JAGUAR X308 1998 2.G Workshop Manual

Automatic Transmission/Transaxle - 4.0L NA V8 - AJ27/3.2L NA V8 - AJ26
- Transmission Descriptio
n
Description an
d Operation
Transmission As

sembly
Int
roduction

Compon
ent Descriptions
The t

orque converter:
Acts as a fluid

coupling between the
engine and transmission geartrain.
P
rovides multiplication of engine torque.
Cons

ists of an impeller, turbine and stat
or, housed within a converter cover.
Has a l
ock-up clutch with variable slip control.
The transmission casing:
Houses the geartrain and elec t
ro-hydraulic control unit.
Contains

the input speed sensor which measures turbine speed.
Contai

ns the output speed sensor which measures the transmission output speed.
It
em
Par
t Number
De
scription
1—Torque c

onverter housing
2—Tran

smission casing
3—Fluid pan


4—Transmission bre

ather
5—Re

ar extension housing
6—16

-way connector
7—Gear s

elector shaft

Contains th
e hydraulic system pump.
Contains
th
e fluid temperature sensor.
The epicyclic geartrain:
Provi des fi
ve forward gears and Reverse.
Has
h
ydraulically actuated, multi-disk clutches, to select the required gear ratios.
Feature

s clutch-to-clutch operation to permit
gear shifts for uninterrupted power flow.
The electro-hydraulic control unit:
Is lo c
ated in the lower part of
the unit, within the fluid pan.
Is controlled
by the TCM (transmissio
n control module), and the manual selector valve which is cable operated.
Re
gulates the flow of fluid to the ge
artrain clutches via three solenoid-operated valv es and the manual selector
valve.
Has fi ve pressure
regulators for controll
ing fluid pressures within the system.
Is con
nected to the TCM via a 16-way connector mounted on
the left-hand side of the transmission casing. Refer to
Connector Pins Identification, Section 307-01A.
The hydraulic system pump:
Is l o
cated at the front of the transmission casing.
Is dri
v
en from the impeller hub,
pressurising the fluid whenever the engine is running.
Supplie
s fluid under pressure to the torq
ue converter, geartrain, electro-hydr aulic control unit and the lubrication
circuit.
D r
aws fluid from the fluid pa
n below the transmission casing, through a filter.
The rear extension housing:
Is bolt
ed to the rear of the transmission casing.
Provides the rear engine / transmi

ssion mo
unting point; refer to section 303-01.
Carrie
s the transmission output shaft oil seal.
Filled-for-l
i
fe Fluid System
The
transm
ission is 'filled for life' and
does not require fluid changes, except where extreme driving conditions prevail.
Routine level checking is not required and a dipstick is not pr ovided. A level / filler plug is fitted for level checking and
replenishment, following service actions; see 303-01 General Procedures.
Transmission Torque Converter

Op
eration
The T
ransmission Control Module (TCM) is
able to monitor the state of the torque converter clut ch at all times.
There are three operating modes for the converter
1. 1. Fully open - Torque converter 'unlocked'
2. 2. Fully closed - Torque converter 'locked'
3. 3. Slip control - The TCM monitors slip and may apply sufficie nt pressure to allow a small degree of slip. This mode
maximises economy by reducing slip to a minimum whilst providing isolation from drive-line shunt and vibration.
The TCM constantly measures the slip within the torque conver ter by comparing engine speed (via CAN) and input (turbine
speed). Differences in these speeds indicate the amount of slip.
Clutch Hydraulic Pressure Regulation
The T
CM supplies an internally switched +1
2V supply to the #4 pressure regulator. The regulator is operated by switching
the other side of the operating winding to ground. Hydraulic pressure is controlled by 'pulse width modulation' (PWM) of the
ground switching signal i.e. the duty cycle; the time that the pressure regulator is switched on.
Hydraulic Control
- Transmission Pre
ssure Regulators an d Shift Solenoids

Opera
tion
F
l
uid flow within the transmission assembly is controlled
by three solenoid valves and five pressure regulators.
The TCM supplies an internally switched +12V supply to each sh ift solenoid and pressure regulator. Hydraulic pressure from
the pressure regulators is controlled by 'pulse width modulation' (PWM) of the ground switching signal i.e. the duty cycle;
the time that the pressure regu lator is switched on. Control of the solenoids is effected by switching one side to ground
through the TCM.
During normal operation the TCM monitors 'Switch On' of the so lenoids, regulators and the TCM output stages, but does not
check output stage 'Switch Off'.
It e
m
Par
t
Number
De
scr
iption
1—Shif
t Sole
noid #3
2—Shif
t Sole
noid #2
3—Shif
t Sole
noid #1
4—Pressure R
e
gulator #5
5—Pressure R
e
gulator #4
6—Pressure R
e
gulator #3
7—Pressure R
e
gulator #2
8—Pressure R
e
gulator #1

Voltage is monitored at the regulators and solenoids for continuity and shorts. For example, when a solenoid is ON the
voltage on the TCM side should be ground , when OFF the voltage should be +12.
Shift Solenoid

The function of the three soleno id valves is to control the flow of transmissi on oil to the various transmission components.
Three solenoid valves are located wi thin the transmission assembly, and are closed when not energized.
Pressure Regulator

The function of the five pressu re regulators is to modulate the oil pressure to the various transmission components. The
regulators are pulse width modulated by the TCM, switching to ground potential. The other side of the regulators being
connected, via an internal TCM relay, to battery voltage. The regulator is closed when not energized by the TCM.
Transmission Fluid Temperature Sensor

Operation
The transmission fluid temperature sensor is integrated into the internal harness within the fluid pan.
It should be noted that this component is not serviceable, ne cessitating the renewal of the internal harness should a fault
occur.
Following engine start-up, if the fluid temperature is < 20 °C and does not increase by 10 °C after 180 seconds, a failure
judgement is made. A similar judgement is made should the temperature change by more than 5 °C in <100 milliseconds.
The MIL is illuminated if the failure judgement is made on two successive trips.
Sensor output is continuously monitored for out of range values. If a sustained high, or low inpu t is sensed, indicating a
harness or connector fault, a failure judgement is made.
Location of Sensor Within The Harness

Temperature / Resistance Relationship Chart

Transmission Speed Sensors (Gear Shift Control)

Operation
There are two speed sensors within the transmission assembly; one on the input shaft or convertor turbine and the other on the output shaft.
Both sensors are of the inductive type and sense toothed wheels; the input wheel having 30 teeth and the output 36 teeth.

Temperature ( °C)Nominal Resistance (kOHM)
-20685
0812
20953
401107
601276
801458
1001653

Input speed is monitored by the TCM with a rationality check being made against output speed. A fault will be flagged if the
indicated input speed exceeds 7400 rpm. Additionally, a failure judgement will be made if the indicated input speed is <160
rpm with engine speed >608 rpm and output speed >224 rpm
The procedure is similar for the output sp eed diagnostic. A fault (non OBDII) will be flagged if the indicated input speed
exceeds 6712 rpm. Additionally a failure judgement will be ma de if the indicated output speed is <160 rpm and the average
road wheel speed exceeds 100 rpm.
Under normal circumstance s after the output speed diagnost ic fault code has been set, the TCM uses rear wheel speed
information to compute its calculations, this has no effect on transmission operation. However, should a second fault occur,
in the ABS system, thus making rear wheel speed information unavailable, an additional fault code will be logged.
Control Systems
Introduction
Gear selection is achieved by controlling the flow of transmission fluid to internal multi-disc clutches.
The three solenoid valves direct the transmission fluid flow to the selected clutches and the pressure regulators control the
fluid pressure to each component. One pr essure regulator serves as a master pressure control for the entire system and a
second is used exclusively for torque converter clutch lock-up operation.
The TCM controls the internal components thus determining gear selection and shift pattern.
In the event of an electronic system fault the basic function s Park, Reverse Neutral and Drive Fourth are retained by the
hydraulic system.
Transmission Control Module (TCM)

The TCM is located in the same housing as th e ECM and is accessed in the same manner.
The TCM performs several 'self check' procedur es to ensure correct operation. It is possible due to the nature of these faults
that the module will fail to communicate with other nodes. However, condemnation of the TCM should not take place until
any CAN or power supply related problems have been resolved.
There are three self check procedures for the TCM. 1. 1. Check on ROM by calculatin
g a checksum and comparing this with a known stored value.

2.2. Check on non-volatile diagnostic memory by wr iting a test pattern and then reading it back.
3. 3. Internal 'watchdog' hardware to check whether the TCM has crashed.
Transmission Control Module Supply Voltage
The TCM monitors battery and igni tion switched supply voltages.
A permanent supply is used to maintain a battery backed 'memor y'. Should this supply be cut, due to battery disconnection
perhaps, the 'adaptive shift' valu es will be lost. This will result in a small reduction in shift quality for a period until th e
adaptions are 're-learned'
The TCM will adopt 'limp home' mode as a result of the supply voltage being >16V or <7V with an engine speed >1600
rpm.
Should the ignition supply be >7V but <9V the TCM will hold the gear that it has currently selected. If after 2.5 seconds,
with the engine speed >1600 rpm, the voltage remains at this level, 'limp home' mode will be adopted. The 2.5 second
delay is built in to prevent reaction to a momentary voltage fluctuation.
Operation
CAUTION: Disconnection of the TCM and / or the vehicle batt ery will cause system adaptions to be lost; this may be
apparent by shift quality degradation. Fo llowing reconnection, a period of 'varied' driving will reinstate adaptions and thus
normal operation. Please ensure that the customer is made aware that the adaption period is variable and may occur after
handover, as the transmission re-learns the prevailing driving style.
• NOTE: Should the TCM fail, please ensure that the control housing cooling fan is operating correctly. Failure of the cooling
fan MUST be rectified before renewing the TCM and details of a fan fa ilure should accompany the returned TCM.
The TCM processes information received in both analogue and digital form, such as:
Transmission input speed Transmission output speed Throttle position Pedal demand Gear selector position Engine torque Engine speed Transmission oil temperature Mode switch
This information is then used by the TC M to control shift energy management and decide which shift program to implement
and which gear to select.
The TCM uses the various sensors and inpu ts to monitor the correct operation of the system an d is programmed to take
default action and inform the operator when a fault occurs.
Safety Functions
The safety functions are designed to safeguard against inappr opriate actions by the operator as well as against system
malfunctions. The system prevents reve rse gear from being engaged at high forward speeds and prevents manual
downshifting at excessive engine speeds; these functions are not operational in mechanical limp-home mode.
The TCM constantly monitors the transmissi on for faults. In the event of a problem the TCM will adopt a 'limp home' mode
in which only P R N D - (selector in D but only fourth gear is enabled) are available. The operator will be made aware of
certain faults by an in strument panel warning.
The electrical and diagnostic system has been designed such that system integrity is protected at all times, the safety
concept being based on th e following three points:

1.1. The hydraulic system has 'fail-safe' characteristics regardin g its electrical operation, such that should the power
supply be lost to the electro-hydraulic actuators the transmission will initiate a limp-home mode.
2. 2. Recognition of critical shift operation by monitoring the last element in the signal path, ie the solenoid valve, and
checking by means of redundant me asured variables, ie engine speed, input speed and output speed.
3. 3. Each time the vehicle is started there is a check on the entire safety hardware and the associated program parts
and signal paths. A malfunction in this part of the system, or triggering of the safety circuit, is communicated to
the operator through the illumination of the transmission warning lamp.
TCM Inputs
Input Speed Sensor (Torque Converter Turbine)
The input speed sensor provides the TCM with transmission inpu t shaft speed information. This signal is produced from an
inductive pick-up, generating 30 pulses per revolution.
Transmission Output Speed Sensor
The output speed sensor provides the TCM with transmission ou tput shaft speed information. This signal is produced from
an inductive pick-up, generati ng 36 pulses per revolution.
Transmission Oil Temperature Sensor
A thermistor which provides an electrical indication of the oi l temperature to the TCM. The signal is measured as a voltage
with reference to analog ue ground in the TCM.
Kickdown Switch (where fitted)
Kickdown is intended to provide maximum vehicle acceleration , via the appropriate downshift(s), when the operator uses
full throttle. A kickdown switch provides an electrical signal to the TCM wh en the accelerator pedal is fully pressed. The
switch is normally open, connected to vehicle ground. Should the switch fail the TCM will detect kickdown using the
accelerator pedal position.
Throttle Pedal Stop (where fitted)
This component, used where the kickdown switch is not fitted, limits throttle pedal travel .in the same way. The kickdown
feature is retained, but is controlled by throttle position only. The pedal stop must be set, using the PDU, in the same way
as the kickdown switch to optimize performance.
Mode Selection Switch
The mode selection switch is a two position switch indicati ng to the TCM the current performance mode selected by the
driver. The switch generates a tw o-bit digital input to the TCM.
Rotary Position Switch
The rotary position switch detects the position of the transmis sion selector shaft. The switch is supplied as part of a new
transmission assembly, mounted on the transmission body. The swit ch is used to indicate to the TCM the six positions of the shaft: Park, Reverse, Neutral, Drive, Third and Second. The switch provides a four-bit input to the TCM.
Drive to Fourth Switch
Detects the movement of the selector lever from Drive to Fourth position. The selector cable, and therefore the transmission selector shaft, does not move as the lever is operated between these two positions. The switch is located within the 'J-gate'
assembly, producing a digital output to indicate to the TCM that the lever has moved from D to 4 .
Serial Communications Interfaces