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2005 Chrysler Town & Country 3.8 Wheel Speed RF Input Signal Missing

  • MOROSO321
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02 Sep 2019 09:30 #33353 by MOROSO321
Here is my dilemma with this vehicle. I have checked both sides right front and left front of vehicle. The abs sensors show good feed. 12 volts. wire color is dark green/violet is 12 volt supply and my signal wire is dark green/white.
One of the problems is that when I disconnected the abs sensor to check fo ohms, I don't get a reading until I place the meter on 2m ohms resistance. and I believe the spec for this is 450 to 2200 ohms. I did not get a reading on both sides when I disconnected the sensors.

Secondly, I place the meter on volts to check an rpm signal on both sides and I did not get any readings. Maybe I didn't hook up my meter leads the proper way. I lead to ground, and the other lead to the signal wire of the sensor. I spun the wheel and didn't get nothing. no reading. Can someone tell me the hook up for a modus using lab scope. i want to use the scope but i don't think i'm doing it now because i'm not getting anything.
i don't know where to go from here. I can't get an ohm reading and i can't read an rpm signal when spinning the tire. Need some guidance.

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  • Tyler
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02 Sep 2019 10:11 #33354 by Tyler

One of the problems is that when I disconnected the abs sensor to check fo ohms, I don't get a reading until I place the meter on 2m ohms resistance. and I believe the spec for this is 450 to 2200 ohms. I did not get a reading on both sides when I disconnected the sensors.


If these are digital sensors, and they sure look like it from the wiring diagram, then you'll never get a good resistance reading. Failed sensors AND good sensors will both show open or close to it. :silly:

Secondly, I place the meter on volts to check an rpm signal on both sides and I did not get any readings. Maybe I didn't hook up my meter leads the proper way. I lead to ground, and the other lead to the signal wire of the sensor. I spun the wheel and didn't get nothing. no reading.


FYI, Chrysler used two different types of 'digital' speed sensors on their cars around this time. Wiring is identical, but function is different. The first type (the earlier type, in my experience) used 12V on a supply line, and generated a .8 to 1.6V signal on the other.

The second has a 12V supply line on one, and a steady ground on the other. This design is deceptive, because the 12V supply and signal are the same circuit. ;) Because you said you saw no signal on the LF, I'm gonna guess you have the second type.

I'd suggest looking at the LF first, for a known good reference. Connect to the 12V supply wire, and scope ground wherever you can. 20V scale, one or two second time. Spin the wheel and look for 400mV dips in the 12V line. OR, use AC coupling and a one or two volt scale. Again, you're looking for 400mV square waves.

Technically, the signal from these sensors is current, and not voltage. ;) 7 to 14 mA, specifically. The voltage change you see on the scope is actually a result of changing current flow. But, measuring the current on these sensors is a huge pain, and the voltage method has never failed me.

This SD video goes through the whole process:

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02 Sep 2019 15:01 #33361 by MOROSO321
yes tyler, i have a steady 0.00v on the signal wire. which is the dark green/white.
I have the latter setup on this vehicle.

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