how to connect an oscilloscope to monitor ABS sensor output ?

Question

I would like some advice as to how to connect an oscilloscope to an Audi 90 quattro in order to check out the ABS sensor outputs. I have located the multiple connector under the rear seat and identified the wires associated with each wheel sensor.

I'm not sure how to connect the oscilloscope leads -

a) into the unplugged connector ?

b) leave the connector in place and connect into the wires before the connector ?

c) if the connector is left in place, should the ignition be left 'on' or 'off' ?

d) there are two connectors for each wheel sensor, should the scope lead and its ground wire be connected across the two connectors ?

Any advice greatly appreciated,

Regards,

Bob

JPF · Accepted Answer

What are you trying to achieve?

the rogue · Answer

You need to plug the ground of the scope to any grounded part of your vehicle......turn on the ignition......Jack up the wheel you want to test so it's off the ground....

Plug the test lead of the scope to any one of the two wires comming from your abs wheel sensor and then turn the wheel.......one of the two leads coming from the sensor will give you a higher signal than the other....and what you should see is a nice square wave that changes frequency with wheel speed.....

There....that should help!

The Rogue

Bob · Answer

Thanks,I'll try this and see if I can find out what is happenning at the wheelsensor output.I had been previously connecting the oscilloscope leads across the twosensor wires...Thanks for your help.Regards,            Bob

JPF · Answer

Which is the only way to read the sensors output.  Two wires out, A/Cvoltage and frequency.  Once again, what are you trying to achieve?

how to connect an oscilloscope to monitor ABS sensor output ?

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