2008 RENAULT SCENIC Electrical Equipment - Multiplexing Workshop Manual

MULTIPLEXING
Fault finding - Features
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1) The transmitting computer formats the signal to be
transmitted into a frame that can be identified by
other computers.
2) The transmitting computer waits for the network to
be free, i.e. no frames are being transmitted by
another computer.
3) The computer can then transmit its frame.
4) All the other computers receive the transmitted
frame. As the frame has already been formatted
by the transmitting computer, the receiving
computer can determine whether the frame was
meant for it or not.
5) The receiving computers acknowledge the frame
to confirm that the frame has been received. The
transmitting computer will resend the frame if it
does not receive this acknowledgement.
Transmitting frames
The frames are transmitted on two twisted wires in
order to avoid electromagnetic interference. These
wires are called multiplex line H and multiplex line L.
To reduce electrical interference when frames are sent,
the two wires have differential voltages. In addition,
terminating resistances of 120 Ω are fitted at the ends
of the network (in the airbag and injection computers)
to attenuate electrical signal reflections.
The electric signals are digital which means that there
can only be two levels of differential voltage known as
recessive status (corresponding to logic 1) and
dominant status (corresponding to logic 0).
The status is recessive when the potential difference
between multiplex line H and multiplex line L is zero
(multiplex line H = multiplex line L = 2.5 V). The status
is dominant when the potential difference between
multiplex line H and multiplex line L is equal to
approximately 2 V (multiplex line H = 3.5 V and
multiplex line L = 1.5 V).
Content of the frame
A multiplex line frame comprises several groups of
contiguous bits:1A field indicating the start of the frame.
2An arbitration field with a destination code so that
receiving computers can recognise the frame. In
addition, this field decides on frame priority when
several computer want to send a frame at the
same time.
3A test field which supplies various information
about a frame.
4A field containing the data to be transmitted.
5A frame confirmation field which ensures that the
signal is correctly transmitted as well as the
acknowledgement indicating that the frame has
been correctly received.
6A field indicating the end of the frame.
Fault finding
Multiplex computers fitted with diagnostic connections
have multiplex network fault finding systems.
Each computer monitors its capacity to send and
receive frames to and from other computers. Any
observed fault is revealed by one or several present or
stored faults on the multiplex network. These faults are
grouped under a format common to all computers and
are communicated via a special frame to the
diagnostic tool.
In the After-Sales Centre, these faults can be viewed
on a diagnostic tool in order to identify the faulty
connections(s) between computers and to deduce the
fault type and its location.
The diagnostic tool always runs a multiplex network
test when it is connected to the vehicle.

MULTIPLEXING
Fault finding - Defect and safe modes
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MULTIPLEXING
Fault finding - Defect and safe modes
The multiplexing function does not have a safe mode
program.
However, the multiplexing function may have special
operation features.
The multiplex network still functions when multiplex
line L is in short circuit to earth. The voltage on
multiplex line H is no longer differential; it corresponds
to earth.
MR-372-J84-88B050$500_eng.mif

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MULTIPLEXING
Fault finding - Configuration
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MULTIPLEXING
Fault finding - Configuration
MULTIPLEX NETWORK CONFIGURATION
The tool displays the UCH and Airbag configurations.
The Configuration screen consists of two tabs for displaying and modifying:
–The first tab: Multiplex network configuration indicates the multiplex network version and the list of computers
defined as present on the multiplex network.
–The second tab Configuration of computers supporting fault finding indicates the relevant diagram number,
and the list of computers defined as able to support fault finding with the CLIP tool.
NOTESThe configuration is entered with the ignition on; apply the forced + after ignition
feed procedure (see Introduction).
It can be run from the multiplex network test results screens.
WARNING
Enter the correct diagram version number,
–Scénic II ph1: version 1.
–Scénic II ph2: version 2 with ITS (Vdiag 04) navigation computer.
–Scénic II ph2: version 3 with 4R or other navigation computer (Vdiag 24) or without navigation computer.
–Scénic II ph2: version 4 with LPN navigation computer.
First repair the computers containing the multiplex network configuration (airbag and UCH) to be able to
display the screen with the multiplex network configuration diagram for the diagnosed vehicle.
IMPORTANT
A computer connected to the multiplex network but not declared as being among the computers containing the
multiplex network configuration will not be checked in the multiplex network test.
Correct the configuration by declaring the computer as present if it is absent in the Airbag and UCH computer.
Carry out the multiplex network test again after modifying the configurations.
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MULTIPLEXING
Fault finding - Configuration
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Configuration screen
Make sure that the information displayed on the two tabs is correct.
The same configuration information for the two computers is essential for displaying the network topology.
Computer Multiplex network configurationConfiguration of computers that
can support fault finding
Injection PRESENT YES
ABS or ABS/ESP PRESENT YES
UCH PRESENT YES
Automatic gearbox connection PRESENT or ABSENT (option) YES or NO (option)
Instrument panel PRESENT YES
LPG PRESENT or ABSENT (option) YES or NO (option)
Steering lock PRESENT NO
Electric power-assisted steering PRESENT YES
Protection and Switching Unit PRESENT YES
Climate control (regulated) PRESENT or ABSENT (option) YES or NO (option)
Central Communication Unit* PRESENT or ABSENT (option) YES or NO (option)
Driving school unit PRESENT or ABSENT (option) NO (cannot support fault finding)
Airbag PRESENT YES
Automatic parking brake PRESENT or ABSENT (option) YES or NO (option)
Parking Distance Control** PRESENT or ABSENT (option) YES or NO (option)
Xenon bulbs ABSENT YES or NO (option)
Radio*** ABSENT YES
Multimedia interface*** PRESENT YES
*IMPORTANT:
NAV 4R ABSENT YES
ITS PRESENT YES
Others ABSENT NO

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MULTIPLEXING
Fault finding - Configuration
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Option: depending on equipment level
If during the multiplex network test the following message appears: No dialogue established with some computers:
check power supply and diagnostic lines before starting the test again.
–This does not prevent the multiplex network from being viewed.
–Check if too many computers have not been listed in the configuration: update the multiplex network according to
the table above. **Note:
The parking distance control is present on the multiplex network when it is fitted to the front and rear of the vehicle
(Vdiag OC only).
It is not present on the multiplex network if it is only fitted to the rear of the vehicle.
***Note:
The radio computers (which correspond to the LPN navigation) and the Multimedia Interface listed above must only
be configured with the LPN navigation (diagram version number = 04)

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MULTIPLEXING
Fault finding - Interpretation of faults
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MULTIPLEXING
Fault finding - Interpretation of faults
FAULTY SEGMENT ON THE MULTIPLEX NETWORK
NOTESFirst check that the computer at the end of the faulty segment is properly
powered (earth, + battery, + accessories or + after ignition).
Always check the computer conformity.
If the Protection and Switching Unit computer is not detected, apply the appropriate
fault finding procedure (see 87G, Engine Compartment Connection Unit, Fault
Finding Chart, ALP1).
IMPORTANT
The tool may not be able to pinpoint the faulty segment(s) exactly. It then suggests
several segments that could be faulty. In this event, repair the segment closest to the
diagnostic socket.
Isolate the faulty segment by disconnecting both ends of the segment. Check the condition of the connections (see
Technical Note 6015A Repairing electrical wiring, Multiplex: Multiplex network, Repair).
Check the continuity and insulation of the multiplex line H and multiplex line L lines between the two connectors
on the isolated segment.
Refer to the vehicle's multiplex network diagram for the allocation of tracks on the computers and connections.
Perform the necessary operations to check the continuity of the two lines (for example, replacing the wiring).
Make sure that the computer present in the vehicle is compatible with the Scénic II ph2 and that the signals it is
producing are correct.
Reconnect the segment.
Run the multiplex network test again using the diagnostic tool.
Is the segment still declared faulty?
NoEnd of fault finding.
Are there other faulty segments?
Yes
NoTest the multiplex network again to check the continuity and
insulation of the multiplex line H and multiplex line L lines
between the end of the faulty segment and the diagnostic
socket at connections 133B and 133C (see diagnostic
socket diagram).
Apply the same procedure to each segment.
Yes
AFTER REPAIRRun the multiplex network test again using the diagnostic tool.
Clear the stored faults on all the computers connected to the network.
Deal with any other faults.
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MULTIPLEXING
Fault finding - Interpretation of faults
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FAULTY COMPUTER
NOTES–Make sure the computers installed in the vehicle are the correct type and are
compatible with the Scénic II ph2.
–Check the power supply of the computers (earth, + battery, + accessories or + after
ignition).
Make sure that the computer wake-up mode is in full working order on the vehicle and properly assimilated by the
computers.
The wake-up mode is:
–timed power supply: UCH, instrument panel.
–+ accessories feed: Protection and Switching Unit, Heating and Air Conditioning System, Central
Communication Unit.
–+ After ignition feed: Injection, ABS/ESP, airbag, Electric Power-Assisted Steering, Automatic
Transmission, LPG/Natural Gas Fuel, Steering column lock, Driving School Unit, Automatic Parking
Brake, Parking Distance Control.
–+ After ignition + dipped headlights: Xenon bulbs.
IMPORTANT
Only establish dialogue with the discharge bulbs with + after ignition and the dipped headlights on.
–Switch to computer diagnostics mode.
Attempt to establish dialogue with computers.
●No dialogue from computers to diagnostic tool: see ALP 1
No dialogue with the computer or computers not communicating with the diagnostic tool.
Check the connections to the computers and that there are no open circuits.
If there is a repair procedure (see Technical Note 6015A, Repairing electrical wiring, wiring:
precautions for repairs), repair the connectors, otherwise change them.
●The computers only produce partial information when identified:
Check in the MR or World Vehicle Database to see that the computer really is compatible with the
Scénic II ph2.
Make sure the CLIP diagnostic tool update is recent enough to handle Scénic II ph2 faults.
If after these tests no faults or open or short circuits have been detected, contact your Techline.
AFTER REPAIRRun the multiplex network test again using the diagnostic tool.
Clear the stored faults on all the computers connected to the network.
Deal with any other faults.

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MULTIPLEXING
Fault finding - Interpretation of faults
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UNRECOGNISED COMPUTERS ON THE NETWORK
NOTES–Check the compatibility of the computers with the Scénic II ph2.
Make sure the CLIP diagnostic tool update is recent enough to handle Scénic II ph2 faults.
–Switch to computer diagnostics mode.
Attempt to establish dialogue with computers.
●No dialogue from computers to diagnostic tool: see ALP 1
No dialogue with the computer or computers not communicating with the diagnostic tool.
Check the connections to the computers and that there are no open circuits.
If there is a repair procedure (see Technical Note 6015A, Repairing electrical wiring, wiring:
precautions for repairs), repair the connectors, otherwise change them.
●Make sure that the computer identification information is correct and matches the vehicle in fault finding.
–Computer information:
–Vdiag:
–Program No.:
If no faults or open or short circuits have been detected after these checks, contact Techline.
AFTER REPAIRRun the multiplex network test again using the diagnostic tool.
Clear the stored faults on all the computers connected to the network.
Deal with any other faults.