Controller Area Network ( CAN ) is an international standard
for serial communication used to control devices on a network.
Range Rover 2001
It is easy to identify the wiring as it is just a twisted pair of thin
wires. These will be found all over the vehicle - sometimes in
with a conventional main loom. The wires are called 'CAN High'
and 'CAN Low' and it is important that any interface is connected
correctly to these wires.
Because the magnetic field around a wire is circular and perpendicular to the wire, an easy way to amplify the wire's magnetic field is to coil the wire, as shown below:
The current passes along the wires creating a magnetic field; this energy is easily transferred from one system to another thanks to a method that is
similar to the windings in a transformer.
If different cable groups are running parallel between 2 or more components, then separating them will reduce the interference transferred from one to the other. If cable groups need to cross over each other, try to ensure that they do so at 90°. However, Better still, twist the send and return wires together and the net magnetic flux through adjacent turns will cancel each other (provided the twists are even); it will also even out the charge on the wires if subject to an electric field. The intention of this is to reduce the interference between the lines. The tighter the twists the better.
ABS Control Unit
Oscilloscope which I have used, model-"Seintek S2800"
Taxi Meters require a speed pulse signal in order to calculate the fare.
Hence on CAN Bus equipped vehicles, a CAN Bus Speed Pulse Interface
will be required.
Chenal A-colour of wire is yelow and brown
Voltage-2V per division
Time-50us per division
Measured voltage Chenal A:
Oscilloscope-2.63V
Multimeter-2.37V DC
Chenal B-colour of wire is yelow and black
Voltage -2V per division
Time-50us per division
Measured voltge Chenal B:
Multimeter-2.65V DC
CAN (Controller Area Network) it is an international standard for serial
Communication used to control devices on a network. The CAN standard
governs some of the physical attributes of the network as well as the low
level software communication protocols. Physically the CAN bus itself
consists of a twisted pair of wires which use differential voltages for data
Transmission. CAN is designed primarily for control and hence the messages
used are small (8 bytes max).
The basic message structure contains two parts: a message identity and
message data. The actual structure is a little more complicated than this,
with error detection, synchronization and other bitsbeing embedded into
each message. However one of the great benefits of CAN is that the chips
used take care of these details for you and provide you simply with message
and data information.
Most of the higher specification GPS Navigation systems will require a speed
pulse signal as a minimum. Many also have inputs for illumination and reverse
signals. On CAN Bus vehicles these signals may not be present so a CAN Bus
Interface will be required.
The reasons for the vehicle manufacturers using CAN Bus are:
1. Significant reduction in wiring leading to:-
a) Significant reduction in manufacturing cost and hence retail cost.
b) Reduction in weight resulting in improved fuel consumption.
2. Reduced number of interconnections hence improving reliability.
I've understood the basic principles behind CAN the next question is
‘exactly how is the basic message structure used to communicate all
this information?’. Here is a key difficulty of CAN. Whilst the general
CAN methodology, the electrical connections, packet structure, error
correction and low level software are specified, the rest is left up to me.
In practice this has meant that every automotive manufacturer has chosen
their own proprietary protocols. Massey Ferguson will be different to Audi
will be different to BMW etc. The reason for this is probably two fold: firstly
automotive companies don’t want unauthorized people tapping into the bus
that manages all the safety critical electronic devices in the vehicle, and
secondly diagnostic equipment and training are valuable revenues streams.
For saving the battery power in this car I've found the sleep mode operation.
When an ignition is off, electronic system goes to "sleep" after a short time.
Checking voltages on CAN-and CAN+ to see when bus is "alive" and "down"
The wire is yellow -brown on the ABS Control Unit
1. Voltage, when system in "awake" - 0.29V
2. Voltage, when system in "asleep" - 0.12V
3. When system in "awake" the battery used - 2.35Amps.
4. When system in "asleep" The battey used - 0.92Amps.
I've used bonnet switch and meaured different at 5 minutes later
*To prevent excess parasitic drain when key is off, a sleep protocol is used
*Not all modules are connected to ignition and see "Ignition off"
*The bus can't go into sleep mode untill all the modules have said
"ready to sleep"
*Any module can transmit a message to "wake up" or become "active"
or "alive".
* When the bus goes to sleep, some modules may still be active( such as
door module for key entry or cabin compartment module)
*Voltage of CAN B-should tell you if it's in sleep mode
*With key off, modules a sleep, internal connections
*Beware ignition switch withj poor connections:and transceivers shut
down, bus circuit is open
Causes conflicting messages to be sent around the bus and they get
all confusing.
some reasonable explanations, i like how you have put the information you have found from other sources in different colours, but you also need to say were you got it from
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