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i got a 03 svt that the front abs sensors aren't reading. the abs traction and brake lights are on, and on the scanner it shows that both front abs sensors aren't reading any help would be great! thanks
 

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you should see if your sensors are bad by tapping into them with a volt meter. if they aren't getting/sending the proper voltage then get new sensors.
 

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> on the scanner it shows that both front abs sensors aren't reading any help would be great! thanks

It seems odd that both would go out at the same time. I would check the wiring and connectors, particularly at the control unit.
 

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The Librarian
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You sure someone didn't just disconnect the sensors at their connectors up front?
(I know some have to kill the TC, though pulling the fuse is much easier)

You can turn the wheel, and look inside the fender well to see the connectors.
They're attached right....just a sec....lemme get a pic...
Here:
 

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C2H5OH
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you should see if your sensors are bad by tapping into them with a volt meter. if they aren't getting/sending the proper voltage then get new sensors.

Um, don't they output an AC wave and not a DC wave? In which case a DVOM would do no good.

Stick to using the scan tool.
 

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> DVOM would do no good.

I've never seen a DVOM that couldn't read AC as well as DC. Perhaps some that are made for auto use only do not, but most general purpose DVOMs have AC as well as DC.

That said, I believe they are inductive coils and their most likely failure mode would be an open circuit, which could be measured using a DVOM'a resistance function.


This might be of interest, even though it's probably not a Focus:

http://www.nichols.nu/tip608.htm

http://www.ohmcheck.com/abssensor.htm
 

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Um, don't they output an AC wave and not a DC wave? In which case a DVOM would do no good.

Stick to using the scan tool.

you my friend are wrong. i repair medical equipment and every single DVM or AVM that i have ever seen has both AC and DC capabilities.
 

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Resident Curmudgeon
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C2H5OH
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What I was eluding to is that the Wheel Speed Sensor outputs a square AC wave, which on a DVOM would just appear as on-off-on-off it wouldn't register as a voltage or a resistance that would provide any usable data.
To test them you need either a scope or a scan tool (though graphing DVOM would work too, but I doubt any of us have one of those).

That is far as I know.
 

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A square wave will register on an normal AC DVOM. The voltage reading may be off a bit, as the DVOM typically is calibrated to display the RMS voltage of a sinusoidal waveform. But a square wave would register.

I also suspect that with the sensor typically being an inductive device, the output is probably not that close to a square wave... square waves are not that easy to generate and typically one only sees a real square wave when an actively-powered switching device is used to generate it:

http://www.picoauto.com/tutorials/sensors-actuators.html

It seems abs sensors are closer to a triangular wave form.
 
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