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

Electrical equipment
"The repair procedures given by the manufacturer in this document are based on the
technical specifications current when it was prepared.
The procedures may be modified as a result of changes introduced by the
manufacturer in the production of the various component units and accessories from
which his vehicles are constructed."
V4
All rights reserved by Renault s.a.s.
Edition Anglaise
Copying or translating, in part or in full, of this document or use of the service part
reference numbering system is forbidden without the prior written authority of
Renault s.a.s.
© Renault s.a.s.
V4 MR-372-J84-88B050$000_engTOC.mif
MULTIPLEXING
Fault finding - Introduction 88B - 2
Fault finding - List and location of components 88B - 6
Fault finding - Operating diagram 88B - 7
Fault finding - Features 88B - 8
Fault finding - Defect and safe modes 88B - 10
Fault finding - Configuration 88B - 11
Fault finding - Interpretation of faults 88B - 14
Fault finding - Customer complaints 88B - 19
Fault finding - Fault Finding Chart 88B - 20
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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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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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Fault finding - Introduction
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COMPUTERS
–Valid: green border, green lettering.
–Not detected: red border, red lettering.
–Do not support fault finding: black border, black lettering.
–Not recognised: red border, red lettering + exclamation mark.
SEGMENTS
–Valid: green dash.
–Faulty: red dash.
–Cannot support fault finding: black dash.
INTERPRETING TEST RESULT CHARTS
On the Problems tab, the computers are organised into the following groups:
–Not detected if the computer failed to respond to the tool's identification request.
–Within the not detected category, the computers are subdivided into Stores multiplex network configuration
and Does not store multiplex network configuration.
–Not recognised if the computer is detected but cannot be identified from its response.
On the Information tab, the computers are organised and listed as follows:
–Cannot support fault finding, if the computer cannot support fault finding with the tool and therefore was not
queried.
–Valid if the computer responded correctly to the tool's request.
If the Proceed icon in the bottom right-hand corner is selected, a new screen will appear with the following tab:
Under the Results tab the computers are organised into the following groups:
–Faulty if the computer is recognised and has a non-zero number of faults.
–OK if the computer was detected, recognised and has no faults.
–Not recognised if the computer was detected but could not be identified from its response.
–Not detected if the computer can support fault finding but failed to respond.
FUNCTION TESTING
The vehicle function tests screen resembles the multiplex network test screen in showing a diagram of the network
architecture if this is known and displayed.
The Function tab displays the various computers involved in the functions whether distributed or not distributed over
the various computers.
The Info tab displays the other possible functions found on the vehicle concerned.
Selecting a function from the list greys out the computers on the diagram that are not involved in that function.
The Fault finding button runs fault finding on the function selected from the list.

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Fault finding - Introduction
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REPAIR HELP:
●Assistance with computer or faulty segment detection:
If the multiplex network is completely frozen, this command can isolate multiplex network segments and thereby
rule out those that respond correctly to the tool. This makes it easier to pinpoint the cause of the fault.
The algorithm for help with locating faults is intended for dealing with electrical faults present solely on the multiplex
line; it is therefore essential that connectors and computers not attached to the bus are not taken into consideration.
●A test for multiplex network faults by using physical measurements:
When a multiplex network segment has a short circuit, the computers can no longer communicate with each other or
using the diagnostic tool. At this point, the network test is not operational.
The CLIP tool can identify several types of faults by taking electrical measurements on the multiplex line H and
multiplex line L multiplex network. It can detect a multiplex line L/multiplex line H short circuit, a multiplex line
L/+ 12 V short circuit, a multiplex line H/+ 12 V short circuit, and a multiplex line H/earth short circuit.
Then, by disconnecting the connectors and computers in the order described under the "Help with detecting faulty
segments - computers" heading, identify the actual or possible segment causing the multiplex network fault.

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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.
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Fault finding - Operating diagram
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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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Fault finding - Features
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MULTIPLEXING
Fault finding - Features
To improve the performances of vehicles, more
computers are needed to share more information in
order to achieve optimal operation.
With multiplexing, numerous signals can be sent from
one computer to several others via a single electrical
connection.
Solution without multiplexing
Example: each computer would have to have its own
electrical connection to deal with vehicle speed signals
coming from the ABS. The number of connections
increases when there are more signals to be
communicated.Solution with multiplexing
In this instance, the vehicle speed signal is distributed
from the ABS computer to as many computers as
require it on a single electrical connection. All other
signals are transmitted via this connection as well.
Thus there is only one connection regardless of the
number of signals to be exchanged.
Advantages of multiplexing
●Reduction in costs as there is a reduction in
wire length and there are fewer connectors.
●Less wiring,
●Increased reliability due to there being fewer
connectors.
●Easier to locate a faulty component in some
cases.
Multiplex operation
The operation of a multiplex network can be compared
to an underground line which transports a number of
passengers. All the passengers use the same line
even though they get on and off at different points and
they take different trains depending on when they
started their journeys.
The multiplex network operates in a very similar way.
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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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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