CAN – Multiplexing Worksheet

1.0 CAN Waveform on Oscilloscope

1.1 Locate the Range Rover or other suitable vehicle with easily accessible CAN system twisted wires. Which vehicle do you have? (Year, make and model) _2003 land rover ___________________________________________________

1.2 Locate a twisted wire pair. Describe where the wires are located: by the ABS TCS ECU ____________________________________________________

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1.3 Record the waveform of one of the wires below: (Make sure your time is small enough so you don’t have “aliasing”.)

I

Colour of wire: yel br ……………………………………

Time per division: …200ms………………………………

Voltage per division: ………1v……………………..

1.4 Record the waveform of the other wire in the twisted pair.

Colour of wire: yel black……………………………………

Time per division: …200ms………………………………

Voltage per division: ………1v……………………..

1.5 What is aliasing? Describe it.

Aliasing is the distornion of readings on a osilloscope ______________________________________________________________

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1.6 How do you know these waveforms are not “aliasing”?

Because the is no distortion and they are clear and easy to read

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1.7 In the 1.3 waveform above, what is the main voltage on the line?

2.3v …………

What is the other voltage on the line, when the voltage is pulled up or down to “talk” ?

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1.8 In the 1.4 waveform above, what is the main voltage on the line?

…0.25v…….

What is the voltage on the line, when the voltage is pulled up or down to “talk”?

……….

1.9 Observe the signals in 1.3 and 1.4 above with a voltmeter. Compare it with DC volts or AC volts setting. Which setting would tell you if the signal is switching. Explain:

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a DC waveform would tell us if the componet was switchin by flatlining when not switching and then jump when switching then flat lining the top of the jump till the switch is turned off.

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2.0 Scan Tool Observations

2.1 Find a vehicle that will show CAN system operation on a scan tool (such as the Range Rover.

Which vehicle are you using? Land rover 2003……………………………………………..…

Which scan tool are you using? Autoboss star……………………………………………..

2.2 What different functions are available on the scan tool to examine the CAN system?

_print, portrait, landscape, demo, quickscan and manual scan __________________________________________________

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2.3 List the different systems that are controlled by CAN? (note which are high speed and which are low speed)

ABS, ESP, TCS high speed_________________________________

EHC electronic ride level_________________________________

EDC electronic damper control_________________________________

MRS multiple restraint systems_________________________________

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3.0 Wiring Diagram Exercise

3.1 Locate a wiring diagram for a CAN system (hopefully one you can investigate or work on.) i've got a MOPAR 1973 man CAN wiring diagram

3.2 Describe the type of wiring diagram this is?

Both central and engine CAN diagram

3.3 Show the high speed system parts of the diagram.

Red = high speed systems of the diagram

4. Show the low speed parts of the system on the diagram.

   Black = the low speed systems

   3.5..Show the location of a “Gateway” on the diagram.

Blue = gateway

6. Show where the system could be “divided” to aide in diagnosis.

Green is the division line

7. Describe how this is helpful in diagnosis:

   it limits what you are testing with the scan tool and limits down the fault finding proc

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3.8 Locate a system that goes to “sleep” after a short time. What is it?

Pink is the sleeping system.

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3.9 What voltage do you see when it is “awake”? …12 volts………………………

What voltage do you see when it is “asleep”? ……0……………………

On what wire do you see this voltage change? ………the switch wire C538 …………………

3.10 Amp Drain:

Measure the amp drain at the battery when the system is asleep ……..

Measure the amp drain at the battery when the system is awake: ……..

How long did it take the system to go to sleep? …………

What made the system “wake up”? ……………………………………….