Speedometer signal testing

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Speedometer signal testing

Postby Delva » Wed Jun 02, 2010 6:07 pm

I have a BMW F650 2003 ABS model, the speedo pickup is done by the rear ABS sensor. This signal I can meassure at the ABS sensor, but then it goes to 1)the ABS control untit (in thurn there is an output to the Speedo) 2)the Motronic and to the speedo.
Using the BMW testing equipment a signal has been sent, while disconnecting the ABS coupling and branching it to the test equipment, bu no reaction was seen at the speedo.
The electronic printed plate of the speedo has been replaced.
The wiring does not show any defect.
The ABS sensor is working.
How can I branch the picoscope for motorcycles (version 6) knnwing there are 3 wires comming in and what measusring parameters should I use to be able to vieuw the signal ?
Once I know this then I can start measuring and find where the signal stops.
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Re: Speedometer signal testing

Postby Matt Fanslow » Wed Jun 02, 2010 8:49 pm

Just so we are clear, you wish to scope the communication lines between modules to ascertain where the VSS information is being lost?

Thanks.
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Re: Speedometer signal testing

Postby Guest » Fri Jun 04, 2010 6:08 pm

[quote="Matt Fanslow"]Just so we are clear, you wish to scope the communication lines between modules to ascertain where the VSS information is being lost?

Thanks.[/quote]
Yes I know the signal is arriving at the ABS module, but here the signal changes to drive the speedo.
But I have no idea what kind of signal (V, timescale,..) will be arriving at the speedo from the ABS module.
Just having bought the automotive motorcycle pico 6, I have no experiance in the setting to be used in this case.
Once I know this I can see what is comming in on the 2 wires going to the speedo.
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Re: Speedometer signal testing

Postby Matt Fanslow » Fri Jun 04, 2010 7:29 pm

You will not be able to derive the information you seek by scoping communication lines. You will require a scan tool that can communicate with all the modules involved.

If power and ground are at the module not displaying vehicle speed and the communication lines are active (a clue would be other functions of that module using information from other module sent via bussed info working normally) then I would be suspecting the module.

Assuming this is just a failed module, do you have the proper scan tool to code and program the module in question? Keep in mind, many of the tools may require you bring up the firmware level of the entire vehicle which could translate into a lengthy program time.
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Re: Speedometer signal testing

Postby autosparky » Sat Jun 05, 2010 9:37 pm

I don't think you can scope as already mentioned, and a scan tool is the only diagnostic tool in this case, but I will add you may need to get the instrument cluster coded for the vehicle if the circuit board has been replaced, there are very few after market tools that can do this so you may want to give the dealer a call
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Re: Speedometer signal testing

Postby IanCrane » Thu Aug 19, 2010 9:34 am

We are looking at CAN bus are we?
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