stop start CHRYSLER VOYAGER 2001 Workshop Manual

(5) Low line pressure in all positions indicates a
defective pump, a clogged filter, or a stuck pressure
regulator valve.
GOVERNOR PRESSURE
Test only if transaxle shifts at wrong vehicle
speeds when throttle cable is correctly adjusted.
(1) Connect a 100 psi gauge to governor pressure
port. It is located at lower right side of case, below
differential cover (Fig. 2).
(2) Operate transaxle in third gear to read pres-
sures. The governor pressure should respond
smoothly to changes in mph and should return to 0
to 3 psi when vehicle is stopped. High pressure
(above 3 psi) at standstill will prevent the transaxle
from downshifting.
THROTTLE PRESSURE
No gauge port is provided for throttle pressure.
Incorrect throttle pressure should be suspected if
part throttle upshift speeds are either delayed or
occur too early in relation to vehicle speed. Engine
runaway on shifts can also be an indicator of low
throttle pressure setting, or misadjusted throttle
cable.
In no case should throttle pressure be adjusted
until the transaxle throttle cable adjustment has
been verified to be correct.
DIAGNOSIS AND TESTING - TORQUE
CONVERTER HOUSING FLUID LEAKAGE
When diagnosing converter housing fluid leaks,
three actions must be taken before repair:
(1) Verify proper transmission fluid level.
(2) Verify that the leak originates from the con-
verter housing area and is transmission fluid.
(3) Determine the true source of the leak.
Fluid leakage at or around the torque converter
area may originate from an engine oil leak (Fig. 3).
The area should be examined closely. Factory fill
fluid is red and, therefore, can be distinguished from
engine oil.
Some suspected converter housing fluid leaks may
not be leaks at all. They may only be the result of
residual fluid in the converter housing, or excess
fluid spilled during factory fill, or fill after repair.
Converter housing leaks have several potential
sources. Through careful observation, a leak source
can be identified before removing the transmission
for repair.
Pump seal leaks tend to move along the drive hub
and onto the rear of the converter (Fig. 3). Pump
o-ring or pump body leaks follow the same path as a
seal leak. Pump attaching bolt leaks are generally
deposited on the inside of the converter housing and
not on the converter itself. Pump seal or gasket leaksusually travel down the inside of the converter hous-
ing (Fig. 3).
TORQUE CONVERTER LEAKAGE
Possible sources of torque converter leakage are:
²Torque converter weld leaks at the outside diam-
eter weld (Fig. 4).
²Torque converter hub weld (Fig. 4).
Fig. 3 Converter Housing Leak Paths
1 - PUMP SEAL
2 - PUMP VENT
3 - PUMP BOLT
4 - PUMP GASKET
5 - CONVERTER HOUSING
6 - CONVERTER
7 - REAR MAIN SEAL LEAK
Fig. 4 Converter Leak PointsÐTypical
1 - OUTSIDE DIAMETER WELD
2 - TORQUE CONVERTER HUB WELD
3 - STARTER RING GEAR
4 - LUG
21 - 34 AUTOMATIC - 31THRS
AUTOMATIC - 31TH (Continued)

OPERATION
The Brake/Transmission Shift Interlock (BTSI)
Solenoid prevents the transmission shift lever from
being moved out of PARK (P) unless the brake pedal
is applied. The BTSI solenoid is hardwired to and
controlled by the Intelligent Power Module (IPM).
Battery voltage is applied to one side of the solenoid
with the ignition key is in either the ON/RUN or
START positions (Fig. 211). The ground side of the
solenoid is controlled by a driver within the IPM. It
relies on voltage supplied from the stop lamp switch
to the stop lamp sense circuit within the IPM to tell
when the brake pedal is depressed. When the brake
pedal is depressed, the ground circuit opens, de-ener-
gizing the solenoid. When the brake pedal is
released, the ground circuit is closed, energizing the
solenoid.
When the ignition key is in either the ON/RUN or
START positions, the BTSI solenoid is energized, and
the solenoid plunger hook pulls the shift lever pawl
into position, prohibiting the shift lever from moving
out of PARK (P) (Fig. 212). When the brake pedal is
depressed, the ground circuit opens, de-energizing
the solenoid. This moves the gearshift lever pawl out
of the way (Fig. 213), allowing the shift lever to be
moved into any gear position.
Fig. 210 Solenoid Plunger and Return Spring
1 - PLUNGER
2 - RETURN SPRING
3 - BTSI SOLENOID
Fig. 211 Ignition Key/Switch Positions
1 - ACC
2 - LOCK
3 - OFF
4 - ON/RUN
5-START
Fig. 212 Pawl Engaged to Shift Lever
1 - GEAR SHIFT LEVER
2 - GEAR SHIFT LEVER PAWL
21 - 114 AUTOMATIC - 31THRS
SHIFT INTERLOCK SOLENOID (Continued)

OPERATION
The Brake/Transmission Shift Interlock (BTSI)
Solenoid prevents the transmission shift lever from
being moved out of PARK (P) unless the brake pedal
is applied. The BTSI solenoid is hardwired to and
controlled by the Intelligent Power Module (IPM).
Battery voltage is applied to one side of the solenoid
with the ignition key is in either the ON/RUN or
START positions (Fig. 306). The ground side of the
solenoid is controlled by a driver within the IPM. It
relies on voltage supplied from the stop lamp switch
to the stop lamp sense circuit within the IPM to tell
when the brake pedal is depressed. When the brake
pedal is depressed, the ground circuit opens, de-ener-
gizing the solenoid. When the brake pedal is
released, the ground circuit is closed, energizing the
solenoid.
When the ignition key is in either the ON/RUN or
START positions, the BTSI solenoid is energized, and
the solenoid plunger hook pulls the shift lever pawl
into position, prohibiting the shift lever from moving
out of PARK (P) (Fig. 307). When the brake pedal is
depressed, the ground circuit opens, de-energizing
the solenoid. This moves the gearshift lever pawl out
of the way (Fig. 308), allowing the shift lever to be
moved into any gear position.
A conventional mechanical interlock system is also
used. This system manually prohibits shifter move-
ment when the ignition switch is in the LOCK or
ACC positions. Solenoid operation is not required in
these key positions. When the ignition key is in the
OFF position, the gearshift lever is unrestricted, and
able to move into any gear position (during towing,
dead battery, etc.).
Fig. 306 Ignition Key/Switch Positions
1 - ACC
2 - LOCK
3 - OFF
4 - ON/RUN
5-START
Fig. 307 Pawl Engaged to Shift Lever
1 - GEAR SHIFT LEVER
2 - GEAR SHIFT LEVER PAWL
Fig. 308 Pawl Disengaged From Shift Lever
1 - GEAR SHIFT LEVER
2 - GEAR SHIFT LEVER PAWL
RSAUTOMATIC - 41TE21 - 273
SHIFT INTERLOCK SOLENOID (Continued)

DIAGNOSIS AND TESTING - COMMON
PROBLEM CAUSES
The majority of transaxle malfunctions are a result
of:
²Insufficient lubrication
²Incorrect lubricant
²Misassembled or damaged internal components
²Improper operation
HARD SHIFTING
Hard shifting may be caused by a misadjusted
crossover cable. If hard shifting is accompanied by
gear clash, synchronizer clutch and stop rings or gear
teeth may be worn or damaged.
Hard shifting may also be caused by a binding or
broken shift cover mechanism. Remove shift cover
and verify smooth operation. Replace as necessary.
Misassembled synchronizer components also cause
shifting problems. Incorrectly installed synchronizer
sleeves, keys, balls, or springs can cause shift prob-
lems.
NOISY OPERATION
Transaxle noise is most often a result of worn or
damaged components. Chipped, broken gear or syn-
chronizer teeth, and brinnelled, spalled bearings all
cause noise.
Abnormal wear and damage to the internal compo-
nents is frequently the end result of insufficient
lubricant.
SLIPS OUT OF GEAR
Transaxle disengagement may be caused by mis-
aligned or damaged shift components, or worn teeth
on the drive gears or synchronizer components. Incor-
rect assembly also causes gear disengagement. Check
for missing snap rings.
LOW LUBRICANT LEVEL
Insufficient transaxle lubricant is usually the
result of leaks, or inaccurate fluid level check or refill
method. Leakage is evident by the presence of oil
around the leak point. If leakage is not evident, the
condition is probably the result of an underfill.
If air±powered lubrication equipment is used to fill
a transaxle, be sure the equipment is properly cali-
brated. Equipment out of calibration can lead to an
underfill condition.
CLUTCH PROBLEMS
Worn, damaged, or misaligned clutch components
can cause difficult shifting, gear clash, and noise.
A worn or damaged clutch disc, pressure plate, or
release bearing can cause hard shifting and gear
clash.
REMOVAL
REMOVAL - 2.4L GAS
(1) Raise hood.
(2) Disconnect gearshift cables from shift levers/
cover assembly (Fig. 10).
(3) Remove gearshift cable retaining clips from
mounting bracket (Fig. 10). Remove cables and
secure out of way.
(4) Remove three (3) right engine mount bracket-
to-transaxle bolts (Fig. 11).
(5) Raise vehicle on hoist.
(6) Remove front wheel/tires and halfshafts.
(7) Drain transaxle fluid into suitable container.
(8) Remove cradle plate.
(9) Remove front harness retainer and secure har-
ness out of way.
(10) Remove clutch release access cover.
(11)RHD Models:Using Tool 6638A, disconnect
clutch hydraulic circuit quick connect (located on
slave cylinder tube). Remove clutch slave cylinder by
depressing towards case and rotating counter-clock-
wise 60É, while lifting anti-rotation tab out of case
slot with screwdriver (Fig. 12).LHD Models:
Remove clutch release cable by pulling outward on
cable housing, then forward to allow cable core to
pass through case slot (Fig. 13). Disengage T-end
from release lever and secure cable out of way.
(12) Remove engine left mount bracket.
(13) Remove starter motor (Fig. 14).
Fig. 10 Gearshift Cables at Transaxle
1 - SELECTOR CABLE
2 - CABLE RETAINER
3 - CABLE RETAINER
4 - CROSSOVER CABLE
5 - MOUNT BRACKET
RGT850 MANUAL TRANSAXLE21a-11
T850 MANUAL TRANSAXLE (Continued)

When the conditions causing a water leak have
been determined, simulate the conditions as closely
as possible.
²If a leak occurs with the vehicle parked in a
steady light rain, flood the leak area with an open-
ended garden hose.
²If a leak occurs while driving at highway speeds
in a steady rain, test the leak area with a reasonable
velocity stream or fan spray of water. Direct the
spray in a direction comparable to actual conditions.
²If a leak occurs when the vehicle is parked on an
incline, hoist the end or side of the vehicle to simu-
late this condition. This method can be used when
the leak occurs when the vehicle accelerates, stops or
turns. If the leak occurs on acceleration, hoist the
front of the vehicle. If the leak occurs when braking,
hoist the back of the vehicle. If the leak occurs on left
turns, hoist the left side of the vehicle. If the leak
occurs on right turns, hoist the right side of the vehi-
cle. For hoisting recommendations refer to Group 0,
Lubrication and Maintenance, General Information
section.
WATER LEAK DETECTION
To detect a water leak point-of-entry, do a water
test and watch for water tracks or droplets forming
on the inside of the vehicle. If necessary, remove inte-
rior trim covers or panels to gain visual access to the
leak area. If the hose cannot be positioned without
being held, have someone help do the water test.
Some water leaks must be tested for a considerable
length of time to become apparent. When a leak
appears, find the highest point of the water track or
drop. The highest point usually will show the point of
entry. After leak point has been found, repair the
leak and water test to verify that the leak has
stopped.
Locating the entry point of water that is leaking
into a cavity between panels can be difficult. The
trapped water may splash or run from the cavity,
often at a distance from the entry point. Most water
leaks of this type become apparent after accelerating,
stopping, turning, or when on an incline.
MIRROR INSPECTION METHOD
When a leak point area is visually obstructed, use
a suitable mirror to gain visual access. A mirror can
also be used to deflect light to a limited-access area
to assist in locating a leak point.
BRIGHT LIGHT LEAK TEST METHOD
Some water leaks in the luggage compartment can
be detected without water testing. Position the vehi-
cle in a brightly lit area. From inside the darkened
luggage compartment inspect around seals and body
seams. If necessary, have a helper direct a drop lightover the suspected leak areas around the luggage
compartment. If light is visible through a normally
sealed location, water could enter through the open-
ing.
PRESSURIZED LEAK TEST METHOD
When a water leak into the passenger compart-
ment cannot be detected by water testing, pressurize
the passenger compartment and soap test exterior of
the vehicle. To pressurize the passenger compart-
ment, close all doors and windows, start engine, and
set heater control to high blower in HEAT position. If
engine can not be started, connect a charger to the
battery to ensure adequate voltage to the blower.
With interior pressurized, apply dish detergent solu-
tion to suspected leak area on the exterior of the
vehicle. Apply detergent solution with spray device or
soft bristle brush. If soap bubbles occur at a body
seam, joint, seal or gasket, the leak entry point could
be at that location.
DIAGNOSIS AND TESTING - WIND NOISE
Wind noise is the result of most air leaks. Air leaks
can be caused by poor sealing, improper body compo-
nent alignment, body seam porosity, or missing plugs
in the engine compartment or door hinge pillar areas.
All body sealing points should be airtight in normal
driving conditions. Moving sealing surfaces will not
always seal airtight under all conditions. At times,
side glass or door seals will allow wind noise to be
noticed in the passenger compartment during high
cross winds. Over compensating on door or glass
adjustments to stop wind noise that occurs under
severe conditions can cause premature seal wear and
excessive closing or latching effort. After a repair pro-
cedure has been performed, test vehicle to verify
noise has stopped before returning vehicle to use.
Wind noise can also be caused by improperly fitted
exterior moldings or body ornamentation. Loose
moldings can flutter, creating a buzzing or chattering
noise. An open cavity or protruding edge can create a
whistling or howling noise. Inspect the exterior of the
vehicle to verify that these conditions do not exist.
VISUAL INSPECTION BEFORE TESTS
Verify that floor and body plugs are in place and
body components are aligned and sealed. If compo-
nent alignment or sealing is necessary, refer to the
appropriate section of this group for proper proce-
dures.
ROAD TESTING WIND NOISE
(1) Drive the vehicle to verify the general location
of the wind noise.
(2) Apply 50 mm (2 in.) masking tape in 150 mm
(6 in.) lengths along weatherstrips, weld seams or
RSBODY23-3
BODY (Continued)

MANUAL TEMPERATURE CONTROL
The front blower speed must be set to High and
the evaporator temperature sensor must be greater
than 55É F or the test will fail immediately. The test
is activated by depressing the A/C and PWR buttons
simultaneously and holding them depressed for no
less than five seconds. The PWR and A/C LEDs will
blink on and off until the test is complete. If the
LEDs stop blinking after two minutes, then the cool
down test has been completed successfully. If the two
minutes expire without the evaporator temperature
reaching 20É F less than the outside air temperature,
then the cool down test has been failed and further
A/C system diagnosis is required. If the test is failed,
the LEDs will continue to blink across ignition cycles
until the vehicle has been driven for greater than (3
miles).
AUTOMATIC TEMPERATURE CONTROL
The outside air temperature shown in the ATC dis-
play must not be lower than 53É F or the test will not
begin. The ambient air temperature in the room
where the vehicle will be tested must be a minimum
of 21É C (70ÉF) for this test.The test is activated by
depressing the A/C and PWR buttons simultaneously
and holding them depressed for no less than four sec-
onds. The snowflake icon and the DELAY text in the
ATC display will blink on and off alternately until
the test is complete. If the snowflake icon and the
DELAY text stop blinking after two minutes, then
the cool down test has been completed successfully. If
the two minutes expire without the evaporator tem-
perature reaching 20É F less than the evaporator ini-
tial temperature, then the cool down test has been
failed and further A/C system diagnosis is required.
If the test is failed, the snowflake icon and the
DELAY text will continue to blink across ignition
cycles until the vehicle has been driven for greater
than (3 miles).
DIAGNOSIS AND TESTING - A/C
PERFORMANCE TEST
An air conditioning performance test is the best
way to determine whether the system is performing
up to standard. This test also provides valuable clues
as to the possible cause of trouble with the air con-
ditioning system. The ambient air temperature in the
location where the vehicle will be tested must be a
minimum of 21É C (70ÉF) for this test.
WARNING: REFER TO THE APPLICABLE WARN-
INGS AND CAUTIONS FOR THIS SYSTEM BEFORE
PERFORMING THE FOLLOWING OPERATION.(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - WARNING - A/C PLUMBING)
and (Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - CAUTION - A/C PLUMBING).
NOTE: When connecting the service equipment
coupling to the line fitting, verify that the valve of
the coupling is fully closed. This will reduce the
amount of effort required to make the connection.
(1) Connect a tachometer to monitor the engine
speed.
(2) Remove the caps from the refrigerant system
service ports and attach a manifold gauge set to
monitor the refrigerant system pressures.
(3) Set the heater-air conditioner controls so that
the compressor is engaged, the air within the vehicle
is being recirculated, the output air is directed
through the panel outlets, the temperature control is
in the full cool position, and the blower motor is oper-
ating at its highest speed.
(4) Start the engine and allow the engine to oper-
ate for about five minutes or until it reaches normal
operating temperature. Then hold the engine speed
at 1000 rpm with the compressor clutch engaged. If
the compressor clutch does not engage, proceed with
diagnosis of the compressor clutch coil. (Refer to 24 -
HEATING & AIR CONDITIONING/CONTROLS -
FRONT/COMPRESSOR CLUTCH COIL - DIAGNO-
SIS AND TESTING).
(5) Close all the vehicle windows and doors.
(6) Insert a thermometer in the left center panel
outlet and operate the engine for five minutes.
(7) With the compressor clutch engaged, record the
left center panel outlet discharge air temperature,
the discharge pressure (high side service port), and
the suction pressure (low side service port). The com-
pressor clutch may cycle, depending upon the ambi-
ent temperature and humidity. If the clutch cycles,
use the readings obtained before the clutch disen-
gaged.
(8) Compare the discharge air temperature read-
ing to the Performance Temperature and Pressure
chart. If the temperature reading is high, check the
refrigerant system for leaks and proper refrigerant
charge level. (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - FRONT/REFRIGERANT -
DIAGNOSIS AND TESTING - REFRIGERANT SYS-
TEM LEAKS) and (Refer to 24 - HEATING & AIR
CONDITIONING/PLUMBING - FRONT/REFRIGER-
ANT - DIAGNOSIS AND TESTING - REFRIGER-
ANT SYSTEM CHARGE LEVEL).
RSHEATING & AIR CONDITIONING24-5
HEATING & AIR CONDITIONING (Continued)

OPERATION
The compressor is driven by the engine through an
electric clutch, drive pulley and belt arrangement.
The compressor is lubricated by refrigerant oil that is
circulated throughout the refrigerant system with the
refrigerant. The compressor draws in low-pressure
refrigerant vapor from the evaporator through its
suction port. It then compresses the refrigerant into
a high-pressure, high-temperature refrigerant vapor.
The compressor pumps high-pressure refrigerant
vapor to the condenser through the compressor dis-
charge port. The mechanical high pressure relief
valve is designed to vent refrigerant from the system
to protect against damage to the compressor or other
system components, caused by condenser air flow
restrictions or an overcharge of refrigerant. The valve
only vents enough refrigerant to reduce the system
pressure, then re-seats itself. The valve opens at a
discharge pressure of 3445 to 4135 kPA (500 to 600
psi) or above, and closes when a minimum discharge
pressure of 2756 kPa (400 psi) is reached.
DIAGNOSIS AND TESTING - COMPRESSOR
NOISE
Excessive noise while the air conditioning compres-
sor is operating can be caused by loose compressor
mounts, a loose compressor clutch, or high operating
pressures in the refrigerant system. Verify compres-
sor drive belt condition, proper compressor mounting,
correct refrigerant charge level, and compressor head
pressure before compressor repair is performed.
With the close tolerances within the compressor, it
is possible to experience a temporary lockup. The
longer the compressor is inactive, the more likely the
condition is to occur. This condition is the result of
normal refrigerant migration within the refrigerant
system caused by ambient temperature changes. The
refrigerant migration may wash the refrigerant oil
out of the compressor.
NOTE: Prior to a vehicle being removed from ser-
vice or stored for more than two weeks, the com-
pressor should be operated to ensure adequate
refrigerant oil distribution throughout the system
components. Turn on the air conditioner for a min-
imum of five minutes with outside air and the high-
est blower speed selected.
BELT NOISE
If the compressor drive belt slips at initial start-up,
it does not necessarily mean the compressor has
failed. The following procedure can be used to iden-
tify a compressor drive belt noise problem.
²Start the vehicle and run at idle.²Turn the air conditioner On and listen for belt
squeal.
²If belt squeal is heard, turn the air conditioner
Off immediately.
If the belt squeal stops when the air conditioner is
turned Off, perform the following repair procedures.
(1) Using an appropriate sized oil filter wrench or
a strap wrench, grasp the outer diameter of the com-
pressor clutch hub. While facing the compressor,
rotate the hub clockwise, then counterclockwise. If
the hub rotates, proceed to the next step. If the hub
will not rotate, the compressor is internally damaged,
and must be replaced.
(2) Turn the hub clockwise five complete revolu-
tions and remove the tool.
(3) Start the vehicle and run at idle.
(4) Turn the air conditioner On. Observe the com-
pressor and the system for normal operation, noting
cooling performance and noise levels. Operate for five
minutes before turning the air conditioner Off. If
acceptable cooling performance is observed during
compressor operation, the compressor does not need
to be replaced.
(5) Inspect the drive belt for wear, damage, and
proper tension. (Refer to 7 - COOLING/ACCESSORY
DRIVE/DRIVE BELTS - DIAGNOSIS AND TEST-
ING).
REMOVAL - COMPRESSOR
WARNING: REFER TO THE APPLICABLE WARN-
INGS AND CAUTIONS FOR THIS SYSTEM BEFORE
PERFORMING THE FOLLOWING OPERATION.
(Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - WARNING - A/C PLUMBING)
and (Refer to 24 - HEATING & AIR CONDITIONING/
PLUMBING - FRONT - CAUTION - A/C PLUMBING).
(1) Recover the refrigerant from the refrigerant
system. (Refer to 24 - HEATING & AIR CONDI-
TIONING/PLUMBING - FRONT/REFRIGERANT -
STANDARD PROCEDURE - REFRIGERANT
RECOVERY).
(2) Disconnect and isolate the battery negative
cable.
(3) Remove the nut that secures the suction line
fitting to the top of the compressor.
(4) Disconnect the suction line fitting from the
compressor suction port.
(5) Remove the seal from the suction line fitting
and discard.
(6) Install plugs in, or tape over the opened suc-
tion line fitting and the compressor suction port.
(7) Remove the nut that secures the discharge line
fitting to the top of the compressor.
(8) Disconnect the discharge line fitting from the
compressor discharge port.
RSPLUMBING - FRONT24-65
COMPRESSOR (Continued)

LEAK DETECTION PUMP MONITOR
The leak detection assembly incorporates two pri-
mary functions: it must detect a leak in the evapora-
tive system and seal the evaporative system so the
leak detection test can be run.
The primary components within the assembly are:
A three port solenoid that activates both of the func-
tions listed above; a pump which contains a switch,
two check valves and a spring/diaphragm, a canister
vent valve (CVV) seal which contains a spring loaded
vent seal valve.
Immediately after a cold start, between predeter-
mined temperature thresholds limits, the three 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 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 due to the reed switch triggering of
the three port solenoid that prevents the diaphragm
assembly from reaching full travel. After the brief
initialization period, the solenoid is de-energized
allowing atmospheric pressure to enter the pump
cavity, thus permitting the spring to drive the dia-
phragm 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 con-
trolled 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 length.
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 7.5º H20.
The cycle rate of pump strokes is quite rapid as the
system begins to pump up to this pressure. As the
pressure increases, the cycle rate starts to drop off. If
there is no leak in the system, the pump would even-
tually stop pumping at the equalized pressure. If
there is a leak, it will continue to pump at a rate rep-
resentative of the flow characteristic of the size of the
leak. From this information we can determine if the
leak is larger than the required detection limit (cur-
rently set at .020º orifice by CARB). If a leak is
revealed during the leak test portion of the test, the
test is terminated at the end of the test mode and no
further system checks will be performed.
After passing the leak detection phase of the test,
system pressure is maintained by turning on the
LDP's solenoid until the purge system is activated.
Purge activation in effect creates a leak. The cycle
rate is again interrogated and when it increases dueto the flow through the purge system, the leak check
portion of 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.
Evaporative system functionality will be verified by
using the stricter evap purge flow monitor. At an
appropriate warm idle the LDP will be energized to
seal the canister vent. The purge flow will be clocked
up from some small value in an attempt to see a
shift in the 02 control system. If fuel vapor, indicated
by a shift in the 02 control, is present the test is
passed. If not, it is assumed that the purge system is
not functioning in some respect. The LDP is again
turned off and the test is ended.
DESCRIPTION - 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.
OPERATION - SYSTEM
The Powertrain Control Module (PCM) monitors
many different circuits in the fuel injection, ignition,
emission and engine systems. If the PCM senses a
problem with a monitored circuit often enough to
indicate an actual problem, it stores a Diagnostic
Trouble Code (DTC) in the PCM's memory. If the
code applies to a non-emissions related component or
system, and the problem is repaired or ceases to
exist, the PCM cancels the code after 40 warmup
cycles. Diagnostic trouble codes that affect vehicle
emissions illuminate the Malfunction Indicator Lamp
(MIL). Refer to Malfunction Indicator Lamp in this
section.
Certain criteria must be met before the PCM
stores a DTC in memory. The criteria may be a spe-
cific range of engine RPM, engine temperature,
and/or input voltage to the PCM.
The PCM might not store a DTC for a monitored
circuit even though a malfunction has occurred. This
may happen because one of the DTC criteria for the
circuit has not been met.For example, assume the
diagnostic trouble code criteria requires the PCM to
monitor the circuit only when the engine operates
between 750 and 2000 RPM. Suppose the sensor's
output circuit shorts to ground when engine operates
above 2400 RPM (resulting in 0 volt input to the
PCM). Because the condition happens at an engine
25 - 8 EMISSIONS CONTROLRS
EMISSIONS CONTROL (Continued)

ORVR
OPERATION
The emission control principle used in the ORVR sys-
tem is that the fuel flowing into the filler tube (appx. 1º
I.D.) creates an aspiration effect which draws air into
the fill tube (Fig. 6). During refueling, the fuel tank is
vented to the vapor canister to capture escaping vapors.
With air flowing into the filler tube, there are no fuel
vapors escaping to the atmosphere. Once the refueling
vapors are captured by the canister, the vehicle's com-
puter controlled purge system draws vapor out of the
canister for the engine to burn. The vapors flow is
metered by the purge solenoid so that there is no or
minimal impact on driveability or tailpipe emissions.
As fuel starts to flow through the fill tube, it opens
the normally closed check valve and enters the fuel
tank. Vapor or air is expelled from the tank through the
control valve to the vapor canister. Vapor is absorbed in
the canister until vapor flow in the lines stops, either
following shut-off or by having the fuel level in the tank
rise high enough to close the control valve. The controlvalve(Refer to 14 - FUEL SYSTEM/FUEL DELIVERY/
FUEL TANK - OPERATION) contains a float that rises
to seal the large diameter vent path to the canister. At
this point in the fueling of the vehicle, the tank pres-
sure increases, the check valve closes (preventing tank
fuel from spiting back at the operator), and fuel then
rises up the filler tube to shut-off the dispensing nozzle.
If the engine is shut-off while the On-Board diagnos-
tics test is running, low level tank pressure can be
trapped in the fuel tank and fuel can not be added to
the tank until the pressure is relieved. This is due to
the leak detection pump closing the vapor outlet from
the top of the tank and the one-way check valve not
allowing the tank to vent through the fill tube to atmo-
sphere. Therefore, when fuel is added, it will back-up in
the fill tube and shut off the dispensing nozzle. The
pressure can be eliminated in two ways: 1. Vehicle
purge must be activated and for a long enough period to
eliminate the pressure. 2. Removing the fuel cap and
allowing enough time for the system to vent thru the
recirulation tube.
Fig. 6 ORVR System Schematic
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 - CONTROL VALVE
RSEVAPORATIVE EMISSIONS25-15

Major Monitors. If the Task Manager cannot run a
Global Good Trip because a component fault is stop-
ping the monitor from running, it will attempt to
count an Alternate Good Trip.
The Task Manager counts an Alternate Good Trip
for Comprehensive components when the following
conditions are met:
²Two minutes of engine run time
²No other faults occur
The Task Manager counts an Alternate Good Trip
for a Major Monitor when the monitor runs and
passes. Only the Major Monitor that failed needs to
pass to count an Alternate Good Trip.
Warm-Up Cycles
Once the MIL has been extinguished by the Good
Trip Counter, the PCM automatically switches to a
Warm-Up Cycle Counter that can be viewed on the
DRBIIIt. Warm-Up Cycles are used to erase DTCs
and Freeze Frames. Forty Warm-Up cycles must
occur in order for the PCM to self-erase a DTC and
Freeze Frame. A Warm-Up Cycle is defined as fol-
lows:
²Engine coolant temperature must start below
and rise above 160É F
²Engine coolant temperature must rise by 40É F
²No further faults occur
Freeze Frame Data Storage
Once a failure occurs, the Task Manager records
several engine operating conditions and stores it in a
Freeze Frame. The Freeze Frame is considered one
frame of information taken by an on-board data
recorder. When a fault occurs, the PCM stores the
input data from various sensors so that technicians
can determine under what vehicle operating condi-
tions the failure occurred.
The data stored in Freeze Frame is usually
recorded when a system fails the first time for two
trip faults. Freeze Frame data will only be overwrit-
ten by a different fault with a higher priority.
CAUTION: Erasing DTCs, either with the DRBIIIT;or
by disconnecting the battery, also clears all Freeze
Frame data.
Similar Conditions Window
The Similar Conditions Window displays informa-
tion about engine operation during a monitor. Abso-
lute MAP (engine load) and Engine RPM are stored
in this window when a failure occurs. There are two
different Similar conditions Windows: Fuel System
and Misfire.
FUEL SYSTEM
²Fuel System Similar Conditions WindowÐ
An indicator that 'Absolute MAP When Fuel Sys Fail'
and 'RPM When Fuel Sys Failed' are all in the samerange when the failure occurred. Indicated by switch-
ing from 'NO' to 'YES'.
²Absolute MAP When Fuel Sys FailÐ The
stored MAP reading at the time of failure. Informs
the user at what engine load the failure occurred.
²Absolute MAPÐ A live reading of engine load
to aid the user in accessing the Similar Conditions
Window.
²RPM When Fuel Sys FailÐ The stored RPM
reading at the time of failure. Informs the user at
what engine RPM the failure occurred.
²Engine RPMÐ A live reading of engine RPM
to aid the user in accessing the Similar Conditions
Window.
²Adaptive Memory FactorÐ The PCM utilizes
both Short Term Compensation and Long Term Adap-
tive to calculate the Adaptive Memory Factor for
total fuel correction.
²Upstream O2S VoltsÐ A live reading of the
Oxygen Sensor to indicate its performance. For
example, stuck lean, stuck rich, etc.
²SCW Time in Window (Similar Conditions
Window Time in Window)Ð A timer used by the
PCM that indicates that, after all Similar Conditions
have been met, if there has been enough good engine
running time in the SCW without failure detected.
This timer is used to increment a Good Trip.
²Fuel System Good Trip CounterÐATrip
Counter used to turn OFF the MIL for Fuel System
DTCs. To increment a Fuel System Good Trip, the
engine must be in the Similar Conditions Window,
Adaptive Memory Factor must be less than cali-
brated threshold and the Adaptive Memory Factor
must stay below that threshold for a calibrated
amount of time.
²Test Done This TripÐ Indicates that the
monitor has already been run and completed during
the current trip.
MISFIRE
²Same Misfire Warm-Up StateÐ Indicates if
the misfire occurred when the engine was warmed up
(above 160É F).
²In Similar Misfire WindowÐ An indicator
that 'Absolute MAP When Misfire Occurred' and
'RPM When Misfire Occurred' are all in the same
range when the failure occurred. Indicated by switch-
ing from 'NO' to 'YES'.
²Absolute MAP When Misfire OccurredÐ
The stored MAP reading at the time of failure.
Informs the user at what engine load the failure
occurred.
²Absolute MAPÐ A live reading of engine load
to aid the user in accessing the Similar Conditions
Window.
RSON-BOARD DIAGNOSTICS25-25
TASK MANAGER (Continued)