1998 SSANGYONG MUSSO Workshop Repair Manual

5A-64 AUTOMATIC TRANSMISSION
Default Transmission Operating Modes
The TCU relies on accurate information from its inputs and complete control of its outputs to effectively control the
transmission. To ensure that it has both valid inputs and functioning outputs, the TCU carries out both hardware and
software fault detection routines. The TCU will respond to any faults detected by adopting the operating modes which
are detailed below.
The following symptoms of faults are the most obvious results of each fault under ‘normal’ conditions.
There is always the possibility that a fault may not be detected. If undetected fault conditions are present, the
operation of the transmission is difficult to predict.
1 Throttle Fault
lAll shifts will occur as if a nominal throttle (approx. 44%) were applied for shift scheduling.
lAll shifts will be firm as full throttle and hence high engine torque is assumed.
lThe torque converter will be unlocked at all times.
lAll downshifts initiated by the shift lever will occur as though they were ‘automatic’ shifts. That is the engine
braking effect will not occur until near the end of the shift.
lLine pressure will always stay high (solenoid 6 OFF) to cope with assumed high throttle/torque.
If a fault is undetected, the percent throttle is most likely to be interpreted as higher than actual, resulting in late
upshifts, early downshifts, firm shifting and a harsh 3-1 shift when stopping.
2 Throttle Not Learnt Fault
The transmission operates from default throttle calibration values which results in the evaluation of the throttle being
higher (more open) than it is. There(ore at zero throttle settings, the transmission may calculate that sufficient throttle
opening is present to justify high line pressure and switch solenoid 6 to OFF.
Other symptoms are:
a. late upshifts and
b. lock-up maintained at zero throttle when the vehicle speed is sufficiently high.
3 Engine Speed Fault
lAll shifts will be firm because an engine speed corresponding to peak engine torques is assumed.
If a fault is undetected, the engine speed is likely to be interpreted as stalled resulting in soft shifting possibly with an
end of shift bump.
4 Vehicle Speed Sensor Fault
lAll shifts will be controlled by the shift lever with skip downshifts disabled and downshifts only allowed if the
engine speed is low. Fourth gear will be inhibited.
lThe torque converter will be unlocked at all times.
If a fault is undetected, the vehicle is likely to be interpreted as being stationary resulting in first gear operation at all
times. Note that speedometer transducer faults are likely to cause the vehicle’s speedometer to become inoperative.
5 Gear Lever Fault (Inhibitor/PRNDL Switch)
lThe gear lever is assumed to be in the Drive position.
lThe transmission is limited to 2nd,3rd, and R gears only.
lThe rear band will apply at all times when the lever is shifted to P, R or N. (B2 inhibition and reverse lockout
protection is disabled.)
lThe torque converter will be unlocked at all times.
lManually (gear lever) initiated downshifts will not be available.
If a fault is undetected, the gear lever position is likely to be interpreted as being higher than actual. Where Park is the
highest position and Manual 1 is the lowest, the result being the availability of higher gears than selected by the gear
lever.

AUTOMATIC TRANSMISSION 5A-65
If the gear lever is incorrectly adjusted, the transmission may shift gears on bumpy road surfaces.
6 Transmission Oil Temperature Sensing Fault
lAll shifts will be firm until the transmission has warmed up, because a high transmission oil temperature is
assumed.
If a fault is undetected, the temperature is likely to be evaluated as being lower than actual, resulting in softer shifts
with ‘end bump’ (very firm feel at the end of the shift).
7 Mode Setting Fault
lAll shifts will occur as if the mode is set to ‘NORMAL’.
lThe mode indicator will always be off indicating that ‘NORMAL’ mode is selected.
lThe mode indicator will not respond to changes in switch setting.
If a fault is undetected, the mode as indicated by the mode indicator is not likely to respond to the mode switch.
8 Battery Voltage Sensing Fault
If the battery voltage is low then shifts to first gear are inhibited.9 the battery voltage is high (>16.5V) then the
transmission goes into limp home (LHM) mode.
If a fault is undetected, the transmission is likely to incorrectly evaluate an ON/OFF solenoid fault resulting in limp
home mode (LHM) operation.
9 ON/OFF Solenoid Fault (Solenoids 1,2,3 and 4)
The transmission adopts its limp home mode (LHM) operation, described above. However, if solenoid 1 is faulty then
the fourth gear LHM strategy will be adopted independent of vehicle speed.
If a fault is undetected, the operation of the transmission is dependent on which solenoid is actually faulty. The
characteristics for different solenoid fault conditions are listed in table 6.1.2.
10 ON/OFF Solenoid Fault (Solenoids 6,7)
If solenoid 6 is found faulty it is always disabled resulting in high line pressure being applied continuously.
If solenoid 7 is found faulty it is disabled resulting in the transmission being locked always.
The transmission does not go into LHM.
11 Variable Pressure Solenoid Fault
The transmission adopts its LHM operation.
If a fault is undetected, the transmission shift feel is likely to be poor for all shifts.
12 Software Fault
The transmission adopts the third gear LHM strategy of operation, independent of vehicle speed. The operation of
the TCU under this condition is difficult to predict. Its operation may be erratic.
If a fault is undetected, the operation of the TCU is likely to be erratic.
13 Power Supply Fault
The transmission adopts the third gear LHM strategy of operation, independent of vehicle speed. If there is an
intermittent power supply connection, the TCU will power-up in fourth gear and then shift to the appropriate gear to
satisfy the conditions present. The power supply is not monitored for fault evaluation.
All faults except for solenoid faults can be recovered without having to turn the TCU off and back on. However, in
general the recovery requires that no faults are present for a period of time (approx. 3 or 30 seconds). Recovery from
a fault will not clear the fault from the keep alive memory
14 Transmission Sump Temperature Exceeding 135°C
lThe converter lockup clutch will be applied at lower speeds, causing a shudder through the vehicle.
lThe mode indicator will flash in some vehicles.
These faults can be due to the transmission oil overheating or due to an incorrect signal received from the temperature
sensor.

5A-66 AUTOMATIC TRANSMISSION
Diagnostic Trouble Messages
The diagnostic trouble messages generated by the TCU and their possible causes are listed in table 6.1.3.
Table 6.1.2 - Transmission Operations for On/Off Solenoid Faults
Transmission Operation
First gear instead of second and fourth gear instead of third.
This results in a 1®
4 shift as the vehicle accelerates from rest.
Second gear instead of first and third gear instead of fourth.
This results in second gear starts.
Fourth gear instead of first and third gear instead of second.
This results in fourth gear starts.
Second gear instead of third and first gear instead of fourth.
This results in a 1®
2 then 2®
1 (overrun) downshift as the vehicle
accelerates from rest.
The following shifts become poor:
1®
3, 1®
4, 2®
1 2®
3, 2®
4, 4®
2, 4®
1.
The following shifts become poor:
3®
4, 4®
3, 3®
2.
There may be slippage in the gears during torque converter locking.
The following shifts become poor:
1®
2, 1®
3, 1®
4, 2®
3, 2®
4, 3®
1, 3®
2 (All Including Manual), 3®
4,
4®
1,4®
3.
The following shifts become poor:
2®
4, 3®
2.
There may be slippage in the gears during torque converter locking.
Line pressure always high.
Line pressure always low thus resulting in risk of slippage in gears.
Torque converter always unlocked.
Torque converter always locked in 3rd and 4th gears, causing the
vehicle to shudder at lower speeds,Condition
Always ON
Always OFF
Always OFF
Always ON
Always OFF
Always ON
Always OFF
Always ON
Always OFF
Always ON
Always OFF
Always ON
Solenoid
1
2
3
4
6
7

AUTOMATIC TRANSMISSION 5A-67
Table 6.1.3 - Diagnostic Trouble Messages
Description / Cause
There have been no faults recorded since the TCU was last cleared. If
the fault history has never been cleared, then there have been no
faults recorded since the TCU was originally powered up.
There is an internal fault within the TCU.
The voltage measured by the TCU corresponding to the battery sup-
ply voltage has been outside the range of the maximum operating
voltage of 16.5 volts.
The minimum operating voltage depends on the transmission tem-
perature but is typically between 8-9 V for a warm transmission.
The voltage measured by the TCU from the throttle potentiometer has
been outside acceptable levels.
This would typically indicate a loose connection in the wiring to, or
within, the throttle sensor which has caused the signal at the TCU to
read 0V or 5V.
The voltage measured by the TCU across the temperature Input ter-
minals has been outside acceptable levels.
This would typically be caused by a loose connection or short to ground
in the wiring to, or within, the temperature sensor which has caused
the signal at the TCU to read 0V or 5V.
The voltage measured by the TCU across the shift lever input termi-
nals has been outside acceptable levels for a significant length of
time. This would typically be caused by a loose connection or short to
ground in the wiring to, or within, the inhibitor switch which has caused
the signal at the TCU to read 0V or 5V.
The signal from the ignition, of ignition pulses, has either been non-
existent or has been unreliable.
There are two reasons this fault could occur. The first is due to a lack
of ignition pulses when other TCU inputs would indicate that the en-
gine is running, that is the gear lever is in a driving position, the throttle
is applied and vehicle speed increasing.
The second cause of this (aunt is the frequency of the pulses of the
ignition pulse input to the TCU indicate an unachievable engine speed.
The pulses from the shaft speed sensor have either been non-exis-
tent or have been unreliable.
There are three reasons this fault could occur. The first is due to a
sudden loss of speedometer pulses at a time when they were fre quent,
thus indicating an unachievable degree of deceleration of the drive
line. The second cause of this fault is that the frequency of the pulses
on the shaft speed sensor input to the TCU indicate an unachievable
propeller shaft speed. The third is the presence of a high engine speed
in a driving gear with no speedometer pulses. Condition
Test Pass
Transmission Control
Module Fault
Battery Voltage Input
Fault
Throttle Input Fault
Temperature Input Fault
Shift Lever Position
Input Fault
(Inhibitor/PRNDL Switch)
Engine Speed Sensor
Fault
Shaft Speed Sensor
Fault
(Speedo Sensor)Solenoid
1
2
3
4
5
6
7
8

5A-68 AUTOMATIC TRANSMISSION
Description / Cause
The signal from the mode switch is unreliable.
This fault is caused by too many changes in the mode input signal
over a period of time. Typical causes would be an intermittent connec
tion in the switch or wiring or an intermittent short to ground in the
wiring.
The data link between the TCU and the engine management module
is found to be unreliable because the checksum, or the data received,
did not match the correct checksum.
This could be caused by an open circuit, short circuit to ground or a
loose connection in the link wire itself.
Each solenoid in turn is switched off if it was energised, or switched on
if it was not energised by a very small 100 ms pulse. This pulse is too
short for the solenoid to react so transmission operation is not af
fected.
The solenoid feedback voltage is measured before the 100 ms pulse
and again during the pulse. If the difference is outside the acceptable
limits the relevant fault messages are set.
Typical causes would be an open circuit in the wiring to or within the
solenoid, or a short circuit to ground in the wiring to, from or within the
solenoid in question.
If several of these fault codes are presents check the wiring or
connectors that are common to the selected solenoids, especially the
earth connections.
The state of the solenoid feedback voltage is outside acceptable
limits but the faulty solenoid could not be isolated.
The current to solenoid 5 was outside acceptable limits.
This fault results from a mismatch between the current set point for
solenoid 5 and the current measured by the feedback within the TCU.
Typical causes would be an open circuit or short circuit to ground in
the wiring to, from or within the solenoid. It is also possible that there
has been a fault in the solenoid output circuit. If this is the case
however, the fault should be continually present.
The closed throttle position has not been learnt. This fault
may be caused by the transmission not having reached normal
operating temperature or the engine idle speed being incorrect.
The TCU will learn the closed throttle position automatically
when the transmission is brought to normal operating
temperature and the engine is allowed to idle in Drive with the
‘base idle’ correctly set and the air conditioner (if fitted)
switched off. Condition
Mode Switch Input Fault
(Power/Economy Mode)
Data Output Link Fault
On/off Solenoid Fault
(Solenoid 1,2,3,4,6,7)
Solenoid 5 Fault
(Variable Pressure
Solenoid)
Throttle Not LearntSolenoid
9
10
11
12
13

AUTOMATIC TRANSMISSION 5A-69
MECHANICAL TESTS
In Vehicle Transmission Checks
Carry out the following tests before removing the transmission.
lSee Checking Transmission Fluid Level, Section 7.2.1.
lCheck that the transmission oil is not burnt (colour and smell are correct).
lEnsure that the transmission is not in limp home mode (LHM).
lCheck that the battery terminals and the earth connections are not corroded or loose.
lCheck the engine stall speed is within the handbook value.
lCheck that the cooler flow is not restricted.
lCheck that all electrical plug connections are tight.
lCarry out a road test to confirm the symptoms, if necessary.
lInspect the oil, ensure that there are no metal or other contaminants in the oil pan.
Diagnosing Oil Leaks
Determine the source of oil leaks by firstly cleaning down the affected area, then driving the vehicle.
Inspect the seals to confirm the source of the leak.
lTo determine the source of a rear servo oil leak, raise the vehicle on a hoist, then carry out a reverse stall.
lTo determine the source of a front servo leak, raise the vehicle on a hoist, then run the vehicle in second gear.
Troubleshooting Charts
The troubleshooting charts are set out as follows:
lTable 6.2.1 Drive Faults,
lTable 6.2.2 Faulty Shift Patterns.
lTable 6.2.3 Shift Quality Faults.
lTable 6.2.4 After Teardown Faults.
Table 6.2.1 - Drive Faults
Action
Check the fluid level. Top up as necessary.
Inspect and clean C1/C2 feed.
Reinstall/renew the ‘z’ link.
Remove, clean and re-install the PRV.
Inspect and replace as necessary.
Inspect and replace as necessary.
Inspect and replace as necessary.
Check servo adjustment or replace rear band
as necessary.
Check for failure in C3, C3 hub or C1/C2 cylin-
der. Repair as necessary.
Inspect and clean PRV.
Inspect and replace pump gears as necessary.
Inspect and repair as necessary. Possible Cause
Insufficient auto transmission fluid.
Blocked feed in C1/C2 cylinder.
‘Z’ link displaced.
Primal regulator valve (PRV) jammed open.
Overdrive shaft or input shaft seal rings
failed.
3-4 or 1-2 one way clutch (OWC) installed
backwards or failed.
C2 piston broken or cracked.
Rear band or servo faulty.
Failure in C3, C3 hub or C1/C2 cylinder.
Jammed primary regulator valve (PRV).
Damaged/broken pump gears.
Dislodged output shaft snap ring.Symptom
No Drive in D
No Drive in
Reverse
No engine braking
in Manual 1
Engine braking in
Manual 1 is OK
No drive in Drive
and Reverse

5A-70 AUTOMATIC TRANSMISSION
Action
Inspect S1. Repair or replace as necessary.
Check for 12 Volts applied to S1 at all times or
for wiring fault.
Inspect S1. Repair or replace as necessary.
Check for 12 Volts applied to S1 at all times or
for wiring fault.
Inspect S2. Repair or replace as necessary.
Check for open circuit or wiring fault.
Inspect S2. Repair or replace as necessary.
Check for open circuit or wiring fault.
Inspect and adjust as necessary.
Inspect and repair as necessary.
Inspect and replace or refit as necessary.
Inspect ‘O’ ring. Refit or replace as necessary.
Inspect the 2-3 shift valve. Repair or replace
as necessary.
Inspect C1 clutch. Repair or replace as neces-
sary.
Inspect ball. Refit or replace as necessary.
Inspect C4. Repair C4 or replace C4 wave plate
as necessary.
Inspect rear band adjustment. Adjust as nec-
essary.
Inspect ball- Refit or replace as necessary.
Inspect’0’ring. Refit or replace as necessary.
Inspect C4 and C4 wave plate. Repair or re-
place as necessary.
Inspect inhibitor switch.
Repair or replace as necessary.
Inspect the 1-2 shift valve.
Repair or replace as necessary
Inspect inhibitor switch.
Repair or replace as necessary.
Inspect the 2-3 shift valve.
Repair or replace as necessary. Possible Cause
S1 always OFF.
S1 always ON.
S2 always OFF.
S2 always ON.
B1 failed.
Loose band adjustment.
Front servo piston or seal failed.
S1/S2 ball misplaced,
Smaller’0’ring on front servo piston failed
or missing.
2-3 shift valve jammed.
C1 clutch failed or slipping in 3rd and 4th.
(Gives 1st in 3rd and 2nd in 4th.)
Over-run clutch (OC)/low ball misplaced.
C4 failed or C4 wave plate broken.
Rear band slipping when hot.
Reverse/Low-1st ball misplaced.
Rear servo inner ‘O’ ring missing.
C4 failed or C4 wave plate broken.
Inhibitor switch faulty.
1-2 shift valve jammed.
Inhibitor switch fault, 1-2 only.
2-3 shift valve jammed.Symptom
2-3 shift only
(no 4th or 1st)
1-4 shift only
1-3-4 (Delayed
1-2shift)
4-3 shift only
1-2-Neutral
(1st over run)
1-3 shift only
1-3-4 only
1-2-1 only
No manual 4-3,3-2
or 2-1
No manual 1st
1st gear only or
2nd,3rd, and 4th
only
1st and 2nd only
or 1st, 3rd and 4th
only

AUTOMATIC TRANSMISSION 5A-71
Table 6.2.2 - Faulty Shift Patterns
Action
Inspect inhibitor switch. Repair or replace as
necessary.
Inspect the 3-4 shift valve. Repair or replace
as necessary.
Inspect the release valve. Repair or replace as
necessary.
Inspect S3 or S2. Repair or replace as neces-
sary.
Inspect the regulator valve. Repair or replace
as necessary.
Inspect the ball. Refit or replace as necessary.
Inspect the sealing rings. Refit or replace as
necessary.
Inspect the ‘O’ rings. Refit or replace as neces-
sary.
Inspect the bleed ball. Refit or replace as nec-
essary.
Inspect S1 or S4. Repair or replace as neces-
sary.
Inspect the release valve. Repair or replace as
necessary.
Inspect the band. Adjust as necessary.
Inspect the ‘O’ rings. Refit or replace as neces-
sary.
Inspect S5. Repair or replace as necessary.
Inspect the regulator valve. Repair or replace
as necessary. Possible Cause
Inhibitor switch fault, 1-2-3 only.
3-4 shift valve jammed.
Jammed band 1 release valve.
Faulty S3 or S2 solenoid.
Faulty clutch apply regulator valve.
Missing or damaged clutch apply feed ball.
Damaged input shaft sealing rings.
Damaged C1 piston ‘O’ rings.
Damaged or dislodged C1 piston bleed
ball.
Faulty S1 or S4 solenoid.
Jammed band 1 release valve.
Incorrect front band adjustment.
Damaged front servo piston ‘O’ rings.
Faulty or damaged variable pressure
solenoid (S5).
Faulty band apply regulator valve.Symptom
1st,2nd and 4th
only or 1st,2nd,
and 3rd (tied up in
3rd)
Harsh 2-3 shift
Harsh 3-4 shift