(PCM) allows intake manifold vacuum to draw
vapors into the combustion chambers during certain
operating conditions.
All engines use a proportional purge solenoid sys-
tem. The PCM controls vapor flow by operating the
purge solenoid. Refer to Proportional Purge Solenoid
in this section.
NOTE: The evaporative system uses specially man-
ufactured hoses. If they need replacement, only use
fuel resistant hose. Also the hoses must be able to
pass an Ozone compliance test.
NOTE: For more information on Onboard Refueling
Vapor Recovery (ORVR), refer to the Fuel Delivery
section.
EVAP CANISTER
DESCRIPTION
The vacuum and vapor tubes connect to the top of
the canister (Fig. 1).
OPERATION
All vehicles use a, maintenance free, evaporative
(EVAP) canister. Fuel tank vapors vent into the can-
ister. The canister temporarily holds the fuel vapors
until intake manifold vacuum draws them into the
combustion chamber. The Powertrain Control Module
(PCM) purges the canister through the proportional
purge solenoid. The PCM purges the canister at pre-
determined intervals and engine conditions.
Purge Free Cells
Purge-free memory cells are used to identify the
fuel vapor content of the evaporative canister. Since
the evaporative canister is not purged 100% of the
time, the PCM stores information about the evapora-
tive canister's vapor content in a memory cell.
The purge-free cells are constructed similar to cer-
tain purge-normal cells. The purge-free cells can be
monitored by the DRB III Scan Tool. The only differ-
ence between the purge-free cells and normal adap-
tive cells is that in purge-free, the purge is
completely turned off. This gives the PCM the ability
to compare purge and purge-free operation.
PROPORTIONAL PURGE SOLENOIDÐPCM
OUTPUT
DESCRIPTION
OPERATION
All vehicles use a proportional purge solenoid. The
solenoid regulates the rate of vapor flow from the
EVAP canister to the throttle body. The PCM oper-
ates the solenoid.
During the cold start warm-up period and the hot
start time delay, the PCM does not energize the sole-
noid. When de-energized, no vapors are purged.
PLEMISSION CONTROL SYSTEMS 25 - 25

The proportional purge solenoid operates at a fre-
quency of 200 hz and is controlled by an engine con-
troller circuit that senses the current being applied
to the proportional purge solenoid (Fig. 2) and then
adjusts that current to achieve the desired purge
flow. The proportional purge solenoid controls the
purge rate of fuel vapors from the vapor canister and
fuel tank to the engine intake manifold.
LEAK DETECTION PUMP
DESCRIPTION
The leak detection pump is a device used to detect
a leak in the evaporative system.
The pump contains a 3 port solenoid, a pump that
contains a switch, a spring loaded canister vent valve
seal, 2 check valves and a spring/diaphragm.
OPERATION
Immediately after a cold start, when the engine
temperature is between 40ÉF and 86ÉF, the 3 port
solenoid is briefly energized. This initializes the pump
by drawing air into the pump cavity and also closes
the vent seal. During non-test test conditions, the
vent seal is held open by the pump diaphragm assem-
bly which pushes it open at the full travel position.
The vent seal will remain closed while the pump is
cycling. This is due to the operation of the 3 port sole-
noid which prevents the diaphragm assembly from
reaching full travel. After the brief initialization
period, the solenoid is de-energized, allowing atmo-
spheric pressure to enter the pump cavity. This per-
mits the spring to drive the diaphragm which forces
air out of the pump cavity and into the vent system.
When the solenoid is energized and de-energized, the
cycle is repeated creating flow in typical diaphragm
pump fashion. The pump is controlled in 2 modes:
1 ± FUEL CAP
2 ± RECIRCULATION TUBE
3 ± LIQUID SEPARATOR
4 ± PURGE
5 ± W/LDP
6 ± BREATHER ELEMENT
7 ± W/O LDP8 ± CANISTER
9 ± ROLLOVER VALVE
10 ± FUEL TANK
11 ± CHECK VALVE
12 ± LIQUID TRAP
13 ± CONTROL VALVE
ORVR System Schematic
25 - 26 EMISSION CONTROL SYSTEMSPL
DESCRIPTION AND OPERATION (Continued)

PUMP MODE:The pump is cycled at a fixed rate
to achieve a rapid pressure build in order to shorten
the overall test time.
TEST MODE:The solenoid is energized with a
fixed duration pulse. Subsequent fixed pulses occur
when the diaphragm reaches the switch closure
point.
The spring in the pump is set so that the system
will achieve an equalized pressure of about 7.5 inches
of water.
When the pump starts, the cycle rate is quite high.
As the system becomes pressurized, pump rate drops.
If there is no leak, the pump will quit. If there is a
leak, the test is terminated at the end of the test
mode.If there is no leak, the purge monitor is run. If the
cycle rate increases due to the flow through the
purge system, the test is passed and the diagnostic is
complete.
The canister vent valve will unseal the system
after completion of the test sequence as the pump
diaphragm assembly moves to the full travel position.
LEAK DETECTION PUMP PRESSURE SWITCH
OPERATION
The leak detection pump LDP assembly incorpo-
rates two primary functions: it detects a leak in the
evaporative system, and it seals the evaporative sys-
tem so that the required leak detection monitor test
can be run.
The primary components within the leak detection
pump assembly are: a three-port leak detection sole-
noid valve, a pump assembly that includes a spring
loaded diaphragm, a reed switch which is used to
monitor the pump diaphragm movement (position),
two check valves, and a spring loaded vent seal
valve.
The three-port LDP solenoid valve is used to
expose either engine vacuum or atmospheric pressure
to the top side of the leak detection pump diaphragm.
When the LDP solenoid valve is deenergized its
port (opening) to engine vacuum is blocked off. This
allows ambient air (atmospheric pressure) to enter
the top of the pump diaphragm. The spring load on
the diaphragm will push the diaphragm down, as
long as there is no pressure present in the rest of the
evaporative system. If there is sufficient evaporative
system pressure present, then the pump diaphragm
will stay in the ªupº position. If the evaporative sys-
tem pressure decays, then the pump diaphragm will
eventually fall. The rate of this decent is dependent
upon the size of the evaporative system leak (Large
or small).
When the LDP solenoid valve is energized the port
(opening) to atmosphere is blocked off. At the same
time, the port to engine vacuum is opened. Engine
vacuum replaces atmospheric pressure. When engine
vacuum is sufficient, it over comes the spring pres-
sure load on the pump diaphragm and causes the
diaphragm to rise to its ªupº position. The reed
switch will change state depending upon the position
of the pump diaphragm.
If the diaphragm is in the ªupº position the reed
switch will be in its ªopenº state. This means that
the 12 volt signal sense to the PCM is interrupted.
Zero volts is detected by the PCM. If the pump dia-
phragm is in the ªdownº position the reed switch will
be in its ªclosedº state. 12 volts is sent to the PCM
via the switch sense circuit.
Fig. 1 EVAP Canister
Fig. 2 Proportional Purge Solenoid
PLEMISSION CONTROL SYSTEMS 25 - 27
DESCRIPTION AND OPERATION (Continued)

The check valves are one-way valves. The first
check valve is used to draw outside air into the lower
chamber of the LDP (the space that is below the
pump diaphragm). The second check valve is used to
vent this outside air, which has become pressurized
from the fall of the pump diaphragm, into the evap-
orative system.
The spring loaded vent seal valve, inside the LDP
is used to seal off the evaporative system. When the
pump diaphragm is in the ªupº position the spring
pushes the vent seal valve closed. The vent seal valve
opens only when the pump diaphragm is in its ªfull
downº position. When the pump assembly is in its
pump mode the pump diaphragm is not allowed to
descend (fall) so far as to allow the vent seal valve to
open. This allows the leak detection pump to develop
the required pressure within the evaporative system
for system leak testing.
A pressure build up within the evaporative system
may cause pressure on the lower side of the LDP dia-
phragm. This will cause the LDP diaphragm to
remain in its ªupº position (stuck in the up position).
This condition can occur even when the solenoid
valve is deenergized. This condition can be caused by
previous cycling (pumping) of the LDP by the techni-
cian (dealer test). Another way that this condition is
created is immediately following the running of the
vehicle evaporative system monitor. In this case, the
PCM has not yet opened the proportional purge sole-
noid in order to vent the pressure that has been built
up in the evaporative system to the engine combus-
tion system. The technician will need to vent the
evaporative system pressure via the vehicle fuel filler
cap and its fuel filler secondary seal (if so equipped
in the fuel filler neck). This will allow the technician
to cycle the LDP and to watch switch state changes.
After passing the leak detection phase of the test,
system pressure is maintained until the purge sys-
tem is activated, in effect creating a leak. If the dia-
phragm falls (as is expected), causing the reed switch
to change state, then the diagnostic test is completed.
When of the evaporative system leak monitor
begins its various tests, a test is performed to deter-
mine that no part of the evaporative system is
blocked. In this test, the LDP is cycled (pumped) a
calibrated (few) number of times. Pressure should not
build up in the evaporative system. If pressure is
present, then LDP diaphragm is forced to stay in its
ªupº position. The reed switch now stays open and
the PCM senses this open (incorrect) state. The evap-
orative system monitor will fail the test because of a
detected obstruction within the system.
Possible causes:
²Open or shorted LDP switch sense circuit
²Leak Detection Pump switch failure²Open fused ignition switch output
²Restricted, disconnected, or blocked manifold
vacuum source
²Obstruction of hoses or lines
²PCM failure
POSITIVE CRANKCASE VENTILATION (PCV)
SYSTEMS
DESCRIPTION
OPERATION
Intake manifold vacuum removes crankcase vapors
and piston blow-by from the engine. The emissions
pass through the PCV valve into the intake manifold
where they become part of the calibrated air-fuel
mixture. They are burned and expelled with the
exhaust gases. The air cleaner supplies make up air
when the engine does not have enough vapor or
blow-by gases. In this system, fresh air does not
enter the crankcase.
POSITIVE CRANKCASE VENTILATION VALVE
OPERATION
The PCV valve contains a spring loaded plunger.
The plunger meters the amount of crankcase vapors
routed into the combustion chamber based on intake
manifold vacuum.
When the engine is not operating or during an
engine backfire, the spring forces the plunger back
against the seat. This prevents vapors from flowing
through the valve (Fig. 4).
When the engine is at idle or cruising, high mani-
fold vacuum is present. At these times manifold vac-
uum is able to completely compress the spring and
Fig. 3 PCV System
25 - 28 EMISSION CONTROL SYSTEMSPL
DESCRIPTION AND OPERATION (Continued)

HEATING AND AIR CONDITIONING
TABLE OF CONTENTS
page page
GENERAL INFORMATION
A/C APPLICATION TABLE...................2
HEATER AND AIR CONDITIONING CONTROL...2
HEATER AND AIR CONDITIONING............2
INTRODUCTION..........................3
SAFETY PRECAUTIONS AND WARNINGS......4
DESCRIPTION AND OPERATION
A/C REFRIGERANT LINES..................4
BLOWER MOTOR RESISTOR................5
COMPRESSOR...........................5
COMPRESSOR FRONT SHAFT SEAL..........6
CONDENSATION DRAIN TUBE...............6
ENGINE COOLING SYSTEM REQUIREMENTS...6
EVAPORATOR PROBE......................6
HANDLING TUBING AND FITTINGS...........6
HIGH PRESSURE CUT OUT SWITCH..........6
LOW PRESSURE CUT OFF SWITCH..........6
SIDE WINDOW DEMISTERS................7
SYSTEM AIRFLOW........................7
SYSTEM OIL LEVEL.......................7
VACUUM CONTROL SYSTEM................8
DIAGNOSIS AND TESTING
A/C PERFORMANCE TEST..................9
BLOWER MOTOR ELECTRICAL DIAGNOSIS....9
BLOWER MOTOR VIBRATION AND/OR
NOISE DIAGNOSIS.....................11
COMPRESSOR NOISE DIAGNOSIS..........11
EVAPORATOR PROBE TEST................11
EXPANSION VALVE.......................11
HEATER PERFORMANCE TEST.............13
LOW PRESSURE CUT OFF SWITCH.........14
SYSTEM CHARGE LEVEL TEST.............14
VACUUM CONTROL SYSTEM...............15
SERVICE PROCEDURES
CHARGING A/C SYSTEM..................17EVACUATING REFRIGERANT SYSTEM........18
R-134a REFRIGERANT....................19
SERVICING REFRIGERANT OIL LEVEL.......19
SYSTEM LEAK CHECKING.................20
REMOVAL AND INSTALLATION
A/C FILTER/DRIER.......................20
A/C SERVICE PORT VALVE CORES..........21
BLOWER MOTOR AND WHEEL ASSEMBLY....21
BLOWER MOTOR RESISTOR...............22
BLOWER MOTOR WHEEL.................22
COMPRESSOR..........................22
COMPRESSOR CLUTCH/COIL ASSEMBLY.....23
CONDENSATION DRAIN TUBE..............25
CONDENSER............................25
DISCHARGE LINE........................26
EVAPORATOR...........................26
EVAPORATOR PROBE.....................26
EXPANSION VALVE.......................27
HEATER CORE..........................28
HEATER HOSES.........................28
HIGH PRESSURE CUT OUT SWITCH.........29
HIGH PRESSURE RELIEF VALVE............29
LIQUID LINE............................29
LOW PRESSURE CUT OFF SWITCH.........29
MODE CONTROL CABLE..................30
RECIRCULATION DOOR ACTUATOR.........31
SUCTION LINE..........................31
TEMPERATURE CONTROL CABLE...........32
UNIT HOUSING..........................32
DISASSEMBLY AND ASSEMBLY
HEATER-A/C HOUSING....................34
ADJUSTMENTS
MODE CONTROL CABLE..................34
TEMPERATURE CONTROL CABLE...........34
PLHEATING AND AIR CONDITIONING 24 - 1

SAFETY PRECAUTIONS AND WARNINGS
WARNING: WEAR EYE PROTECTION WHEN SER-
VICING THE AIR CONDITIONING REFRIGERANT
SYSTEM. SERIOUS EYE INJURY CAN RESULT
FROM EYE CONTACT WITH REFRIGERANT. IF EYE
CONTACT IS MADE, SEEK MEDICAL ATTENTION
IMMEDIATELY.
DO NOT EXPOSE REFRIGERANT TO OPEN
FLAME. POISONOUS GAS IS CREATED WHEN
REFRIGERANT IS BURNED. AN ELECTRONIC TYPE
LEAK DETECTOR IS RECOMMENDED.
LARGE AMOUNTS OF REFRIGERANT RELEASED
IN A CLOSED WORK AREA WILL DISPLACE THE
OXYGEN AND CAUSE SUFFOCATION.
THE EVAPORATION RATE OF REFRIGERANT AT
AVERAGE TEMPERATURE AND ALTITUDE IS
EXTREMELY HIGH. AS A RESULT, ANYTHING THAT
COMES IN CONTACT WITH THE REFRIGERANT
WILL FREEZE. ALWAYS PROTECT SKIN OR DELI-
CATE OBJECTS FROM DIRECT CONTACT WITH
REFRIGERANT. R-134a SERVICE EQUIPMENT OR
VEHICLE A/C SYSTEM SHOULD NOT BE PRES-
SURE TESTED OR LEAK TESTED WITH COM-
PRESSED AIR.
SOME MIXTURES OF AIR and R-134a HAVE BEEN
SHOWN TO BE COMBUSTIBLE AT ELEVATED
PRESSURES. THESE MIXTURES ARE POTENTIALLY
DANGEROUS AND MAY RESULT IN FIRE OR
EXPLOSION CAUSING INJURY OR PROPERTY
DAMAGE.
ANTIFREEZE IS AN ETHYLENE GLYCOL BASE
COOLANT AND IS HARMFUL IF SWALLOWED OR
INHALED. SEEK MEDICAL ATTENTION IMMEDI-
ATELY IF SWALLOWED OR INHALED. DO NOT
STORE IN OPEN OR UNMARKED CONTAINERS.
WASH SKIN AND CLOTHING THOROUGHLY AFTER
COMING IN CONTACT WITH ETHYLENE GLYCOL.
KEEP OUT OF REACH OF CHILDREN AND PETS.
DO NOT OPEN A COOLING SYSTEM WHEN THE
ENGINE IS AT RUNNING TEMPERATURE. PER-
SONAL INJURY CAN RESULT.
CAUTION: The engine cooling system is designed
to develop internal pressure of 97 to 123 kPa (14 to
18 psi). Allow the vehicle to cool a minimum of 15
minutes before opening the cooling system. Refer
to Group 7, Cooling System.
DESCRIPTION AND OPERATION
A/C REFRIGERANT LINES
DISCHARGE LINE
The discharge line is the line that goes from the
compressor to the condenser (Fig. 3). It has no ser-
viceable parts except the rubber O-rings. If the line
is found to be leaking or is damaged it must be
replaced as an assembly.
LIQUID LINE
The liquid line is the line that goes from the con-
denser to drier (Fig. 3). It has no serviceable parts
except the rubber O-rings. If the line is found to be
leaking or is damaged it must be replaced as an
assembly.
SUCTION LINE
The suction line is the large line that connects to
the expansion valve and goes to the compressor (Fig.
3). It also has a small line that goes to the filter/
drier. The suction line uses a gasket on the expan-
sion valve side and rubber O-rings on all other
connections.
There are no serviceable parts on the suction line
other than the rubber O-rings and expansion valve
gasket. If the line is found to be leaking or is dam-
aged it must be replaced as an assembly.
Fig. 3 A/C Compressor Lines
1 ± CONDENSER LIQUID LINE
2 ± SUCTION LINE
3 ± COMPRESSOR MANIFOLD SCREWS
4 ± COMPRESSOR
5 ± DISCHARGE LINE
24 - 4 HEATING AND AIR CONDITIONINGPL
GENERAL INFORMATION (Continued)

A/C SERVICE PORT VALVE CORES
The A/C service port valve cores are serviceable
items (Fig. 4). The high side valve is located on the
filter-drier, and the low side valve is situated on the
suction line, near the washer fluid reservoir filler.
BLOWER MOTOR RESISTOR
The blower motor resistor is located in the cowl, at
the base of the windshield (Fig. 5). There are two dif-
ferent resistor blocks depending on whether the vehi-
cle is equipped with A/C or not. The blower motor
resistors will get hot when in use (Fig. 6). Do not
touch resistor block if the blower motor has been
running.
COMPRESSOR
The compressor used on this vehicle is a Nippon-
denso 10S17. This compressor uses an aluminum
swash plate, teflon coated pistons and aluminum
sleeveless cylinder walls.
NOISE
Excessive noise that occurs when the air condition-
ing is being used may be caused by:
²Loose bolts
²Mounting brackets
²Loose compressor clutch
²Excessive high refrigerant operating pressureVerify the following before compressor repair is
performed:
(1) Compressor drive belt condition
(2) Proper refrigerant charge
(3) Thermal expansion valve (TXV) operating cor-
rectly
(4) Head pressure is normal
Fig. 4 A/C Service Port Valves
1 ± A/C SERVICE PORTS
2 ± FILTER/DRIER
Fig. 5 Blower Motor Resistor Block
1 ± RESISTOR BLOCK
2 ± ELECTRICAL CONNECTOR
Fig. 6 Blower Motor Resistors
1 ± RESISTOR BLOCK
2 ± RESISTORS
PLHEATING AND AIR CONDITIONING 24 - 5
DESCRIPTION AND OPERATION (Continued)