My car is a Voyager 2003 2.5 crd
Since a few weeks my ABS sensor light is on permanently. Today I thought I'd test the sensors with a multimeter. I started with measuring ohms at both sensors at the rear, expecting to measure a resistance of a few hundred ohms. Both left and right sensor give an "infinite" reading. I think the odds are very small that both are defective. After consulting google, it seems to me that these sensors must be of the "active" type (as opposed to "inductive'). So next question is how to test these without a specialized scan tool. My multimeter has a mode "diode" that measures the turn-on voltage. It turns out one of the sensors does not give a reading on that so it is probably defective. So next step would be to order the part and plug it in. Is there something I am overlooking here? Any comments are welcome.

 

If I remember for my 2003 Voyager the new front sensor carried a resistance of around 30 ohms. Old one was open circuit.

 

Goggs, Thanks for that info. Meanwhile I found a post that confirms that these sensors are of the active type and difficult to test with a multimeter. (Diagnosing ABS -). I also have fitted a new sensor. Unfortunately this did not help. The ABS light is still on. So my initial approach has been to simplistic. I will need to do some more testing or bring the car to a professional.

 

Just to "humor me". If you slam the brakes on while moving, do you feel the ABS working?
I had an ABS light come on once and it read all kinds of code faults..Turned out to be a corroded/broken wire on the bottom of the under hood(bonnet) fuse panel!

 

Found my answer on "https://www.chryslerforum.com/forum/chrysler-voyager-town-country-21/g-voyager-2-8-crd-2005-abs-sensor-check-27487/". It took me a while to find this page because the forum does not let one search on short words such as -abs- while searching on -abs sensor- finds everything that matches either -abs- or -sensor-. The solution: do a literal search on "abs sensor" (note the quotes).
On topic: It turns out my passenger side sensor gives no signal.

 

Just had to get an OSF sensor for mines. £70 chrysler (none avaliable), £120 Eurocarparts, or £23 from Ebay.
We'll see if the £23 one lasts.

 

Just to add my 2p to this, I've had "TRAC OFF" illuminated for some time and thought I'd tracked it down to front left side wheel speed sensor. Replaced with one from ebay for around £25 too.

These are magnetic/induction type sensors, so yes when tested for continuity with meter you'll get a resistance If you get a dead short or open circuit and you've got a potential faulty.
To then test it's detecting rotation, put your meter on a low voltage setting (5v should be fine) then spin the wheel (Easiest is to use your wheel nut brace to spin it) and you should see a slight voltage generated.

When the sensors are totally disconnected (dead short or open) you'll get the BRAKE light illuminated constantly showing system fault (I drove with mine disconnected for a while waiting to replace it as managed to shear the bolt when removing it). Upon replacing the BRAKE went out but still TRAC OFF.
I got a scan done (Thanks @qinteq) and it showed my front RIGHT as potential fault now, so need to do the same tests myself and see if that one just needs the ring cleaning up (wire brushing should do it) or just replace the sensor itself.

 

You are welcome Andyb.

I've found that a worn old comb in a scutch[ing] hammer does a better job in a 1/10th of the time than any other cleaning device as its the bottom of the V bit not where people think the top that is counted.

 

Solved! Finally found time to replace the front right sensor. Abs light is now off. Thanks everyone.