key CHRYSLER VOYAGER 1996 Service Manual

the current draw will drop to approximately 9±12
amps per plug.
Total momentary current draw for all four plugs is
approximately 100 amps on a cold engine dropping to
a total of approximately 40 amps after the plugs are
heated.
Electrical operation of the glow plugs are con-
trolled by the glow plug relay. Refer to the previous
Glow Plug RelayÐPCM Output for additional infor-
mation.
EXHAUST GAS RECIRCULATION (EGR)
SOLENOIDÐPCM OUTPUT
This circuit controls operation of the Exhaust Gas
Recirculation (EGR) solenoid. The EGR solenoid (Fig.
11) controls operation of the EGR valve.
Refer to Group 25, Emission Control System for
information. See EGR solenoid.
DIAGNOSIS AND TESTING
DIESEL DIAGONSTICS
The PCM controller does engine off diagonstics
tests, which may be heard for about 60 seconds after
turning the key off.
DIESEL PCM RELAY TEST
To perform a test of the relay and its related cir-
cuitry, refer to the DRB scan tool. To test the relay
only, refer to RelaysÐOperation/Testing in this sec-
tion of the group.
Diagnostic Trouble Codes:Refer to On-Board
Diagnostics in Group 25, Emission Control System
for a list of Diagnostic Trouble Codes (DTC's) for cer-
tain fuel system components.
ENGINE SPEED SENSOR TEST
To perform a test of the engine speed sensor and
its related circuitry, refer to the DRB scan tool.
Diagnostic Trouble Codes:Refer to On-Board
Diagnostics in Group 25, Emission Control System
for a list of Diagnostic Trouble Codes (DTC's) for cer-
tain fuel system components.
ENGINE COOLANT TEMPERATURE SENSOR TEST
The sensor is located on the side of cylinder head
near the rear of fuel injection pump (Fig. 13).
For a list of Diagnostic Trouble Codes (DTC's) for
certain fuel system components, refer to On-Board
Diagnostics in Group 25, Emission Control System.
To test the sensor only, refer to the following:
(1) Disconnect wire harness connector from coolant
temperature sensor.
(2) Test the resistance of the sensor with a high
input impedance (digital) volt±ohmmeter. The resis-
tance (as measured across the sensor terminals)should be less than 1340 ohms with the engine
warm. Refer to the following Sensor Resistance
(OHMS) chart. Replace the sensor if it is not within
the range of resistance specified in the chart.
(3) Test continuity of the wire harness. Do this
between the PCM wire harness connector and the
sensor connector terminal. Also test continuity of
wire harness to the sensor connector terminal. Refer
Fig. 13 Engine Coolant Temperature Sensor
Location
SENSOR RESISTANCE (OHMS)
14 - 50 FUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINENS/GS
DESCRIPTION AND OPERATION (Continued)

to Group 8W for wiring connector and circuitry infor-
mation. Repair the wire harness if an open circuit is
indicated.
(4) After tests are completed, connect electrical
connector to sensor.
GLOW PLUG TEST
Hard starting or a rough idle after starting may be
caused by one or more defective glow plugs. Before
testing the glow plugs, a test of the glow plug relay
should be performed. This will ensure that 12V+ is
available at the plugs when starting the engine.
Refer to the Glow Plug Relay Test for information.
For accurate test results, the glow plugs should be
removed from the engine. The plugs must be checked
when cold.Do not check the plugs if the engine
has recently been operated. If plugs are
checked when warm, incorrect amp gauge
readings will result.
Use Churchill Glow Plug Tester DX.900 or an
equivalent (Fig. 14) for the following tests. This
tester is equipped with 4 timer lamps.
(1) Remove the glow plugs from the engine. Refer
to Glow Plug Removal/Installation.
(2) Attach the red lead of the tester to the 12V+
(positive) side of the battery.
(3) Attach the black lead of the tester to the 12V±
(negative) side of the battery.
(4) Fit the glow plug into the top of the tester and
secure it with the spring loaded bar (Fig. 14).
(5) Attach the third lead wire of the tester to the
electrical terminal at the end of the glow plug.(6) When performing the test, the tester button
(Fig. 14) should be held continuously without release
for 20 seconds as indicated by the 4 timer lamps.
Each illuminated lamp represents a 5 second time
lapse.
(a) Press and hold the tester button (Fig. 14)
and note the amp gauge reading. The gauge read-
ing should indicate a momentary, initial current
draw (surge) of approximately 25 amps. After the
initial surge, the amp gauge reading should begin
to fall off. The glow plug tip should start to glow
an orange color after 5 seconds. If the tip did not
glow after 5 seconds, replace the glow plug. Before
discarding the glow plug, check the position of the
circuit breaker on the bottom of the plug tester. It
may have to be reset. Reset if necessary.
(b) Continue to hold the tester button while
observing the amp gauge and the 4 timer lamps.
When all 4 lamps are illuminated, indicating a 20
second time lapse, the amp gauge reading should
indicate a 9±12 amp current draw. If not, replace
the glow plug. Refer to Glow Plug Removal/Instal-
lation.
(7) Check each glow plug in this manner using one
20 second cycle. If the glow plug is to be retested, it
must first be allowed to cool to room temperature.
WARNING: THE GLOW PLUG WILL BECOME
EXTREMELY HOT (GLOWING) DURING THESE
TESTS. BURNS COULD RESULT IF IMPROPERLY
HANDLED. ALLOW THE GLOW PLUG TO COOL
BEFORE REMOVING FROM TESTER.
(8) Remove the glow plug from the tester.
GLOW PLUG RELAY TEST
The glow plug relay is located in the engine com-
partment on the left±inner fender (Fig. 15).
When the ignition (key) switch is placed in the ON
position, a signal is sent to the PCM relating current
engine coolant temperature. This signal is sent from
the engine coolant temperature sensor.
After receiving this signal, the PCM will deter-
mine if, when and for how long a period the glow
plug relay should be activated. This is done before,
during and after the engine is started. Whenever the
glow plug relay is activated, it will control the 12V+
100 amp circuit for the operation of the four glow
plugs.
The Glow Plug lamp is tied to this circuit. Lamp
operation is also controlled by the PCM.
With a cold engine, the glow plug relay and glow
plugs may be activated for a maximum time of 200
seconds. Refer to the Glow Plug Control chart for a
temperature/time comparison of glow plug relay oper-
ation.
Fig. 14 Typical Glow Plug Tester
NS/GSFUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINE 14 - 51
DIAGNOSIS AND TESTING (Continued)

In this chart, Pre±Heat and Post±Heat times are
mentioned. Pre±heat is the amount of time the glow
plug relay circuit is activated when the ignition (key)
switch is ON, but the engine has yet to be started.
Post±heat is the amount of time the glow plug relay
circuit is activated after the engine is operating. The
Glow Plug lamp will not be illuminated during the
post±heat cycle.
TESTING:
Disconnect and isolate the electrical connectors
(Fig. 16) at all four glow plugs. With the engine cool
or cold, and the key in the ON position, check for
10±12 volts + at each electrical connector. 10±12 volts
+ should be at each connector whenever the PCM is
operating in the pre±heat or post±heat cycles (refer
to the following Glow Plug Control chart).Be very
careful not to allow any of the four discon-
nected glow plug electrical connectors to con-
tact a metal surface. When the key is turned to
the ON position, approximately 100 amps at 12
volts is supplied to these connectors.If 10±12
volts + is not available at each connector, check con-
tinuity of wiring harness directly to the relay. If con-
tinuity is good directly to the relay, the fault is either
with the relay or the relay input from the PCM. To
test the relay only, refer to RelaysÐOperation/Test-
ing in this section of the group. If the relay test is
good, refer to the DRB scan tool.
Diagnostic Trouble Codes:Refer to On-Board
Diagnostics in Group 25, Emission Control System
for a list of Diagnostic Trouble Codes (DTC's) for cer-
tain fuel system components.
RELAYSÐOPERATION/TESTING
The following description of operation and
tests apply only to the Diesel PCM and other
relays. The terminals on the bottom of each relay
are numbered (Fig. 17).
OPERATION
²Terminal number 30 is connected to battery volt-
age. For both the Diesel and other relays, terminal
30 is connected to battery voltage at all times.
²The PCM grounds the coil side of the relay
through terminal number 85.
²Terminal number 86 supplies voltage to the coil
side of the relay.
²When the PCM de-energizes the Diesel PCM
and other relays, terminal number 87A connects to
terminal 30. This is the Off position. In the off posi-
tion, voltage is not supplied to the rest of the circuit.
Terminal 87A is the center terminal on the relay.
Fig. 15 Glow Plug Relay Location
Fig. 16 Wiring Connection at Glow Plug
GLOW PLUG CONTROL
14 - 52 FUEL SYSTEMÐ2.5L DIESEL ENGINE/2.0L GAS ENGINENS/GS
DIAGNOSIS AND TESTING (Continued)

(1) Remove cap from power steering fluid reser-
voir.
(2) Using a siphon pump, remove as much power
steering fluid as possible from the power steering
fluid reservoir.
(3) With the ignition key in the locked position
turn the steering wheel to the left until the steering
wheel is in the locked position.
(4) With the vehicle on the ground, disconnect the
steering column shaft coupler from the steering gear
intermediate coupler (Fig. 3).
(5) Raise vehicle on jack stands or centered on a
frame contact type hoist. See Hoisting in the Lubri-
cation and Maintenance section of this service man-
ual, for the required lifting procedure to be used for
this vehicle.
(6) Remove the front tires.
(7) Raise the heat sleeve (Fig. 4) on the power
steering return hose to expose the return hose to
steel tube connection. Remove the return hose from
the metal tube of the power steering fluid return line
(Fig. 4). Then allow the remaining power steering
fluid to drain from the system through the hose and
metal tube.
(8) Remove nut attaching outer tie rod end to
steering knuckle (Fig. 5).Nut is to be removed
from tie rod end using the following procedure,
hold tie rod end stud with a 11/32 socket while
loosening and removing nut with wrench.
(9) Remove both tie rod ends from steering knuck-
les, using Puller Special Tool MB-990635 or
MB-991113 (Fig. 6).
Fig. 3 Steering Column Shaft To Intermediate Shaft
Attachment
Fig. 4 Power Steering Fluid Return Hose
Connection
Fig. 5 Removing/Installing Tie Rod End Attaching
Nut
Fig. 6 Tie Rod End Removal From Steering Knuckle
19 - 28 STEERINGNS
REMOVAL AND INSTALLATION (Continued)

STEERING COLUMN
INDEX
page page
DESCRIPTION AND OPERATION
STEERING COLUMN DESCRIPTION......... 36
DIAGNOSIS AND TESTING
STEERING COLUMN..................... 38
SERVICE PROCEDURES
STEERING COLUMN SERVICE PROCEDURE
WARNINGS........................... 38REMOVAL AND INSTALLATION
STEERING COLUMN ASSEMBLY............ 38
SPECIFICATIONS
STEERING COLUMN FASTENER TORQUE
SPECIFICATIONS...................... 45
DESCRIPTION AND OPERATION
STEERING COLUMN DESCRIPTION
The steering column (Fig. 1) has been designed to
be serviced only as a complete assembly, if a compo-
nent of the steering column is defective. The only
replaceable components of the steering columnassembly are the key cylinder, ignition switch, multi-
function switch, clockspring, halo lamp, speed control
switches, driver airbag, trim shrouds and steering
wheel. These replaceable components of the steering
column can be serviced without requiring removal of
the steering column from the vehicle.
Fig. 1 Steering Column Assembly Components
19 - 36 STEERINGNS

DIAGNOSIS AND TESTING
STEERING COLUMN
For diagnosis of conditions relating to the steering
column, refer to the steering system diagnosis charts,
in the diagnosis and testing section at the beginning
of this group.
SERVICE PROCEDURES
STEERING COLUMN SERVICE PROCEDURE
WARNINGS
WARNING: BEFORE BEGINNING ANY SERVICE
PROCEDURES THAT INVOLVES REMOVING THE
AIR BAG. REMOVE AND ISOLATE THE NEGATIVE
(-) BATTERY CABLE (GROUND) FROM THE VEHI-
CLE BATTERY. THIS IS THE ONLY SURE WAY TO
DISABLE THE AIR BAG SYSTEM. FAILURE TO DO
THIS COULD RESULT IN ACCIDENTAL AIR BAG
DEPLOYMENT AND POSSIBLE PERSONAL INJURY.
WARNING: THE AIR BAG SYSTEM IS A SENSITIVE,
COMPLEX ELECTRO-MECHANICAL UNIT. BEFORE
ATTEMPTING TO DIAGNOSE, REMOVE OR INSTALL
THE AIR BAG SYSTEM COMPONENTS YOU MUST
FIRST DISCONNECT AND ISOLATE THE BATTERY
NEGATIVE (GROUND) CABLE. FAILURE TO DO SO
COULD RESULT IN ACCIDENTAL DEPLOYMENT OF
THE AIR BAG AND POSSIBLE PERSONAL INJURY.
THE FASTENERS, SCREWS, AND BOLTS, ORIGI-
NALLY USED FOR THE AIR BAG COMPONENTS,
HAVE SPECIAL COATINGS AND ARE SPECIFI-
CALLY DESIGNED FOR THE AIR BAG SYSTEM.
THEY MUST NEVER BE REPLACED WITH ANY SUB-
STITUTES. ANYTIME A NEW FASTENER IS
NEEDED, REPLACE WITH THE CORRECT FASTEN-
ERS PROVIDED IN THE SERVICE PACKAGE OR
FASTENERS LISTED IN THE PARTS BOOKS.
BEFORE SERVICING A STEERING COLUMN
EQUIPPED WITH AN AIR BAG, REFER TO GROUP
8M, ELECTRICAL FOR PROPER AND SAFE SER-
VICE PROCEDURES.
NOTE: Safety goggles should be worn at all times
when working on steering columns.
CAUTION: Disconnect negative (ground) cable
from the battery, before servicing any column com-
ponent.CAUTION: Do not attempt to remove the pivot pins
to disassemble the tilting mechanism. Damage will
occur.
REMOVAL AND INSTALLATION
STEERING COLUMN ASSEMBLY
To service the steering wheel and its components
or the air bag, refer to Group 8M, Restraint Systems.
Follow all WARNINGS.
To service the switches, refer to the appropriate
section of Group 8, Electrical.
To replace the steering column assembly, refer to
the steering column removal procedure.
REMOVE
(1) Make sure the front wheels of the vehicle are
in thestraight aheadposition before beginning the
column removal procedure.
(2) Disconnect negative (ground) cable from the
battery and isolate cable from battery terminal.
(3) Remove the screws attaching the lower steer-
ing column cover to the instrument panel (Fig. 2).
Remove the lower trim panel from the lower instru-
ment panel.
(4) Remove the park brake pedal release cable
from the park brake release lever (Fig. 3).
(5) Remove the 10 bolts attaching the steering col-
umn cover liner (Fig. 4) to the instrument panel.
Remove the steering column cover liner from the
lower instrument panel.
(6) Rotate key cylinder to the lock position and
remove key. Rotate the steering wheel a half turn to
the left until the steering column lock engages keep-
ing the steering column in the locked position (Fig.
5).
Fig. 2 Lower Steering Column Cover Attachment
Locations
19 - 38 STEERINGNS

CAUTION: When installing steering wheel puller
bolts in steering wheel, (Fig. 8) do not thread bolt
into steering wheel more than a half inch. If bolts
are threaded into the steering wheel more than a
half inch they will contact and damage the clock-
spring.
(11) Remove the steering wheel from steering col-
umn shaft using Puller, Special Tool, Snap-On
CJ2001JP or an equivalent (Fig. 8).
CAUTION: The upper and lower steering column
shrouds are held together using retaining clips.
When separating and removing the shrouds from
the steering column be careful not to break the
retaining clips off the shrouds
(12) Remove the 3 screws (Fig. 9) attaching the
upper and lower shrouds to the steering column.
Then remove the upper and lower shrouds (Fig. 9)
from the steering column.(13) Remove the vehicle wiring harness connectors
(Fig. 10) from the clock spring assembly.
CAUTION: Do not rotate the clock spring after it is
removed from the multifunction switch.
(14) Remove the clock spring from the multi-func-
tion switch.
(15) Remove the vehicle wiring harness connector
from the top of the multi-function switch (Fig. 11).
(16) Remove the screw (Fig. 12) attaching the
multi-function switch housing to the tilt head of the
steering column assembly.
(17) Remove the multi-function switch (Fig. 12)
from the tilt head of the steering column assembly.
(18) Remove the vehicle wiring harness connector
from the key cylinder halo light (Fig. 13).
(19) Remove the 3 wiring harness connectors from
the ignition switch (Fig. 14).
Fig. 8 Removing Steering Wheel From Steering
Column Shaft
Fig. 9 Steering Column Shrouds
Fig. 10 Wiring Harness Connections To Clock
Spring
Fig. 11 Wiring Harness Connection To Multi-
Function Switch
19 - 40 STEERINGNS
REMOVAL AND INSTALLATION (Continued)

(28) Remove steering column assembly from vehi-
cle. Use care to avoid damage to paint or interior
trim.
INSTALL
(1) Ensure the plastic mounting capsules (Fig. 22)
are installed in the upper mounting bracket of the
steering column. Mounting capsules must be
installed as shown in (Fig. 22) with the thicker edge
of the capsule facing the top of the steering column.
(2) Install steering column assembly into its open-
ing in instrument panel. Install the steering column
lower bracket so the bracket is squarely installed on
its mounting studs (Fig. 21). Then align and install
steering column upper bracket on its mounting studs
(Fig. 21). Tighten the 4 steering column assembly
mounting nut/washer assemblies to a torque of 12
N´m (105 in. lbs.).
(3) Assemble the steering column shaft coupler
(Fig. 20) onto the steering gear intermediate coupler.
Install steering column coupler to intermediate shaft
retaining pinch bolt (Fig. 20). Tighten the pinch bolt
nut to a torque of 28 N´m (250 in. lbs.). Install safety
pin (Fig. 20) in steering column shaft coupler pinch
bolt.
(4) Install the gear slector cable and its mounting
bracket on the upper mounting bracket of the steer-
ing column (Fig. 17). Install and securely tighten the
mounting bracket attaching bolt.
(5) Install the gear selector cable on the pin of the
gear shifter (Fig. 16).
(6) If the vehicle is equipped with a 3 speed non-
electronic transmission, install the PRNDL actuating
cable on the gear shifter pin after the gear selector
cable is installing (Fig. 15).
(7) If the vehicle is equipped with a 3 speed non-
electronic transmission, install the attaching clip
(Fig. 15) for the PRNDL actuating cable on the steer-ing column/shift cable bracket. Cable guide tube will
bow toward passenger side of vehicle. Verify that
actuating cable is operating correctly, then slip the
loop on the end of the cable over end of pin on shift
lever and install in groove (Fig. 15).
(8) Install the steering column fixed shroud on the
steering column assembly (Fig. 19). Shroud is
mounted to steering column using 2 attaching screws
accessed from top of fixed shroud.
(9) Install the instrument cluster trim bezel (Fig.
18) on the instrument panel. The trim bezel is
mounted to the instrument panel using 2 attaching
screws (Fig. 18) and retaining clips.
(10) Install the 3 wiring harness connectors on the
ignition switch (Fig. 14).
(11) Install the vehicle wiring harness connector
into the key cylinder halo light (Fig. 13).
(12) Install the multi-function switch (Fig. 12) on
the tilt head of the steering column assembly. Then
install screw (Fig. 12) attaching multi-function
switch to tilt head of steering column.
(13) Install the vehicle wiring harness connector
on the multi-function switch (Fig. 11). Be sure latch
on connector is fully engaged with tab on switch.
(14) Install the clock spring on the multi-function
switch.
(15) Install the vehicle wiring harness connector
(Fig. 10) on the clock spring assembly.
(16) Install the lower steering column shroud on
the tilt head of the steering column (Fig. 23). Install
and securely tighten the screw attaching the lower
shroud to the tilt head.
(17) Install the upper steering column shroud on
the tilt head of the steering column (Fig. 24). Install
and securely tighten the 2 screws attaching the
upper shroud to the lower shroud.
Fig. 22 Mounting Capsules Correctly Installed On
Steering Column
Fig. 23 Lower Steering Column Shroud Installed
NSSTEERING 19 - 43
REMOVAL AND INSTALLATION (Continued)

Inspect all valve springs for distortion and col-
lapsed coils. Inspect all valves and plugs for burrs,
nicks, and scores. Small nicks and scores may be
removed with crocus cloth, providing extreme care is
taken not to round off sharp edges. The sharpness of
these edges is vitally important. It prevents foreign
matter from lodging between valve and valve body.
This reduces the possibility of sticking. Inspect all
valves and plugs for freedom of operation in valve
body bores.
When bores, valves, and plugs are clean and dry,
the valves and plugs should fall freely in the bores.
The valve body bores do not change its dimensions
with use. Therefore, a valve body that was function-
ing properly when vehicle was new, will operate cor-
rectly if it is properly and thoroughly cleaned. There
is no need to replace valve body unless it is damaged
in handling.
ADJUSTMENTS
GEARSHIFT CABLE ADJUSTMENT
Lift and rotate the gearshift hand lever into the
park (P) gate position and remove the ignition key.
This confirms the shift lever is in the gated park (P)
position.
After confirming the park gate position, turn the
ignition switch. If the starter will operate, the park
gate position is correct. Move the shift lever into the
neutral (N) position. If the starter will operate in this
position, the linkage is properly adjusted. If the
starter fails to operate in either position, linkage
adjustment is required.
(1) Park the vehicle on level ground and set the
parking brake.
(2) Place the gearshift lever in park (P) gate posi-
tion and remove key.
(3) Loosen the cable adjustment screw at the tran-
saxle operating lever (Fig. 160).
(4) Pull the transaxle operating lever fully forward
to the park detent position.
(5) Release the park brake, then rock the vehicle
to assure it is in park lock. Reset the park brake.
(6) Tighten the cable adjustment screw to 8 N´m
(70 in. lbs.). Gearshift cable should now be properly
adjusted.
(7) Verify PRNDL indicator still displays the corre-
sponding gear completely. If not, readjustment of
PRNDL may be required.
(8) Check adjustment by using the preceding pro-
cedure.
THROTTLE PRESSURE LINKAGE ADJUSTMENT
The throttle pressure rod adjustment is very
important to proper transaxle operation. This adjust-
ment positions a valve which controls shift speed,shift quality, and part throttle downshift sensitivity.
If the setting is too short, early shifts and slippage
between shifts may occur. If the setting is too long,
shifts may be delayed and part throttle downshifts
may be very sensitive.
With engine at operating temperature, adjust idle
speed of engine using a tachometer. Refer to Group
14, Fuel System for idle speed Specifications and
adjustment.
ROD ADJUSTMENT PROCEDURE
(1) Perform transaxle throttle pressure adjustment
while engine is at normal operating temperature.
(2) Loosen adjustment swivel lock screw.
(3) To insure proper adjustment, swivel must be
free to slide along flat end of throttle rod. Disassem-
ble and clean or repair parts to assure free action, if
necessary.
(4) Hold transaxle throttle lever firmly toward
engine, against its internal stop. Tighten swivel lock
screw to 11 N´m (100 in. lbs.)
(5) The adjustment is finished and linkage back-
lash was automatically removed by the preload
spring.
(6) I
f lubrication is required see Group 0, Lubrica-
tion.
BAND ADJUSTMENT
KICKDOWN BAND (FRONT)
The kickdown band adjusting screw is located on
left side (top front) of the transaxle case.
(1) Loosen locknut and back off nut approximately
five turns. Test adjusting screw for free turning in
the transaxle case.
(2) Using wrench, tighten adjusting screw to 8
N´m (72 in. lbs.).
Fig. 160 Gearshift Cable Adjustment
NSTRANSAXLE AND POWER TRANSFER UNIT 21 - 51
CLEANING AND INSPECTION (Continued)

CAUTION: Some clutch packs appear similar, but
they are not the same. Do not interchange clutch
components, as they might fail.
HYDRAULICS
The hydraulics of the transaxle provide:
²Manual shift lever select function
²Main line pressure regulation
²Torque converter and cooler flow control
Oil flow to the friction elements is controlled
directly by four solenoid valves. The hydraulics also
include a unique logic- controlled solenoid torque con-
verter clutch control valve. This valve locks out the
1st gear reaction element with the application of 2nd,
direct, or overdrive gear elements. It also redirects
the 1st gear solenoid output so that it can control
torque converter clutch operation. To regain access to
1st gear, a sequence of commands must be used to
move the solenoid TCC control valve. This precludes
any application of the 1st gear reaction element with
other elements applied. It also allows one solenoid to
control two friction elements.
Small, high-rate accumulators are provided in each
controlled friction element circuit. These serve to
absorb the pressure responses, and allow the controls
to read and respond to changes that are occurring.
SOLENOIDS
The solenoid valves perform most control functions,
these valves must be extremely durable and tolerant
of dirt. For that reason hardened-steel poppet and
ball valves are used. These are free from any close
operating clearances. The solenoids operate the
valves directly without any intermediate element.
Direct operation means that these units must have
very high output. They must close against the size-
able flow areas and high line pressures. Fast
response is also required to meet the control require-
ments.
Two of the solenoids are normally-venting and two
are normally-applying; this was done to provide a
default mode of operation. With no electrical power,
the transmission provides 2nd gear in (OD), (3), or
(L) shift lever positions. All other transmission lever
positions will operate normally. The choice of 2nd
gear was made to provide adequate breakaway per-
formance while still accommodating highway speeds.
SENSORS
There are three pressure switches to identify sole-
noid application. There are two speed sensors to read
input (torque converter turbine) and output (parking
sprag) speeds. There is also a transmission range
sensor to indicate the manual shift lever position.
The pressure switches are incorporated in an assem-
bly with the solenoids. Engine speed, throttle posi-tion, temperature, etc., are also observed. Some of
these signals are read directly from the engine con-
trol sensors; others are read from a multiplex circuit
with the powertrain control module.
ELECTRONICS
The 41TE Transmission Control Module (TCM) is
located underhood in a potted, die-cast aluminum
housing. The module used is a new controller called
EATX III. The TCM has a sealed, 60-way connector.
ADAPTIVE CONTROLS
These controls function by reading the input and
output speeds over 140 times a second and respond-
ing to each new reading. This provides the precise
and sophisticated friction element control needed to
make smooth clutch-to-clutch shifts for all gear
changes. The use of overrunning clutches or other
shift quality aids are not required. As with most
automatic transaxles, all shifts involve releasing one
element and applying a different element. In simpli-
fied terms, the upshift logic allows the releasing ele-
ment to slip backwards slightly. This ensures that it
does not have excess capacity. The apply element is
filled until it begins to make the speed change to the
higher gear. The apply pressure is then controlled to
maintain the desired rate of speed change. This con-
tinues until the shift is made. The key to providing
excellent shift quality is precision. For example, the
release element for upshifts is allowed to slip back-
wards slightly. The amount of that slip is typically
less than a total of 20 degrees. To achieve that pre-
cision, the TCM learns the traits of the transaxle
that it is controlling. It learns the release rate of the
releasing element and the apply time of the applying
element. It also learns the rate at which the apply
element builds pressure sufficient to begin making
the speed change. This method achieves more preci-
sion than would be possible with exacting tolerances.
It can also adapt to any changes that occur with age
or environment.
For kickdown shifts, the control logic allows the
releasing element to slip. Then controls the rate at
which the input (and engine) accelerate. When the
lower gear speed is achieved, the releasing element
reapplies to maintain that speed until the apply ele-
ment is filled. This provides quick response since the
engine begins to accelerate immediately. This also
provides a smooth torque exchange since the release
element can control the rate of torque increase. This
control can make any powertrain feel more respon-
sive without increasing harshness.
Adaptive controls respond to input speed changes.
They compensate for changes in engine or friction
element torque and provide good, consistent shift
quality for the life of the transaxle.
NSTRANSAXLE AND POWER TRANSFER UNIT 21 - 73
DESCRIPTION AND OPERATION (Continued)