Scania Opticruise Troubleshooting
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Issue 1
Opticruise
Description of operation and work description
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Contents
General Opticruise in brief ..............................................3
Introduction ........................................................4
Controls and operation .......................................6
Fault codes
Description of operation
Gear changing ....................................................7
Opticruise controls the engine via EDC ............ 7
Gear changing sequence, description ................ 8
Engine brake program ....................................... 9
Starting gear, programming .............................. 9
Kick-down ..........................................................9
Auxiliary brake system ......................................9
EDC cruise control .......................................... 10
ABS/TC ............................................................10
Power take-offs ................................................10
Configuration, control unit .............................. 11
Power supply and fuses ................................... 11
Interaction with other systems ........................ 12
Opticruise, design .............................................14
Warning system ................................................16
General .............................................................19
Faults that do not generate fault codes ............ 19
Electrical system
Mechanical work
Exploded view drawings
Clarifications, new terms ................................ 20
List of fault codes ....................................... 19-52
References to wiring diagrams ........................ 53
Location of electrical components .............54-55
Control unit signals .................................... 56-59
Driving mode selector ......................................60
Test program .............................................. 61-71
General .............................................................73
Instructions for repair and adjustment ....... 73-76
Components on gearbox ............................. 77-83
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General
General
Opticruise in brief
Opticruise is a system which allows a normal
manual gearbox to shift automatically. The
clutch is retained but is used only when starting, stopping and shunting.
A control unit collects and processes data from
controls, sensors and adjacent systems such as
EDC, ABS/TC and auxiliary brake (if fitted).
When it is time to change gear, the control unit
actuates the solenoid valves, releasing compressed air to the air cylinders. These air cylinders then change to the required gear.
The control unit has an in-built warning system. Fault codes can either be read on the display or using a PC and the Scania Diagnos
program. The latter makes fault diagnosis
quicker.
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Opticruise requires that the vehicle be fitted
with both EDC and ABS/TC, due to the information exchange requirements between the
systems.
When changing gear, the engine speed is controlled so that the speeds of the gearbox input
shaft and output shaft correspond for the gear
to be engaged. Gear changing is only then
completed.
When necessary, the exhaust brake is used to
make changing up fast and smooth.
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General
Introduction
Scania Opticruise is an automatic gear changing system for
manual gearboxes. Opticruise is constructed in more or less
the same way as the Scania CAG system, the major difference
being that the driver only needs to use the clutch pedal when
starting, stopping and shunting.
The system is able to change gear automatically without the
clutch because the engine is regulated to synchronous speed
for the gear that is to be engaged. This means that the electronics adapt both engine speed and torque to exactly the levels required by the gearbox. This makes all gear changing
gentle and precise, increasing the service life of the entire
powertrain.
Opticruise requires the engine to be equipped with EDC. It
would not be possible, using a mechanical injection pump, to
control the engine with the speed and precision required for
Opticruise to work smoothly. Opticruise also requires the
vehicle to be equipped with ABS/TC in order to select the
correct gear, even if the drive wheels lose grip on a slippery
road surface.
Using Opticruise, the driver can choose to drive with manual
or automatic gear selection. In manual gear selection driving
mode, the driver selects the gear and when it is changed
(depending on road speed and/or engine speed). The control
unit decides whether it is possible to change gear without the
driver using the clutch. If this is the case, the gear is immedi-
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ately changed when the driver moves the driving mode selector sideways. Otherwise, the driver has to depress the clutch
pedal in order to change gear.
Normal
Hill
In automatic gear selection driving mode, the control unit calculates which gear is appropriate and carries out this shift
when the calculation is complete. In this case, gear changing
always takes place without the driver having to use the clutch
pedal. If the EDC cruise control is engaged, gear change is
automatic without the cruise control being disengaged. This
applies until speed is so low that it is a question of stopping or
shunting. The clutch must then be used.
In addition to the driving mode selector and its various positions, the driver can choose between two different driving
programs. This is done using a program selector beside the
driving mode selector. These programs are called Normal and
Hill. The Hill program is for steep upward slopes with more
than 5 % gradient.
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CLU MODE
LIMPHOME
General
The control unit varies the point at which it changes gear,
depending on the position of the program selector. When driving with the program selector set to Hill, gear changing is
faster than when the Normal program is engaged. If necessary, the exhaust brake may also be used in order to quickly
reduce the speed of the engine.
Like the older CAG system, Opticruise has a selectable starting gear which is programmed in one of the control unit memories. The driver can easily select the starting gear for the
average gross train weight of the vehicle combination. The
control unit retains this setting, even when power is interrupted. In addition to this, the driver can temporarily select a
starting gear other than the one programmed in the memory.
This is fully described in the driver’s manual.
The control unit has a built-in warning system. This has made
it possible to reduce the inconvenience in the event of a fault.
Opticruise has two built-in emergency driving programs. The
first of these, clutch mode, is activated in the case of less serious faults and the driver has to depress the clutch pedal every
time a gear is changed. If the driving mode selector is set to
automatic, Opticruise still preselects the gear as normal. In
this situation, Opticruise works in the same way as Scania
CAG.
In the case of more serious faults, the driver should activate a
limp home program. This makes it possible to drive the vehicle to a workshop, even if something like a sensor is faulty.
This means that the vehicle can be run, even if the emergency
driving program feels basic with its manually-requested compressed air gear changes.
The Opticruise system interacts with the braking effect of the
diesel engine, the exhaust brake and the Scania retarder, if the
vehicle is fitted with this. This reduces brake wear, reducing
running costs. In addition, wear to the entire powertrain is
reduced as power is transferred more gently than on vehicles
with manual gearboxes.
However, the greatest advantage, not least financially, is of
course improved driver comfort. Opticruise enables the driver
to maintain concentration longer than when driving a vehicle
with manual gear changing. This is an advantage for both running costs and road safety.
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General
Controls and operation
3
The above drawing shows the controls used for
Opticruise. The clutch pedal, controls for EDC
cruise control and auxiliary brake control unit
also affect the system.
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4
1
2
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1 Driving mode selector with positions R, N,
A and M. The driver is able to command up
and downshift by moving the selector lever
to the side.
For example, the auxiliary brake may request
that the engine brake program be activated in
order to increase engine speed and therefore
coolant flow. This is essential for optimum
retarder performance.
When driving with the cruise control, the system changes gear automatically provided the
driving mode selector is set the position A. The
cruise control is deactivated using the clutch
pedal, brake pedal, retarder lever, cruise control OFF button or using the exhaust brake
switch on the floor.
2 Program selector with Normal and Hill
positions. The Hill position is for use on
steep slopes, preferably with the driving
mode selector set to M (manual).
3
Switch for activating engine brake program and exhaust brake.
4
Diagnostics switch
5
Gear indicator with display and buzzer.
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Description of operation
Description of operation
Gear changing
Driving in automatic position A means that the
system changes gear automatically in accordance with the driving program set using the
program selector, either ”Normal” or ”Hill”.
However, the gear selected automatically can
be changed at any time by the driver by moving the driving mode selector to the side. The
control unit always checks that the driver’s
selection is within reasonable limits.
The driver can even preselect a gear that
appears completely inappropriate under the circumstances, such as 3rd when driving in 7th.
There are two conditions that must be met for
this to work.
• The vehicle must lose speed (be retarded).
• The driving mode selector must be set to
manual and the program selector to Hill.
The gearbox then starts the shift by first going
to neutral. The control unit then prepares itself
for the correct splitter level, correct lateral
stroke and the correct range before road speed
is reduced sufficiently for the particular gear
change to be requested.
At the same time, engine speed is automatically increased to high idling, about 2500 rpm.
When road speed has decreased sufficiently,
the gear is engaged smoothly and gently. When
gear changing is complete, control of the
engine is returned to the driver.
When driving, the driver can at any time move
the driving mode selector to neutral (N) when,
for example, approaching a traffic light. If he
changes his mind and the vehicle is still moving, it is possible to move the driving mode
selector back to one of positions A or M. The
control unit then selects a suitable gear, based
on the speed of the vehicle and other information from sensors etc. It is not necessary to use
the clutch unless speed is too low.
From automatic position A, the driver can at
any time move the lever to manual position M
and vice versa. This can be useful if you, for
example, want to ”lock” a gear on a slippery
road surface. The same applies if he wants to
shift manually, for example on steep hills.
Note: On uphill slopes greater than 8 %, it may
be necessary to drive with the driving mode
selector set to M and with the program selector
set to ”Hill”. This gives the fastest possible
gear changing, which means that the vehicle
does not lose so much speed during changing.
Opticruise controls the engine via EDC
Gear changing when driving is done by
Opticruise controlling the engine via EDC to
synchronous speed for the gear that is about to
be engaged, without the driver using the clutch
pedal. This means that both engine speed and
torque are adjusted to precisely the level
required by the gearbox.
In order to make gear changing easier, engine
torque is reduced in a controlled manner just
before the gear is disengaged.
Gear changing takes place after the speed of
the moving parts in the gearbox has been synchronized.
Towards the end of gear changing, engine
torque increases in a gentle and controlled
manner to the level requested by the driver
using the throttle pedal. This means that gear
changing is always gentle and precise, increasing the service life of the entire powertrain.
This precise control is made possible by communication between the Opticruise and EDC
control systems.
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Description of operation
Description of the gear changing process
1 Gear change requested automatically or by the driver.
2 Engine regulated so that there is no torque on the gearbox
input shaft.
3 Gearbox set to neutral.
4 Engine regulated to synchronize the speed of the gearbox
input shaft and the moving parts for the gear to be
engaged.
5 Gear engaged.
6 The engine is regulated to the required torque. The
Opticruise then returns control of the engine to the driver.
• During certain upshifts, the exhaust brake is used to more
quickly brake the engine to the correct speed in relation to
the gear selected.
• When driving in automatic (A), the control unit continuously calculates which gear is most suitable. When this calculation shows that a gear other than the one engaged
would be more suitable, the gear change takes place immediately. This may be either a single change or a block
change.
The calculation of appropriate gear is made based on the following data:
- Position of program selector
- Current road speed
- Current acceleration
- Current torque
- Total gear ratio
- Throttle pedal position
- Any request for the activation of the engine brake program
from the driver or from the auxiliary brake control unit.
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Description of operation
Engine brake program
The function of the engine brake program is to
give optimum engine braking in all driving
conditions. The engine brake program has
nothing to do with the Normal/Hill program
selector, but is controlled by a separate switch
on the floor of the cab.
In order to use the engine brake program, the
throttle pedal must be fully released.
A short press on the floor switch is all that is
required to activate the engine brake program.
This means that upshift is delayed as the control unit maintains the gear for longer before
changing up, increasing engine brake output.
However, if the floor switch is held down all
the time, the exhaust brake is also engaged and
downshift takes place earlier.
If the brake pedal is held down, the upshift
points change. The control unit is informed of
this via the brake lamp switch.
The engine brake program is connected until
the throttle pedal is next depressed.
If the vehicle is equipped with an auxiliary
brake system with Scania retarder, the engine
brake program can be automatically engaged
(if appropriate) when using the retarder. This is
done by the auxiliary brake control unit. The
intention is to raise engine speed and thus coolant flow, providing the retarder with maximum
braking effect and activation time.
Programming start-off gear
The system permits free choice of starting gear
between 1st and 4th. 1st or 2nd are normally
used, but it may be appropriate to use another
one in extreme cases.
Note: When the vehicle is heavily loaded, 1st
or 2nd must be used. Otherwise, the clutch
will be subjected to excessive wear.
It may sometimes be necessary to start in a
gear other than the one programmed. This can
be done, irrespective of whether the driving
mode selector is set to A or M. Simply move
the driving mode selector to the side until the
required gear is shown on the display. The
vehicle can now be started. The ordinary starting gear remains programmed in the control
unit memory. More information can be found
in the driver’s manual.
Kick-down
By pressing the throttle pedal from full throttle
to kick-down, the gear changing points are
raised, usually causing faster downshift.
Auxiliary brake system
See ”Engine brake program”.
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Description of operation
EDC Cruise control
When driving with the cruise control, the system automatically change gear if the driving mode selector is set to A. It is
however still possible to manually control gear selection in
both positions A and M, without disengaging the cruise control.
If the driving mode selector is set to N when the vehicle is
being driven with the cruise control activated, engine speed is
increased to high idling (i.e. the engine surges). The driver
should therefore disengage the cruise control before setting
the driving mode selector to N.
The cruise control is disengaged using the clutch pedal, brake
pedal, retarder lever, cruise control OFF button or the exhaust
brake switch on the cab floor.
ABS/TC
The Opticruise control unit communicates with the ABS/TC
system. If there is wheel lock (causing ABS control) or spin
(causing TC control), the Opticruise is very reluctant to
change gear and does so according to special criteria. When
the driving mode selector is set to A, the Opticruise endeavours to maintain the engaged gear.
Power take-offs
The control unit is configured for two types of power take-off,
PTO EK/ED and PTO EG.
PTO EK/ED provides torque compensation and therefore very
smooth gear changing if the vehicle is driven with an enginedriven power take-off engaged (Max. compensation 200 Nm).
If the ED120 is used to drive a hydraulic pump, there may be
a lack of space around the longitudinal stroke cylinder. If this
is the case, turn the longitudinal stroke cylinder the other way
and move the compressed air couplings so that they swap
places.
PTO EG is for gearbox-driven power take-offs. If the vehicle
is driven with this input signal active, all gear changing is
blocked. The text PTO also flashes on the display if the vehicle is driven above a certain speed.
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Description of operation
Miscellaneous
Control unit configuration
The control unit contains all programming necessary for a number of different Scania versions. So that the control unit fits each Scania,
it must first be configured so that it uses the
correct program for the particular vehicle. This
is equivalent to the code plug in other (less
modern) control units, such as for CAG.
The required configuration is fed into the control unit at manufacture using a PC. Configuration may be changed later by qualified
personnel.
Configuration must contain the following
information:
• Vehicle category (e.g. truck)
• Chassis number
• Part No. for control unit software
• Gearbox type
• Engine type and version
Power supply and fuses
Generally, Opticruise continues to work if a
fuse blows while the vehicle is being driven. It
may, however, be impossible to start the system the next time.
The control unit is protected by two fuses:
• Fuse 41 is used for 30 supply.
• Fuse 5 is used for 15 supply.
Power to the control unit is usually interrupted
using the starter switch. What happens then is
that control unit 15 supply to pin 55 is broken.
When this happens, important data is transferred from the RAM to the EEPROM and
stored there until the next start. The control
unit then goes into rest state, despite the fact
that 30 supply from the batteries is still applied
to pin 19.
• If fuse 41 for 30 supply blows, or if a battery cable is removed, data cannot be transferred from the RAM to the EEPROM and
be stored. The control unit ”forgets” any
newly-programmed starting gear as well as
new fault codes.
• Rear axle ratio
• Wheel rolling radius
• End-of-line data (date, signature)
• If fuse 5 for the 15 supply blows, data is
transferred as normal from RAM to EEPROM and stored there. In this situation, the
control unit believes that the starter key has
been set to position 0. This means that it is
not possible to restart Opticruise until the
fault has been corrected.
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Description of operation
Interaction with other systems
The figure opposite shows which other systems
are connected to Opticruise and in which
directions data is transferred.
Any faults are transmitted in the same
direction. This means that a fault in the
ABS/TC system can manifest itself in the
Opticruise system, but not vice versa.
Where appropriate, the figure applies to all
optional equipment affected.
• The Opticruise is coupled to the EDC system to enable synchronous control of the
speed of the gearbox input and output
shafts. The particular gear change does not
take place until these speeds correspond
with each other.
The communication between the Opticruise
and the EDC covers a wide range of data,
such as engine speed, requested and actual
torque, throttle pedal position, coolant temperature and cruise control.
Communication is via two CAN leads and is
for such things as executing engine-controlled gear changing and determining which
gear should be selected at any particular
time.
• Opticruise is coupled to the auxiliary brake
system to make it possible to engage the
engine brake program to optimize the
retarder and achieve maximum braking
power in kW.
When the auxiliary brake has requested the
exhaust brake to retard the vehicle, the
Opticruise will still be able to control the
exhaust brake for gear changing.
When the gear change is complete, the
exhaust brake will again be used to retard
the vehicle. Prioritization of the various
tasks of the exhaust brake is controlled by
the exhaust brake control unit (EEB).
If the vehicle has an auxiliary brake, the
Opticruise forwards the speed signal from
the speed sensor on the gearbox output shaft
to the auxiliary brake control unit.
• Opticruise is connected to the tachograph so
that it can use the speed information from
this to check that other speed signals are
reasonable.
12
• The Opticruise is coupled to the ABS/TC
system to receive information on ABS control, TC control, wheel speeds etc.
The communication between Opticruise and
ABS/TC is used for confirming such things
as the suitability of the gear selection. If the
wheels are spinning or slipping, Opticruise
would be “fooled” into selecting the wrong
gear. The speed of each wheel is also used
to check that other speed signals appear
plausible.
Communication is via the two CAN leads.
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Opticruise
Exhaust brake
Description of operation
ABS/TC
Auxiliary brake
system with
Scania retarder
EDC
Tachograph
Signal paths between the Opticruise control unit
and other computer-controlled systems that
in the vehicle.
Any faults are transferred from one system to
another in the same direction as communication
(see arrows).
may be
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Scania CV AB 1995 13
Description of operation
Opticruise, design
Item numbers refer to the drawing opposite.
1 The floor switch is used to activate the
engine brake program and exhaust brake.
In vehicles with no auxiliary brake, the
exhaust brake is used in combination with
the engine brake program when the floor
switch is held down. The signal goes via
the auxiliary brake control unit if the vehicle has this. Also see point 14.
2 Two switches provide data on the position
of the clutch pedal (released, partly or fully
depressed).
3 EDC informs the control unit that the
driver is braking. The engine brake program then uses slightly shifted upshift
points.
4 The tachograph provides a speed signal
which Opticruise compares with the other
speed signals. These come from ABS/TC
and the gearbox output shaft.
5 The throttle pedal sensor provides data on
requested throttle and kick-down. The
potentiometer signal goes via the EDC
control unit.
6 The gear indicator with display and buzzer
is used to display driving program, which
gear is engaged, fault messages etc.
8 The driving mode selector informs the con-
trol unit about requested driving mode and
if the driver wants to actuate the automatic
system by commanding a change up or
down.
12 The diagnostic switch is used to activate
the test program built into the control unit
and for erasing fault codes.
13 Opticruise receives information from
ABS/TC on speed, slip and possible wheel
spin in order to select the correct gear at
any moment. In addition, Opticruise must
be able to prevent gear change if the drive
wheels lose grip. This is for safety.
14 Opticruise uses the exhaust brake to adapt
engine speed during certain gear changing
procedures, but the exhaust brake is normally used to brake the vehicle.
The exhaust brake control unit prioritizes
requests depending on driving conditions.
The exhaust brake can be activated automatically, manually or by the auxiliary
brake control unit.
15 The engine speed sensor is used to be able
to synchronize the speeds of the gearbox
input and output shafts when changing
gear. The signal goes via the EDC and
through the communications circuit.
16 The solenoid valves on the gearbox carry
out each gear change by releasing compressed air to the longitudinal and lateral
stroke cylinders. In turn, the cylinders activate the gear selector shaft.
17 The hall effect sensor and the confirmation
switches monitor and confirm gear changing movement.
14
9 The program selector has two positions.
The Normal position provides optimum
fuel economy and the box changes gear
calmly and comfortably. The Hill mode
provides a faster gear changing cycle at
higher engine speed.
10 Diagnostic socket for PC via interface
(Scania VCI).
11 PC with Scania Diagnos 2 fault tracing
program provides the fastest result when
fault tracing.
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Description of operation
The drawing below is general and applies to all optional equipment affected. Only relevant sections apply to vehicles with less equipment.
PTO EK/ED
PTO EG
RETARDER
EDC
10
4
1
3
2
21
22
20
19
12
5
6
8
OPTI−
CRUISE
15
16
17
9
14
13
18
11
ABS/TC
18 The speed sensor on the gearbox output
shaft is used to calculate vehicle speed and
to confirm other speed signals from
ABS/TC and the tachograph. A corresponding output signal is relayed to the
auxiliary brake control unit.
19 Control of engine torque and speed is
requested by Opticruise but carried out by
EDC. Just when Opticruise is controlling
the engine, the control unit continuously
checks that actual torque corresponds to
the requested level.
20 The auxiliary brake system control unit can
request Opticruise to activate the engine
brake program.
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21 PTO EK/ED provides torque compensa-
tion during engine-controlled gear changing and therefore an excellent level of
comfort if the vehicle is driven with an
engine-driven power take-off engaged.
22 PTO EG is for gearbox-driven power take-
offs. When this input signal is active, all
gear changing is blocked and the clutch
cannot be used.
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Scania CV AB 1995 15
Description of operation
Warning system
The control unit takes various action in the case of faults. This
is to prevent the fault having expensive consequences. For
example, the control unit has two different emergency gear
changing programs. The first of these still provides good drivability while the second requires more from the driver. The
intention of this is that minor faults should not cause too much
inconvenience.
CLU MODE
C
NORMAL
FAILURE
Certain types of less-serious fault cause the control unit to
switch from normal operation to the simpler of the two emergency gear changing programs. The text ”CLU MODE”
(clutch mode) is shown on the gear indicator display. In this
case, the driver is required to use the clutch for each gear
change. While the control unit is working in this mode, the
letter C will be displayed near the left of the display.
If the fault disappears on its own, the control unit immediately
returns to normal operation. The display then shows ”NORMAL”.
In the case of more serious faults, ”FAILURE” is displayed. If
this happens when driving, the control unit locks the engaged
gear. This gear alone is shown on the display. The driver must
then stop the vehicle and activate the ”LIMPHOME” emergency gear changing program. This process is described in
detail in the Opticruise driver’s manual.
16
CHK CODE
ERROR1
ERROR2
CONFIG
Fault code messages
When the driver switches off the power, the message ”CHK
CODE” is displayed if the control unit has stored any fault
codes during driving. This message is repeated when the
power is switched back on again.
”ERROR1” or ”ERROR2” means that the control unit has
supplied faulty signals or no signals to the display. A PC must
be used to read any fault codes.
”CONFIG” means that the configuration of the control unit is
not correct. In this case, change the configuration of the control unit using a PC and Scania Programmer.
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Description of operation
Reading fault codes
Fault codes are read in the first part of the Opticruise test program. This test program is described in full on pages 59 - 69
of this booklet.
However, describing how to read fault codes would be a suitable introduction to the list of fault codes in the next chapter
and the method is therefore also shown here.
1 Stop the vehicle and switch off the engine.
TESTING
ECU NO
PROG NO
CHASSNO
F CODES
2 Switch on the power using the starter key.
seconds and then hold the diagnostic switch depressed for
at least a half second. Release it. ”TESTING” is shown on
the display and the buzzer sounds.
Do not touch the diagnostic switch for the moment. The
test program has now started. All parts of the display light
for one second and the buzzer sounds.
3 ”ECU NO” is displayed, directly followed by the part
number of the control unit hardware.
4 ”PROG NO” is displayed, directly followed by the part
number of the control unit software.
5 ”CHASSNO” is displayed, directly followed by the vehi-
cle chassis number.
6 ”F CODES” is displayed, directly followed by any fault
codes stored. More on this below.
• The fault codes are displayed one at a time, with two seconds between them.
Wait for five
E010 003
A
B
• When all stored fault codes have been displayed, the
buzzer sounds briefly. The stored fault codes are then displayed again. This may be repeated any number of times,
so there is no danger if you should lose concentration.
The display can, for example, look like the figure to the
left. A shows the number of the fault code (10 in this case)
and B shows how many times this fault code has been registered (3).
7 Make a note of the fault codes. Run through the test pro-
gram. Press the diagnostic switch to switch between the
various stages of the test. See pages 59 - 69.
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Description of operation
Erasing fault codes
It may be necessary to reset the warning system
every now and then. Someone may, for example, have unplugged a cable while the power
was switched on. This can easily happen and the
control unit will then believe that a genuine fault
has arisen.
The warning system is either reset using the
diagnostic switch, concealed behind the cover
on the instrument panel, or using a PC connected to the vehicle’s diagnostic socket in the
central electric unit.
Fault codes are extremely useful in the workshop as they facilitate fault diagnosis.
• In the driver’s manual, there is an explanation of how to erase fault codes. However, it
is also advised that they should not be erased
unnecessarily and that it is preferable, if possible, to seek advice at a workshop.
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The symbols for the various switches are on the
inside of the lid. These can be seen when the lid
is opened. The Opticruise symbol is shown to
the right.
When the warning system is reset, all fault
codes are erased. Proceed as follows:
1 Switch off the power using the starter key.
2 Press the diagnostic switch and hold it
down. Switch on the power.
3 The buzzer gives a short signal. When the
text ”ERASED” is displayed, erasure is
complete.
ERASED!
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Fault codes
General
The control unit acts fast and accurately, according to certain
instructions. It has no imagination and no judgement. When it discovers a fault, or anything it interprets as abnormal, it reacts
immediately and generates fault codes. The warning system is
capable of generating around 70 different fault codes.
Fault codes
Despite the advanced and ”farsighted” software, a fault can arise which the control unit is
unable to distinguish from something which
might happen during normal operation. If this
is the case, no fault code is generated. There is
always a limit to how complete monitoring can
be. This applies to all types of control unit.
Limitations
It is not only ”genuine” faults that lead to the
generation of fault codes. It is sufficient that
someone has unplugged a cable while the
power was on. This can easily happen and the
control unit will then believe that a fault has
arisen.
As for cases of loose contact, the fault may no
longer be present, but the fault code is stored in
the control unit memory until it is erased. It is
at least possible then to see which circuit the
fault was in and look for the cause there, even
if there is currently no fault.
Faults that do not generate fault codes
The following are the faults which do not cause
a fault code to be generated that we are aware
of at the time of going to press.
• Fuse 5 blown (15 supply).
• Break in the diagnostics switch circuit.
• Break in the floor switch circuit.
• Break or continuous signal from program
selector (Normal/Hill).
• Break in circuit to the exhaust brake control
unit. Fault code 14 is generated in some, but
not all, cases.
• Break to gear indicator.
• Broken lamp in gear indicator.
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Fault codes
Explanations
Several new terms are used in the fault code
list or in the connection diagram in group 16.
These terms are explained below.
EEPROM: Stands for electrically erasable
programmable read only memory. Memory is
retained, even if power is broken using the
starter key. The contents can be erased and
updated during service, using a PC and Scania
Programmer.
This memory contains the control unit configuration, programmed starting gear, any fault
codes etc.
FLASH memory: This memory contains the
complete basic programming of the control
unit. The content remains, even if power is
switched off using the starter key. The basic
program can be changed during service using a
PC connected to the diagnostic socket.
RAM: Stands for random access memory. The
content disappears every time the power is
switched off using the starter key or if power is
lost for any other reason.
This memory stores and processes the various
control unit driving data from such things as
sensors, controls and adjacent systems (EDC,
ABS and the retarder).
CAN: Stands for controller area network. CAN
communication is used to reduce the number of
cables in the vehicle. This is intended to
increase reliability.
Vehicles with Opticruise have a communications circuit consisting of two cables, CAN
high (pin 38) and CAN low (pin 20).
In simple terms, CAN communication can be
likened to radio technology. Data signals
through a CAN cable can be likened to radio
waves through the air.
When listening to the radio, the receiver is set
so that one radio station is heard at one time.
This is the only station that can be heard,
despite the fact that there are many radio stations broadcasting at the same time.
A control unit does more or less the same thing
with the data coming through a CAN cable. It
listens for things such as information from
EDC on coolant temperature, receives this
value and uses it in calculations.
The control unit receives all CAN signals that
are sent through the communications circuit in
a special memory. This memory can be likened
to a number of radio receivers, set to different
radio stations in order to hear several, particular radio programmes at the same time. In this
way, the control unit always knows what is
happening.
This is nothing that a mechanic needs to worry
about.
The only thing to remember is that it is
not possible to check CAN signals using a multimeter. This is not even necessary as we have
precise fault codes.
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Fault codes
Fault code 1
Fault code 2
Fault: Fault in integrated control unit memory.
Cause: Test calculation of content of FLASH memory did not
provide the result the control unit was expecting.
Comment: FLASH memory itself contains basic control
unit program. The control unit checks that the FLASH memory is working as follows. All memory addresses are added
together to provide a sum. This sum is then used in a test calculation which must provide the ”correct answer”. Otherwise,
this fault code is generated.
Action: Change control unit.
Fault: Fault in integrated control unit memory.
Cause: Test calculation of content of EEPROM memory did
not provide the result expected by the control unit.
Comment: EEPROM memory contains the configuration of
the control unit. Configuration controls which parts of the
basic program are used for the particular vehicle. When the
control unit checks that the EEPROM memory is working, the
following happens. All values that are important for configuration are added up to a sum. This sum is then used in a test
calculation which must provide the ”correct answer”. Otherwise, this fault code is generated.
Fault code 3
Action: Correctly configure the control unit using a PC. If
this does not help, change the control unit.
Fault: Fault in integrated control unit memory.
Cause: The control unit’s test of the RAM has shown that
some of the memory cells are not working properly.
Comment: The RAM is the actual working memory of the
control unit. It is here that all calculations are made.
When the control unit checks that the RAM is working prop-
erly, the following happens. Firstly, the control unit writes
certain values into the RAM and then reads these same values
to check that they have not become confused . If the control
unit interprets any deviation, this fault code is generated.
Action: Change control unit.
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Fault codes
Fault code 4
Fault: Break or short in circuit for UX supply.
Cause: Control unit has detected that power consumption
from pin 36 on the control unit (the so-called UX feed, +24V)
is either too low or too high.
Comment: The control unit gives UX supply on pin 36 to
supply the sensors, controls and display with power. The UX
supply enables the control unit to sense both open and short
circuits as they cause abnormal power consumption. It is this
abnormal power consumption from pin 36 which causes fault
code 4 to be generated.
Open circuit: The circuit consumes no current. Short circuit:
The circuit consumes high current.
In order for the fault code to be regenerated, power consumption must suddenly change, due to something such as loose
contact. If the fault remains, the fault code is regenerated each
time the control unit attempts to activate the UX supply.
Fault code 5
High current in the UX circuit can be caused by such things as
shorted sensors.
Action: Check the UX circuit, wiring and components.
Fault: Fault in voltage supply in control unit.
Cause: Control unit could not confirm its own internal U15
supply when the driver switched on the power using the
starter key.
Comment: The control unit started working when the power
was switched on, despite it not being possible to confirm U15
supply in the test circuit monitoring this.
When this fault arises, it is not possible for the EEPROM to
store new information. This means that the control unit ”forgets” any newly-programmed starting gear, and any newlygenerated fault codes. The number of faults is displayed as 1,
even if there are several. It is possible to drive the vehicle, but
it should be repaired as soon as possible as certain safety features may be jeopardized.
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Action: Change control unit.
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Fault code 7
Fault codes
Fault: Fault in monitoring feature inside control unit.
Cause: The integrated watchdog relay does not activate when
the control unit starts working, or this relay is already activated when the driver switches on the starter power (this
should not be the case).
Comment: The control unit has detected a malfunction in one
of its internal safety features. Each malfunction of this type
causes the watchdog relay to alarm, generating fault code 7.
If the watchdog relay does not activate, power supply is lost to
all control unit outputs. Not even the starter gear can be
engaged, making the vehicle unusable.
Action: Change control unit.
Fault code 14
Fault: Not possible to regulate engine speed to correct level
when changing gear.
Cause: The control unit has received a message from the
EDC via the communications circuit (pins 20 and 38) which
indicated an incorrect response from the engine. The exhaust
brake may have been activated during gear changing without
the Opticruise requesting this.
Comment: Requested torque exceeds permitted value for
engine-controlled gear changing when the gearbox has been
confirmed to be in neutral. This can happen if a gear is
engaged when the control unit is not expecting it. A possible
cause of this might be the slider in the gearbox breaking. If
this fault arises, the driver must use the clutch for every gear
change. CLU_MODE is displayed.
Action: Start by checking the sensor signals for gear position
and then the gearbox itself.
Fault code 15
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Fault: EDC gives a torque which does not correspond to the
requested torque.
Cause: When the Opticruise control unit requested a particular torque via the communications circuit (pins 20 and 38),
EDC responded with a response which Opticruise considered
to indicate impossible values.
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Continued >
Fault codes
Comment: Requested torque from Opticruise is ”translated”
in this manner to actual control rack position in the injection
pump. The Opticruise control unit continuously checks that
each response of this type from EDC corresponds with the
expected result. If this fault arises, the driver has to use the
clutch whenever changing gear. CLU_MODE is displayed.
Action: Check whether the EDC control unit has generated
any fault codes. Check that the EDC control unit has the correct part number. Check connectors and wiring. End by
checking the position of the control rack in the injection
pump.
Fault code 19
Fault: NO signal or impossible signal from driving mode
selector.
Cause: The control unit has received a signal on at least two
of pins 10, 11, 28, 29, 47 and 48 at the same time, or there is
no signal at all from the driving mode selector. These signals
are provided with UX voltage (+24V).
Comment: These signals are impossible as the driving mode
selector can only be in one position at a time.
If this fault arises, the control unit does not ”obey” the driving
mode selector. Either there is no signal at all, or the control
unit has received conflicting signals in one of the following
combinations:
Upshift and downshift at the same time (pins 10 and 28).
Reverse and automatic position at the same time (pins 48
and 29).
Reverse and manual position at the same time (pins 48
and 47).
24
Neutral and manual position at the same time (pins 11
and 47).
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Continued >
Fault code 22
Fault codes
Action: Check the driving mode selector, connectors and wiring. Use wiring diagrams and a multimeter to check the driving mode selector.
Fault: Impossible signals from clutch switches.
Cause: Control unit has sensed that pin 8 received a signal
when there was no signal on pin 45.
Comment: The lower clutch pedal switch has been closed
despite the upper clutch pedal switch not being closed. It
should not be possible for something like this to happen when
driving.
When these switches are activated, they are closed to system
earth (0V).
Fault code 23
The gearbox cannot change gear automatically if this fault has
arisen. The vehicle can, however, be operated using the LIMPHOME emergency gear changing program.
Action: Check both clutch pedal switches, connectors and
wiring.
Fault: Uninterrupted signal from the lower clutch pedal
switch.
Cause: Control unit has sensed that there was a signal for too
long on pin 8.
Comment: The clutch pedal switch cannot be closed for this
long when driving normally.
When this switch is activated, it is closed to system earth
(0V).
The gearbox cannot change gear automatically if this fault has
arisen. The vehicle can, however, be operated using the LIMPHOME emergency gear changing program.
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Action: Check the lower clutch pedal switch, connectors and
wiring.
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Fault codes
Fault code 24
Fault: Uninterrupted signal from upper clutch pedal switch.
Cause: Control unit has sensed that the signal remained for
too long on pin 45.
Comment: The clutch pedal switch cannot be closed for this
long when driving normally, unless the driver rests his foot on
the clutch pedal when driving.
When this switch is activated, it is closed to system earth
(0V).
The gearbox cannot carry out engine-controlled gear changing
in manual position if this fault arises.
Action: Check the upper clutch pedal switch, connectors and
wiring.
Fault code 26
Fault: Uninterrupted signal from floor switch for engine
brake program.
Cause: Control unit has sensed that the signal remained for
too long on pin 27.
Comment: The floor switch cannot be closed for this long
during normal driving.
When this switch is activated, it is closed to +24V. Note that
the signal to pin 27 does not always come from the floor
switch. The retarder control unit can also send the same signal.
If this fault arises, the control unit is forced to use the engine
brake program.
Action: Check the floor switch, connectors and wiring. Check
if there are any fault codes stored in the retarder control unit
(if the vehicle has a retarder).
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