SSANGYONG MUSSO 2003 Service Manual

5A-22 AUTOMATIC TRANSMISSIONCONTROL SYSTEMS
GENERAL
There are two control systems associated with the transmission. The electronic control system monitors vehicle
parameters and adjusts the transmission performance. The hydraulic control system implements the electronic controlsystem commands. ELECTRONIC CONTROL SYSTEM
The electronic control system is comprised of sensors, a TCU and seven solenoids. The TCU reads the inputs, and
under software control activates the outputs according to values stored in read only memory (ROM).
The TCU controls the hydraulic control system. This control is via the hydraulic valve body, which contains seven
electro-magnetic solenoids. Six of the seven solenoids are used to control the line pressure, operate the shift valves
and the torque converter lock-up clutch, and to turn on and off the two regulator valves (The two regulator valvescontrol the shift feel.).
The seventh solenoid is the proportional or variable pressure solenoid (VPS) which works with the two regulator
valves to control shift feel.
Figure 3.1 details a typical TCU control system schematic.
The individual component locations, operation and specifications which make up the electronic control subsystem are covered in this section.
Figure 3.1 - Typical TCU Control System Schematic

AUTOMATIC TRANSMISSION 5A-23
Temperature (°°
°°
° C)
-20 020100 135 (Overheat Mode Threshold)
Maximum
17,287 6,616 2,72319685Minimum
13,638 5,1772,278177 75 Resistance (Ohms)
Table 3.1 - Temperature / Resistance Characteristics
Figure 3.2 - Temperature / Resistance Characteristics

5A-24 AUTOMATIC TRANSMISSION
Transmission Control Unit(TCU)
The TCU is an in-vehicle micro-processor based transmission management system. It is usually mounted in the
vehicle cabin, under the instrument panel, under the seat, behind the side kick panels or under the floor in the
footwell on the passenger side. Different control units are supplied for different vehicle applications.The TCU contains:
Processing logic circuits which include a central microcontroller and a back-up memory system.
Input circuits.
Output circuits which control external devices such as the variable pressure solenoid (VPS), on/off solenoid
drivers, a diagnostics output and the driving mode indicator light.
The various items which make up the TCU are discussed below.
Processing Logic
Shift schedule and calibration information is stored in an erasable programmable read only memory (EEPROM).
Throttle input calibration constants and the diagnostics information are stored in electrically erasable programmable
read only memory (EEPROM) that retains the memory even when power to the TCU is disconnected. In operation the software continuously monitors the input values and uses these, via the shift schedule, to determine the required gear state, At the same time it monitors, via the solenoid outputs, the current gear state. Whenever the
input conditions change such that the required gear state is different to the current gear state, the TCU initiates a
gear shift to bring the two states back into line.
Once the TCU has determined the type of gear shift required the software accesses the shift logic, estimates the
engine torque output, adjusts the variable pressure solenoid ramp pressure then executes the shift.
The TCU continuously monitors every input and output circuit for short or open circuits and operating range. When
a failure or abnormal operation is detected the TCU records the condition code in the diagnostics memory and
implements a limp mode, The actual limp mode used depends upon the failure detected with the object to maintain
maximum driveability without damaging the transmission. In general input failures are handled by providing a default
value. Output failures, which are capable of damaging the transmission, result in full limp mode giving only third or
fourth gear and reverse. For further details of limp modes and memory retention refer to the Diagnostic Section.
The TCU is designed to operate at ambient temperatures between -40 and 85°C . It is also protected against
electrical noise and voltage spikes, however all the usual precautions should be observed, for example when arc welding or jump starting. TCU Inputs
To function correctly, the TCU requires engine speed, road speed, transmission sump temperature, throttle position
and gear position inputs to determine the variable pressure solenoid current ramp and on/off solenoid states. This
ensures the correct gear selection and shift feel for all driving conditions. The inputs required by the TCU are as follows: Engine Speed
The engine speed signal is derived from the tachometer signal line, a dedicated sensor or a Controlled Area Network (CAN).
Road Speed
4WD (Diesel) - The shaft speed signal is derived from the speedo sensor located on the transfer case. This signal is transmitted directly to the TCU.
4WD (Gasoline) - The speedo sensor sends the shaft speed signal to the engine control module (ECM). The
information is then transferred to the TCU via the CAN.
Transmission Sump Temperature
The transmission sump temperature sensor is a thermistor located in the solenoid wiring loom within the transmission.
This sensor is a typical NTC resistor with low temperatures producing a high resistance and high temperatures

AUTOMATIC TRANSMISSION 5A-25
producing a low resistance.
Temperature/Resistance characteristics and location within the solenoid wiring loom are given in tables 3-1 and 3- 2, and figures 3.2 and 3.3.
If the transmission sump temperature exceeds 135°C, the TCU will impose converter lock-up at lower vehicle
speeds and in some vehicles flashes the mode indicator lamp. This results in maximum oil flow through the
external oil cooler and eliminates slippage in the torque converter. Both these actions combine to reduce the oil
temperature in the transmission.
Connects To
Solenoid 1 Solenoid 2Solenoid 3Solenoid 4Solenoid 5 Solenoid 6 Solenoid 7Solenoid 5
Temp Sensor
Temp SensorWire Color Red
Blue
Yellow
Orange GreenViolet
Brown
Green White WhitePin No.
1 2345 6 789
10
Table 3.2 - Pin No. Codes for Temperature Sensor Location In Solenoid Loom
Figure 3.3 - Temperature Sensor Location in Solenoid Loom

5A-26 AUTOMATIC TRANSMISSIONInhibitor Switch
Throttle Position SensorThe throttle position sensor(TPS) is a resistance potentiometer mounted on the throttle body of the engine.
It transmits a signal to the TCU proportional to the throttle plate opening. The potentiometer is connected to the TCU by three wires:
5 volts positive supply, earth and variable wiper voltage.Throttle voltage adjustments are as follows:
Closed throttle voltage is 0.2V to 1.0V.
Wide open throttle voltage is 3V -4.7V.
These measurements are taken between pins 29 and 27 of the TCU.
Maintaining good shift feel through the transmission life span is dependant on having an accurate measure of
the engine throttle position. To achieve this the TCU
continuously monitors the maximum and minimum throttle
potentiometer voltages and, if a change occurs, stores the new voltage values.
However these limits will be lost and will require relearning
should a new TCU be installed, or the throttle calibration data
is cleared by the execution of a particular sequence, This last
instance depends on the installation, and reference should be
made to the Diagnostics Section of this manual. The relearningwill happen automatically Notice
Above figure of T.P.S. is for the diesel enginewhich is installed on the injection pump.
Gear Position Sensor
The gear position sensor is incorporated in the inhibitor switch mounted on the side of the transmission case.
(Refer to figure 3.5.) The gear position sensor is a multi-function switch providing three functions: Inhibit starting of the vehicle when the shift lever is in aposition other than Park or Neutral
Illuminate the reversing lamps when Reverse is
selected indicate to the TCU which lever position has been selected by way of a varying resistance (Refer to
table 3.3.)
Figure 3.5 - Inhibitor Switch

AUTOMATIC TRANSMISSION 5A-27
Shift Lever Position
Manual 1 Manual 2Manual 3Drive Netural ReverseParkResistance (OHMS) 1k - 1.4k
1.8k - 2.2k
3k - 3.4k
4.5k - 4.9k 6.8k - 7.2k
10.8k - 11.2k 18.6k - 19k
Table 3.3 - Readings for Resistance/Shift Lever Positions Diagnostics Inputs
The diagnostics control input or K-line is used to initiate the outputting of diagnostics data from the TCU to a diagnostic
test instrument. This input may also be used to clear the stored fault history data from the TCU’s
retentive memory. Connection to the diagnostics input of the TCU is via a connector included in the vehicle’s wiring
harness or computer interface. Refer to the vehicle manufacturer’ s manual for the location of the self test connectors.
Battery Voltage Monitoring Input
The battery voltage monitoring input connects to the positive side of the battery. The signal is taken from the main supply to the TCU.
If operating conditions are such that the battery voltage at the TCU falls below 11.3V the transmission will adopt a ‘low
voltage’ mode of operating in which shifts into first gear are inhibited. All other shifts are allowed but may not occur
because of the reduced voltage. This condition normally occurs only when the battery is in poor condition.
When system voltage recovers, the TCU will resume normal operation after a 3 second delay period. TCU Outputs
The outputs from the TCU are supplied to the components described below: Solenoids
The TCU controls seven solenoids. Solenoids 1 to 6 (S1 to S6) are mounted in the valve body, while Solenoid 7 (S7)
is mounted in the pump cover. The normal state (OPEN/CLOSED) and the functions associated with the solenoids
are detailed in table 3.4. Table 3.5 details the S1 and S2 logic for static gear states. The logic during gear changes for
S1 to S4 and S7 is detailed in table 3.6.

5A-28 AUTOMATIC TRANSMISSION
Table 3.4 - Solenoid States and Functions
Table 3.5 - Solenoid Logic for Static Gear States
Solenoids 1 and 2 Solenoids 3 and 4 Solenoid 5 Solenoid 6 Solenoid 7S1 and S2 are normally open On/off solenoids that set the selected gear.
These solenoids determine static gear position by operating the shift valves.
Refer to table 3.5. Note that S1 and S2 solenoids also send signal pres- sure to allow or prohibit rear band engagement.
S3 and S4 are normally open On/off solenoids that combine to control
shift quality and sequencing. S3 switches the clutch regulator valve off oron. S4 switches the front band regulator valve off or on. S5 is a variable force solenoid that ramps the pressure during gear changes. This solenoid provides the signal pressure to the clutch and
band regulator, thereby controlling the shift pressures.
S6 is a normally open On/off solenoid that sets the high/low level of linepressure, Solenoid off gives high pressure.
S7 is a normally open On/off solenoid that controls the application of the converter clutch. Solenoid on activates the clutch.
S2
ON ON
OFFOFFOFF OFF OFFS1
ON
OFF OFF ON
OFF OFF OFF
Gear
1st
2nd 3rd
4th
Reverse Neutral Park

AUTOMATIC TRANSMISSION 5A-29
Table 3.6- Solenoid Operation During Gearshifts
To Initiate Shift
S1 OFF S4 ONS1 OFF S2 OFF S3 ONS4 ONS2 OFF
S3 ON S4 ON S2 OFFS3 ONS4 ONS1 ON S4 ON S4 ON S3 ON S3 ON S4 ON S2 ON S4 ON S3 ON S4 ON S4 ON S7 ON To Complete Shift
S4 OFF S3 OFF S4 OFF S3 OFF S4 OFF S3 OFF S4 OFF S4 OFF S1 OFF S4 OFFS1 OFFS2 ON S3 OFF S2 ONS3 OFFS4 OFFS4 OFF S1 ON S2 ONS3 OFF S4 OFF S1 ONS4 OFF S7 OFFTypical S5 Current Ramp
750mA to 600mA 850mA to 750mA 850mA to 750mA 700mA to 500mA 750mA to 600mA 750mA to 900mA 750mA to 950mA 600mA to 1000mA 600mA to 450mA @ 20 kph. 550mA to 400mA @ 60 kph. 800mA to 650mA @ 100 kph. 700mA to 950mA 800mA to 950mA 700mA to 400mA 600mA to 100mA
Shift
1-2 1-3 1-4 2-3 3-4 4-3 4-2 4-1 3-2 3-1 2-1
Conv. Clutch ON OFF

5A-30 AUTOMATIC TRANSMISSION
Solenoid Valve Symbols (On/off Solenoids)
The solenoid symbol shown adjacent to each solenoid on the
hydraulic system schematics indicates the state of the oil flow
through the solenoid valve with the power On or 0ff. Refer to
figure 3.6 for the On/off operational details of NO solenoidvalves. Normally Open (NO) Solenoid POWER ON
Line 500 port is closed. The output port is open to exhaust at the solenoid valve. POWER OFF
The exhaust port is closed. The output port is open to line 500,Figure 3.6- Normally Open (NO) Symbols
Variable Pressure Solenoid Multiplexing System
Friction element shifting pressures are controlled by the variable pressure solenoid (VPS).
Line pressure is completely independent of shift pressure and is a function of throttle position, gear state and enginespeed.
S5 is a proportional or variable pressure solenoid that provides the signal pressure to the clutch and band regulator
valves thereby controlling shift pressures.
VPS pressure is multiplexed to the clutch regulator valve, the band regulator valve and the converter clutch regulator
valve during automatic gearshifts.
A variable pressure solenoid produces a hydraulic pressure inversely proportional to the current applied. During a
gearshift the TCU applies a progressively increasing or decreasing (ramped) current to the solenoid. Current applied will vary between a minimum of 200 mA and a maximum of 1000 mA, Increasing current decreases output (55)
pressure. Decreasing current increases output (55) pressure.
Line 500 pressure, (approximately 440 to 560 kPa), is the reference pressure for the VPS, and the VPS outputpressure is always below line 500 pressure.
When the VPS is at standby, that is no gearshift is taking place, the VPS current is set to 200 mA giving maximum output pressure.
Under steady state conditions the band and clutch regulator valve solenoids are switched off. This applies full Line
500 pressure to the plunger and because Line 500 pressure is always greater than S5 pressure it squeezes the S5
oil out between the regulator valve and the plunger. The friction elements are then fed oil pressure equal to Line 500multiplied by the amplification ratio.
When a shift is initiated the required On/off solenoid is switched on cutting the supply of Line 500 to the plunger.
At the same time the VPS pressure is reduced to the ramp start value and assumes control of the regulator valve by
pushing the plunger away from the valve. The VPS then carries out the required pressure ramp and the timed shift is
completed by switching Off the On/off solenoid and returning the VPS to the standby pressure.
This system enables either the band or clutch or both to be electrically controlled for each gearshift. Mode Indicator Light
Depending on the application, the mode indicator light may be used to indicate the mode that has been selected or
if an overheat condition exists. The mode indicator light is usually located on the instrument cluster. Communication Systems CAN
The controller area network (CAN) connects various control modules by using a twisted pair of wires, to share
common information. This results in a reduction of sensors and wiring. Typical applications include using the engine
controller to obtain the actual engine speed and throttle position, and adding these to the network. The ABS controller
(if fitted) can be used to obtain the road speed signal. This information is then available to the TCU without anyadditional sensors.

AUTOMATIC TRANSMISSION 5A-31
K-Line
The K-line is typically used for obtaining diagnostic information from the TCU. A computer with a special interface is
connected to the TCU and all current faults, stored faults, runtime parameters are then available. The stored faultcodes can also be cleared.
The K-line can be used for vehicle coding at the manufacturer’ s plant or in the workshop. This allows for one TCU
design to be used over different vehicle models. The particular code is sent to the microprocessor via the K line and
this results in the software selecting the correct shift and VPS ramp parameters. HYDRAULIC CONTROL SYSTEM
The hydraulic controls are located in the valve body, pump body and main case.The valve body contains the following:
Manual valve,
Three shift valves,
Sequence valve,
solenoid supply pressure regulator valve,
line pressure control valve,
clutch apply regulator valve,
band apply regulator valve,
S1 to S6, and
Reverse lockout valve.
The pump body contains the following:
Primary regulator valve for line pressure,
converter clutch regulator valve,
converter clutch control valve,
S7,and
C1 bias valve.
The main case contains the following:
B1R exhaust valve
The hydraulic control system schematic is shown at figure 3.7.
All upshifts are accomplished by simultaneously switching on a shift valve(s), switching VPS pressure to the band
and/or clutch regulator valve, and then sending the VPS a ramped current. The shift is completed by switching the
regulators off and at the same time causing the VPS to reach maximum . pressure. All downshifts are accomplished
by switching VPS pressure to the band and/or clutch regulator valve and sending a ramped current to the VPS. The
shift is completed by simultaneously switching the regulators off, switching the shift valves and at the same timecausing the VPS to return to stand-by pressure.
The primary regulator valve is located in the pump cover and supplies four line pressures; high and low for forward
gears, and high and low for reverse. This pressure has no effect on shift quality and merely provides static clutch
capacity during steady state operation. Low pressure can be obtained by activating an On/off solenoid with high line pressure being the default mode.
Torque converter lock-up is initiated by toggling the converter clutch control valve with an On/off solenoid. The actual apply and release of the clutch is regulated by the VPS via the converter clutch regulator valve. As an additionalsafety feature, the lock-up is hydraulically disabled in first and second gear by the bias valve which only supplies oilto the lock-up solenoid when C1 is applied in third and fourth gears. This prevents the vehicle from being renderedimmobile in the unlikely event of S7 becoming stuck.
The solenoid supply valve provides reference pressure for all the solenoids.