airbag RENAULT SCENIC 2008 J84 / 2.G Electrical Equipment - Multiplexing Workshop Manual

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MULTIPLEXING
Fault finding - Introduction
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188BMULTIPLEXING
Fault finding - Introduction
INTRODUCTION
Description of the multiplex network:
The multiplex network consists of a twisted pair of wires connected to several vehicle computers. These two wires
are called multiplex line H and multiplex line L.
Two of the computers have an internal resistance of 120 Ω (terminating resistance):
–the airbag computer,
–the injection computer:
The network carries data exchanged by the computers.
The Scénic II ph2 is a new generation multiplex vehicle; the main change is the increase in communication speed
to 500 kBauds.
On the Scénic II ph2, fault finding can only be performed on one multiplex network with the RENAULT tool.
The maximum number of computers on this network is 15.
PURPOSE
●The purpose of the multiplex network test is to determine the various computers present on the vehicle's
multiplex network, as well as the cause of possible inter-computer communication faults.
●It also serves to determine the functions installed in the vehicle, which are sometimes housed in various
computers (distributed functions).
●The test also checks the condition of multiplex network segments.
●The multiplex network test can also run fault finding on computers disconnected from the multiplex network;
this provides an overview of the vehicle's electronic layout. IMPORTANT
Fault finding can only be carried out on Scénic II ph2 using the CLIP diagnostic tool equipped with the new
vehicle connection probe cord (Part no.: Elé 1674 or 00 00 167 400).
Note:
A second multiplex network for the navigation system may also be present.
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MULTIPLEXING
Fault finding - Introduction
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MULTIPLEX NETWORK OPERATION TEST
This step is the essential starting point for any computer fault finding procedure.
It ensures that the network is correctly connected at the terminals of each computer and that the signal is correctly
sent to it and received by it. On the Scénic II ph2, this function also reads the number of faults present on the
computers.
The multiplex network test function is executed automatically after vehicle selection by the user.
After the network check, the other functions become accessible.
MULTIPLEX NETWORK TEST PROCEDURE
–Establish dialogue with the computers storing the vehicle configuration (read identification).
–Vehicle configuration read on the two computers that hold the multiplex network configuration (airbag and UCH
on the SCENIC II ph2).
–List of computers that can support fault finding read from the two computers that hold the multiplex network
configuration.
–Computer interrogation.
–Physical (electronic) measurements on the multiplex line network. Vehicle computer power supply for fault finding:
insert the vehicle card in the card reader.
Press and hold (over 5 seconds) the Start button in the absence of start conditions (for example: selecting a gear).
Connect the diagnostic tool and perform the required operations.
IMPORTANT
To supply the discharge bulb computer, switch on the dipped headlights.

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MULTIPLEXING
Fault finding - Introduction
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MULTIPLEXING
Multiplexing enables signals to be sent between different computers on the vehicle, such as:
1UPC.
2Injection computer.
3BVA computer.
4LPG or CNG computer.
5ABS/ESP computer.
6UCH.
7Electric steering column lock.
8Automatic parking brake computer.
9Parking distance control computer (depending on version).
10 Electric power-assisted steering system.
11 Instrument panel.
12 Diagnostic socket.
13 ITS or Multimedia interface unit (depending on version).
14 Climate control computer.
15 Driving school unit (depending on vehicle).
16 Airbag/pretensioner computer.
MR-372-J84-88B050$200_eng.mif

MULTIPLEXING
Fault finding - Operating diagram
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MULTIPLEXING
Fault finding - Operating diagram
1UPC.
2Injection computer.
3BVA computer.
4LPG or CNG computer.
5ABS/ESP computer.
6UCH.
7Electric steering column lock.
8Automatic parking brake computer.
9Parking distance control computer (depending on
version).
10Electric power-assisted steering system.
11Instrument panel.
12Diagnostic socket.
13ITS or Multimedia interface unit (depending on
version).
14Climate control computer.
15Driving school unit (depending on vehicle).
16Airbag/pretensioner computer.
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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.

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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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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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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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MULTIPLEX NETWORK NOT OPERATIONAL
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.
IMPORTANT
Switch off the ignition or remove the RENAULT card from the card reader, check that
the side lights are off and wait for 1 minute.
Finding the fault
type
NOTESUse the diagram of the multiplex network of the vehicle
(diagram of the diagnostic socket).
Measure the resistance between connections 133B and 133C on the diagnostic socket.
What is the resistance?
0 ΩΩ Ω ΩThe two lines are in short circuit (see Introduction: Repair advice).
Check that there is earth, + battery feed, + accessories feed or + after ignition feed
at the airbag computer and UCH terminals. To allocate the connections on the
computers and connections, use the vehicle diagrams for the airbag computer (756)
and the UCH (645).
For each 133B and 133C connection between the different vehicle computers, check
there is no interference resistance and no short circuit to earth or to the + battery feed.
60 ΩΩ Ω Ω
± 10 ΩΩ Ω Ω
Between 70 ΩΩ Ω Ω

and 110 ΩΩ Ω Ω
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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MULTIPLEX NETWORK NOT OPERATIONAL (CONTINUED)
120 ΩΩ Ω Ω
± 10 Ω
Open circuit on one or two lines.
Disconnect the airbag and check connections 133B and 133C between the diagnostic
socket (225) and the airbag (756).
Is the multiplex connection correct?
YESCheck that the resistance is approximately 120 ΩΩ Ω Ω
± 10 Ω
between the two network connections on the airbag computer:
–If the resistance is not approximately 120 ΩΩ Ω Ω
± 10 Ω, contact
Techline.
–If the resistance is 120 ΩΩ Ω Ω
± 10 Ω, check the continuity and
absence of interference resistance of connections 133B
and 133C between the diagnostic socket (225) and the UCH
(645).
If there is a repair procedure (See Technical Note 6015A,
Repairing electrical wiring, Multiplex: Multiplex
network, Repair).
Check that the resistance is approximately 120 ΩΩ Ω Ω
between the
two network connections on the UCH computer:
–If the resistance is not approximately 120 ΩΩ Ω Ω
, contact
Techline.
Repair the multiplex connection between the diagnostic socket
and the airbag.
If there is a repair procedure (See Technical Note 6015A,
Repairing electrical wiring, Multiplex: Multiplex network,
Repair).
If the fault is still present, contact your Techline.
NO
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.