1996 CHRYSLER VOYAGER ECO mode

COOLDOWN TEST ENTRY
TO INITIATE TESTS:
²Set Blower motor ON HIGH
²Set Mode position to Panel
²Open all A/C outlets
²Set Temperature to Cold (Both slide pots if
equipped)
²Depress WASH and A/C simultaneously for 5
Seconds
NOTE: Prior to start of test, If the evaporator is
already cold, the system will fail test. To correct,
operate system with A/C OFF and the blower motor
ON high for three minutes prior to starting test.
RESULTS:
²All LED's will turn on for 5 Seconds
²Cooldown Test is running when A/C and
RECIRC. are alternately flashing. If A/C and
RECIRC. are flashing simultaneously, Cooldown has
failed.
CALIBRATION DIAGNOSTICS AND
COOLDOWN ABORT
Test can be aborted by doing one of the following:
²Depressing Rear Window Defogger, RECIRC and
Rear Wiper buttons.²Cycling Ignition OFF and then ON.
²Control will automatically abort after 15 min-
utes from the time Calibration Diagnostics and
Cooldown was entered.
The HVAC control module will return to normal
operation or may indicate unsuccessful Calibration
Diagnostics or Cooldown test by LED's flashing
simultaneously.
EEPROM DATA
Calibration Diagnostics, Cooldown Status and
evaporator temperature Fin Sensor values are stored
in an EEPROM memory internal to the control. The
microcomputer within the HVAC control module uses
this information:
²To determine if Cooldown needs to run
²For proper position of the Heater-A/C unit
assembly doors
ACTUATOR CALIBRATION AND
DIAGNOSTICS.
NOTE: Do not run actuators unless they are prop-
erly mounted on the HVAC control module.
Actuator end point calibration takes approximately
60 seconds. The REAR WIPER and INTERMITTENT
LED's will flash alternately during the test. The con-
trol will cycle the Blend actuator(s) to the Heat stop
first then back to Cold. After the Blend actuator(s)
have been calibrated the Mode actuator will be cycled
to Defrost and then to Panel. Successful calibration
is defined as actuator travel falling within their min-
imum and maximum limits.
BLEND/PASSENGER ACTUATOR BACKGROUND
The Blend/Passenger Actuator can move the tem-
perature door in two directions. When the voltage at
Pin 12 of the control module is high, about 11.5 volts,
and the voltage at Pin 17 is low, about 1.5 volts, the
door will move towards the Heat position. When Pin
17 is High and Pin 12 is Low the door will move
towards the Cold position. When both Pins are high
or both Pins are low, the actuator will not move. The
Blend/Passenger feedback signal is a voltage signal
that is supplied by the actuator to the control. The
signal will be about 4.0 volts in the Heat position
and 1.0 volt in the Cold position. As the position of
the Blend/Passenger actuator changes, so will the
feedback signal. The feedback signal is necessary for
the correct positioning of the temperature door.
DRIVER ACTUATOR BACKGROUND
The Driver Actuator can move the temperature
door in two directions. When the voltage at Pin 15 of
the control module is high, about 11.5 volts, and the
voltage at Pin 13 is low, about 1.5 volts the door will
LED'S PASS/FAILCORRECTIVE
ACTION
NO LED'S
FLASHING-
NORMAL
OPERATIONPASSED
CALIBRATION,
DIAGNOSTICS
AND
COOLDOWNNONE
REAR WIPER
AND
INTERMITTENT
LED'S FLASH
SIMULTANEOUSLYFAILED
CALIBRATION
DIAGNOSTICSRUN
CALIBRATION
TEST
A/C AND RECIRC
LED'S FLASH
SIMULTANEOUSLYFAILED
COOLDOWNRUN
COOLDOWN
TEST
REAR WIPER
AND
INTERMITTENT
LED'S ARE
FLASHING
SIMULTANEOUSLY
A/C AND RECIRC
LED'S ARE
FLASHING
SIMULTANEOUSLYFAILED
CALIBRATION,
DIAGNOSTICS
AND FAILED
COOLDOWN
TESTRUN
CALIBRATION
TEST
NS/GSHEATING AND AIR CONDITIONING 24 - 7
DIAGNOSIS AND TESTING (Continued)

²Set A/C to ON, if A/C Clutch does not engage
make sure Fail Codes 5 and 6 are cleared.To clear
the error code 5 and 6 the evaporator probe and/or
the wiring repair needs to be completed. Then, press
and hold the intermittent wipe button for 5 seconds.
²Run Diagnostics (Depress REAR WIPER and
REAR WASH)
²When Diagnostics is complete, Cycle to Level 4.
Display Sequence is as follows:
²REAR WIPER LED will display the Level
²INTERMITTENT LED will display ten's digit
²Short Pause
²INTERMITTENT LED will display the one's
digit.
The HVAC control module will continue to cycle
the Level and then Temperature until the level is
changed or Calibration Diagnostics and Cooldown
test is exited.
HVAC CONTROL DIAGNOSTIC CONDITIONS
For wiring circuits, wiring connectors, and Pin
numbers, refer to Group 8W, Wiring Diagrams.
After calibration, Rear Wiper LED flashing
once, Intermittent LED not flashing.
The system has passed calibration. Press the Rear
Wiper button to exit calibration.
After calibration, Rear Wiper LED flashing
once, Intermittent LED flashing once. The
mode actuator did not reach defrost position.
(1) Using a voltmeter, check the mode door actua-
tor wiring connector. Check Pin 1 for battery voltage.
Move the HVAC control from the defrost to panel
position, and check Pin 6 voltage it should change
from 0.5 - 1 volts to 3.5 - 4.5 volts. If voltage is OK,
go to Step 2. If not OK, check for loose or corroded
connector, open or shorted circuit and repair as nec-
essary.
(2) Remove actuator, and check if the gear pins are
in the correct track on cam or if they are binding. If
OK, go to Step 3. If not OK, repair as necessary.
(3) Check for binding door, if door is binding repair
as necessary. If gears and door are OK, replace
actuator.
(4) Once repairs are completed repeat the Calibra-
tion Diagnostic and Cooldown test. Repeating the
test is necessary to clear the fault codes.
After calibration, Rear Wiper LED flashing
once, Intermittent LED flashing twice. The
mode actuator did not reach panel position.
(1) Using a voltmeter, check the mode door actua-
tor wiring connector. Check Pin 1 for battery voltage.
Move the HVAC control from panel to defrost posi-
tion, and check Pin 6 voltage it should change from
3.5 - 4.5 volts to 0.5 - 1 volts. If voltage is OK, go toStep 2. If not OK, check for loose or corroded connec-
tor, open or shorted circuit and repair as necessary.
(2) Remove actuator, and check if the gear pins are
in the correct cam track or binding. If OK, go to Step
3. If not OK, repair as necessary.
(3) Check for binding door, if door is binding repair
as necessary. If gears and door are OK, replace
actuator.
(4) Once repairs are completed repeat the Calibra-
tion Diagnostic and Cooldown test. Repeating the
test is necessary to clear the fault codes.
After calibration, Rear Wiper LED flashing
once, Intermittent LED flashing three times.
The main temperature actuator/passenger
temperature actuator on a zone system did
not reach cold stop.
(1) Check if the correct HVAC control module was
used.
(2) Using a voltmeter, check the temperature door
actuator wiring connector. Check Pin 1 for battery
voltage. Move the HVAC control from the cold to hot
position, and check Pin 5 voltage it should change
from 0.5 - 4 volts to 3.5 - 4.5 volts. If voltage is OK,
go to Step 3. If not OK, check for loose or corroded
connector, open or shorted circuit and repair as nec-
essary.
(3) Remove actuator, and check if gear pins are in
the correct cam track or binding. If OK, go to Step 4.
If not OK, repair as necessary.
(4) Check for binding door, if door is binding repair
as necessary. If gears and door are OK, replace
actuator.
(5) Once repairs are completed repeat the Calibra-
tion Diagnostic and Cooldown test. Repeating the
test is necessary to clear the fault codes.
After calibration, Rear Wiper LED flashing
once, Intermittent LED flashing four times.
The main temperature actuator/passenger
temperature actuator on a zone system did
not reach hot stop.
(1) Check if the correct HVAC control module was
used.
(2) Using a voltmeter, check the temperature door
actuator wiring connector. Check Pin 1 for battery
voltage. Move the HVAC control from hot to cold
position and check Pin 5 voltage it should change
from 3.5 -4.5 volts 0.5 - 1.5 volts. If voltage is OK, go
to Step 3. If not OK, check for loose or corroded con-
nector, open or shorted circuit and repair as neces-
sary.
(3) Remove actuator, and check if the gear pins are
in the correct track on cam or if they are binding. If
OK, go to Step 4. If not OK, repair as necessary.
NS/GSHEATING AND AIR CONDITIONING 24 - 9
DIAGNOSIS AND TESTING (Continued)

POSSIBLE LOCATIONS OR CAUSE OF
OBSTRUCTED COOLANT FLOW
(1) Pinched or kinked heater hoses.
(2) Improper heater hose routing.
(3) Plugged heater hoses or supply and return
ports at cooling system connections, refer to Group 7,
Cooling System.
(4) Plugged heater core.
(5) Air locked heater core.
(6) If coolant flow is verified and outlet tempera-
ture is insufficient, a mechanical problem may exist.
POSSIBLE LOCATION OR CAUSE OF
INSUFFICIENT HEAT
(1) Obstructed cowl air intake.
(2) Obstructed heater system outlets.
(3) Blend-air door not functioning properly.
TEMPERATURE CONTROL
If temperature cannot be adjusted with the TEMP
lever on the control panel, the following could require
service:
(1) Blend-air door binding.
(2) Faulty blend-air door motor.
(3) Improper engine coolant temperature.
(4) Faulty Instrument Panel Control.
SYSTEM CHARGE LEVEL TEST
The procedure below should be used to check
and/or fill the refrigerant charge in the air condition-
ing system.
NOTE: The amount of R134a refrigerant that the air
conditioning system holds is 0.96 kg (34 oz. or 2.13
lbs.).
NOTE: Low Charge, condition may be described
as:
²Loss of A/C performance
²Fog from A/C outlets
²evaporator may have a HISS sound
There are two different ways the system can be
tested:
²With a scan tool (DRB), thermocouple and the
Charge Determination Graph. Use the scan tool
(DRB) diagnostic topic: Engine±System Monitors, A/C
Pressure.
²Using a manifold gauge set, a thermocouple and
the Charge Determination Graph.
It is recommended to use the gauges or reclaim/re-
cycle equipment.
WARNING: AVOID BREATHING A/C REFRIGERANT
AND LUBRICANT VAPOR OR MIST. EXPOSURE MAY
IRRITATE EYES, NOSE AND THROAT. USE ONLY
APPROVED SERVICE EQUIPMENT MEETING SAEREQUIREMENTS TO DISCHARGE R-134a SYSTEM. IF
ACCIDENTAL SYSTEM DISCHARGE OCCURS, VEN-
TILATE WORK AREA BEFORE RESUMING SERVICE.
R-134a SERVICE EQUIPMENT OR VEHICLE A/C
SYSTEM SHOULD NOT BE PRESSURE TESTED OR
LEAK TESTED WITH COMPRESSED AIR. SOME
MIXTURES OF AIR/R-134a HAVE BEEN SHOWN TO
BE COMBUSTIBLE AT ELEVATED PRESSURES.
THESE MIXTURES ARE POTENTIALLY DANGER-
OUS AND MAY RESULT IN FIRE OR EXPLOSION
CAUSING INJURY OR PROPERTY DAMAGE.
(1) Establish your preferred method of measuring
liquid line pressure. Use a manifold gauge set or a
DRB scan tool.
(2) A
ttach a clamp-on thermocouple (Professional
Service Equipment 66-324-0014 or 80PK-1A) or equiv-
alent to the liquid line. It must be placed as close to
the A/C Pressure Transducer as possible to observe liq-
uid line temperature. Refer to ªThermocouple Probeº in
this section for more information on probe.
(3) The vehicle must be in the following modes:
²Transaxle in Park
²Engine Idling at 700 rpm
²A/C Controls Set to Outside Air
²Panel Mode
²Full Cool
²High Blower motor, (vehicle equipped with rear
A/C turn rear blower motor ON HIGH)
²A/C Button in the ON position
²Vehicle Windows Open.
²Recirc. button turned OFF
(4) Operate system for a couple of minutes to allow
the system to stabilize.
(5) Set system pressure to about 1793 kPa (260
psi) by placing a piece of cardboard over part of the
front side of the condenser. To place cardboard prop-
erly, remove the upper radiator-condenser cover.
Insert cardboard between condenser and radiator
front. This will maintain a constant pressure.
(6) Observe Liquid Line pressure and Liquid line
temperature. Using theCharge Determination
Chartdetermine where the system is currently oper-
ating. If the system is in the undercharged region,
ADD 0.057 Kg. (2 oz.) to the system and recheck
readings. If the system is in the overcharged region,
RECLAIM 0.057 Kg. (2 oz.) from the system and
recheck readings. Continue this process until the sys-
tem readings are in the proper charge area on the
Charge Determination Chart.
(7) The same procedure can be performed using
the scan tool (DRB). To determine liquid line pres-
sure, attach the scan tool, go to System Moni-
tors±A/C Pressure. Observe liquid line pressure from
A/C Pressure Transducer on digital display and digi-
tal thermometer. Refer toCharge Determination
Chartand determine where the system is operating.
NS/GSHEATING AND AIR CONDITIONING 24 - 15
DIAGNOSIS AND TESTING (Continued)

MODE DOOR ACTUATOR
REMOVAL
(1) Remove the lower left side steering column
cover. Refer to Group 8E, Instrument Panel and Sys-
tems.
(2) Remove ABS control module (Fig. 40).
(3) Remove mode actuator connector (Fig. 41).
(4) Remove mode door actuator (Fig. 42).
INSTALLATION
(1) For installation, reverse the above procedures.
(2) Perform the HVAC control Calibration Diagnos-
tic and Cooldown test.
SIDE WINDOW DEMISTER DUCTS
LEFT SIDE
The LEFT side window demister duct is a two
piece design. The left side has a long duct that
attaches to an intermediate duct and then to the dis-tribution housing. The duct is located on top of the
instrument panel. To service the duct, remove the I/P
cover and remove duct retainers/fasteners. (Fig. 43).
RIGHT SIDE
The demister duct on the right side is a one piece
design. It is one long duct that attaches to the distri-
bution housing. The duct is located on top of the
instrument panel and it is not serviceable (Fig. 44).
SUCTION LINE
REMOVAL
(1) Disconnect the battery negative cable.
(2) Recover A/C system refrigerant.
(3) Remove ground wire at dash panel.
(4) Remove the nut retaining the refrigerant line
sealing plate to the expansion valve (Fig. 27).
(5) Remove the stud from the expansion valve (Fig.
28).
(6) Remove suction line from expansion valve.
Fig. 40 ABS Control Module
Fig. 41 Mode Door Actuator Connector
Fig. 42 Mode Door Actuator
Fig. 43 Left Side Demister Duct
NS/GSHEATING AND AIR CONDITIONING 24 - 29
REMOVAL AND INSTALLATION (Continued)

cranking. Whenever the Powertrain Control Module
(PCM) sets a Diagnostic Trouble Code (DTC) that
affects vehicle emissions, it illuminates the MIL. If a
problem is detected, the PCM sends a message over
the CCD Bus to the instrument cluster to illuminate
the lamp. The PCM illuminates the MIL only for
DTC's that affect vehicle emissions. The MIL stays
on continuously when the PCM has entered a
Limp-In mode or identified a failed emission compo-
nent or system. The MIL remains on until the DTC
is erased. Refer to the Diagnostic Trouble Code
charts in this group for emission related codes.
Also, the MIL either flashes or illuminates contin-
uously when the PCM detects active engine misfire.
Refer to Misfire Monitoring in this section.
Additionally, the PCM may reset (turn off) the MIL
when one of the following occur:
²PCM does not detect the malfunction for 3 con-
secutive trips (except misfire and fuel system moni-
tors).
²PCM does not detect a malfunction while per-
forming three successive engine misfire or fuel sys-
tem tests. The PCM performs these tests while the
engine is operating within6375 RPM of and within
10 % of the load of the operating condition at which
the malfunction was first detected.
STATE DISPLAY TEST MODE
The switch inputs to the Powertrain Control Mod-
ule (PCM) have two recognized states; HIGH and
LOW. For this reason, the PCM cannot recognize the
difference between a selected switch position versus
an open circuit, a short circuit, or a defective switch.
If the State Display screen shows the change from
HIGH to LOW or LOW to HIGH, assume the entire
switch circuit to the PCM functions properly. From
the state display screen, access either State Display
Inputs and Outputs or State Display Sensors.
STATE DISPLAY INPUTS AND OUTPUTS
Connect the DRB scan tool to the data link connec-
tor and access the State Display screen. Then access
Inputs and Outputs. The following list contains the
PCM system functions accessible through the Inputs
and Outputs screen.
Park/Neutral Switch
Speed Control Resume
Brake Switch
Speed Control On/Off
Speed Control Set
S/C Vent Solenoid
Actual S/C Vent Sol.
S/C Vacuum Solenoid
Actual S/C Vacuum Sol.
S/C Cancel
S/C Last Cutout
S/C Working Status
S/C Denied Status
A/C Clutch Relay
Actual A/C Clutch Relay
EGR Solenoid
Actual EGR Sol.
Automatic Shutdown Relay
Actual Automatic Shutdown Relay
Automatic Shutdown Relay Sense
Radiator Fan Control Module
Actual Radiator Fan Control Module
Duty Cycle EVAP Purge Solenoid
Actual EVAP Purge Sol.
Torque Converter Clutch Solenoid
Power Steering Switch
Closed Loop State
Current CMP Edge
Current CKP State
Current Sync State
Fuel Pump Relay
Actual Fuel Pump Relay
Ignition Sense (A21)
Malfunction Lamp
Limp-in Reason
STATE DISPLAY SENSORS
Connect the DRB scan tool to the vehicle and
access the State Display screen. Then access Sensor
Display. The following list contains the PCM system
functions accessible through the Sensor Display
screen.
Battery Temperature
Engine Coolant Temperature
Engine Coolant Temp Sensor
Throttle Position Volts
Minimum Throttle
Knock Sensor Volts
Battery Voltage
MAP Sensor Reading
Idle Air Control Motor Position
Fig. 1 Data Link (Diagnostic) Connector
25 - 2 EMISSION CONTROL SYSTEMSNS
DESCRIPTION AND OPERATION (Continued)

Adaptive Fuel Factor
Barometric Pressure
Engine Speed
Module Spark Advance
Speed Control Target
Intake Air Temp Degrees
Intake Air Temp Volts
Charging System Goal
Theft Alarm Status
Map Sensor Voltage
Vehicle Speed
Throttle Opening (percentage)
TPS Calculated
Cam Timing Position
Target Idle
Time From Start To Run
Run Time At Stall
Injector Pulse-width
Upstream O2S Volts
Downstream O2S Volts
Closed Loop Timer
Short Term Adaptive
Current Adaptive Cell
Adaptive Memory Cell 0
Adaptive Memory Cell 1
Adaptive Memory Cell 2
Adaptive Memory Cell 3
Adaptive Memory Cell 4
Adaptive Memory Cell 5
Adaptive Memory Cell 6
Adaptive Memory Cell 7
Adaptive Memory Cell 8
Adaptive Memory Cell 9
Adaptive Memory Cell 10
Adaptive Memory Cell 11
Adaptive Memory Cell 12
Adaptive Memory Cell 13
Adaptive Memory Cell 14
Adaptive Memory Cell 15
Purge Free Idle Cell
Purge Free Cell 2 (corresponds to memory cell 2)
Purge Free Cell 3 (corresponds to memory cell 5)
Target IAC Steps
Retard Cylinder (1)
Retard Cylinder (2)
Retard Cylinder (3)
Retard Cylinder (4)
Retard Cylinder (5)
Retard Cylinder (6)CIRCUIT ACTUATION TEST MODE
The Circuit Actuation Test Mode checks for proper
operation of output circuits or devices the Powertrain
Control Module (PCM) may not internally recognize.
The PCM attempts to activate these outputs and
allow an observer to verify proper operation. Most of
the tests provide an audible or visual indication of
device operation (click of relay contacts, fuel spray,
etc.). Except for intermittent conditions, if a device
functions properly during testing, assume the device,
its associated wiring, and driver circuit work cor-
rectly.
DIAGNOSTIC TROUBLE CODES
A Diagnostic Trouble Code (DTC) indicates the
PCM has recognized an abnormal condition in the
system.
The preferred and most accurate method of retriev-
ing a DTC is by using the DRB scan tool. The scan
tool supplies detailed diagnostic information which
can be used to more accurately diagnose causes for a
DTC.
Remember that DTC's are the results of a sys-
tem or circuit failure, but do not directly iden-
tify the failed component or components.
NOTE: For a list of DTC's, refer to the charts in this
section.
BULB CHECK
Each time the ignition key is turned to the ON
position, the malfunction indicator (check engine)
lamp on the instrument panel should illuminate for
approximately 2 seconds then go out. This is done for
a bulb check.
OBTAINING DTC'S USING DRB SCAN TOOL
(1) Connect the DRB scan tool to the data link
(diagnostic) connector. This connector is located in
the passenger compartment; at the lower edge of
instrument panel; near the steering column.
(2) Turn the ignition switch on and access the
ªRead Faultº screen.
(3) Record all the DTC's and ªfreeze frameº infor-
mation shown on the DRB scan tool.
(4) To erase DTC's, use the ªErase Trouble Codeº
data screen on the DRB scan tool.Do not erase any
DTC's until problems have been investigated
and repairs have been performed.
NSEMISSION CONTROL SYSTEMS 25 - 3
DESCRIPTION AND OPERATION (Continued)

components now have input (rationality) and output
(functionality) checks. Previously, a component like
the Throttle Position sensor (TPS) was checked by
the PCM for an open or shorted circuit. If one of
these conditions occurred, a DTC was set. Now there
is a check to ensure that the component is working.
This is done by watching for a TPS indication of a
greater or lesser throttle opening than MAP and
engine rpm indicate. In the case of the TPS, if engine
vacuum is high and engine rpm is 1600 or greater
and the TPS indicates a large throttle opening, a
DTC will be set. The same applies to low vacuum
and 1600 rpm.
Any component that has an associated limp in will
set a fault after 1 trip with the malfunction present.
Refer to the Diagnostic Trouble Codes Description
Charts in this section and the appropriate Power-
train Diagnostic Procedure Manual for diagnostic
procedures.
NON-MONITORED CIRCUITS
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.
PCM CONNECTOR ENGAGEMENT
The PCM may not be able to determine spread or
damaged connector pins. However, it might store
diagnostic trouble codes as a result of spread connec-
tor pins.
HIGH AND LOW LIMITS
The PCM compares input signal voltages from each
input device with established high and low limits for
the device. If the input voltage is not within limits
and other criteria are met, the PCM stores a diagnos-
tic trouble code in memory. Other diagnostic trouble
code criteria might include engine RPM limits or
input voltages from other sensors or switches that
must be present before verifying a diagnostic trouble
code condition.
NSEMISSION CONTROL SYSTEMS 25 - 11
DESCRIPTION AND OPERATION (Continued)

The proportional purge solenoid operates at a fre-
quency of 200hz and is controlled by an engine con-
troller circuit that senses the current being applied
to the proportional purge solenoid 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.
PRESSURE-VACUUM FILLER CAP
CAUTION: Remove the fuel filler cap to relieve fuel
tank pressure. The cap must be removed prior to
disconnecting any fuel system component or ser-
vicing the fuel tank.
A pressure-vacuum relief cap seals the fuel tank
(Fig. 3). Tightening the cap on the fuel filler tube
forms a seal between them. The relief valves in the
cap are a safety feature. They prevent possible exces-
sive pressure or vacuum in the tank. Excessive fuel
tank pressure could be caused by a malfunction in
the system or damage to the vent lines.
The seal between the cap and filler tube breaks
when the cap is removed and relieves fuel tank pres-
sure.
If the filler cap needs replacement, only use the
correct part.
LEAK DETECTION PUMP
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.
Immediately after a cold start, when the engine
temperature is between 40ÉF and 86ÉF, the 3 portsolenoid 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
assembly which pushes it open at the full travel posi-
tion. The vent seal will remain closed while the
pump is cycling. This is due to the operation of the 3
port solenoid which prevents the diaphragm assem-
bly from reaching full travel. After the brief initial-
ization period, the solenoid is de-energized, allowing
atmospheric pressure to enter the pump cavity. This
permits 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-ener-
gized, the cycle is repeated creating flow in typical
diaphragm pump fashion. The pump is controlled in
2 modes:
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.
Fig. 2 Proportional Purge Solenoid
Fig. 3 Pressure Vacuum Filler Cap
25 - 14 EMISSION CONTROL SYSTEMSNS
DESCRIPTION AND OPERATION (Continued)