ABS sensor resistance test

[downunderdave]

Hi folks,

Pass rear ABS sensor not working. The old one tested open circuit, but then so has the new replacement one. The new one fitted I still have the fault. Does anyone know what a working one would test as, as in ohms, or are they open circuit?

[5oclock]

A spare abs sensor I have tested open cct one way and 4.78 Meg ohms with the test leads reversed. Got a feeling that I had strange results ages ago when I was having a bit of drama with abs sensors. Had problems with replacement sensor being a bit different shape than the original when I changed front bearing hubs,and seem to remember that they are very sensitive to the distance to the tone wheel.Think the only way to be sure is to swap it and try it. Also the leads seemed pretty fragile so dont be tempted to pull on them. Also remember they are different to WG sensors, because I tried a WG one with the cable soldered up to the WH lead. Good luck, let us know how you go Dave.

[downunderdave]

Many thanks. I did not try reversing the leads. Now have done it. Yes, open one way. 3.783 Meg the other way, with 30 mins it has increased to 5.711. This is testing the old sensor I have taken out. The new one now installed has not fixed the problem. I did test the new one, but only one way, so only saw open circuit. Maybe I have a problem elsewhere with wiring or a module? Thank-you again for your help.

[Classic Boy]

Check the tone ring is still sound

[5oclock]

Just remembered, some brand new abs sensors from Rock Auto ,and they where rear ones also, were faulty and did not work.
So I had 1 bad abs sensor on the rear of WH. No worries I had already got brand new set front and rear from Rock Auto (dont recall what brand though). Swapped out the dud sensor but that didnt fix the problem. Bugger, must be the abs module, or wiring, or as Classic Boy pointed out could be tone ring or its position is moved a bit.So I spent a lot of time stuffing around because I thought the sensor was not the problem.WRONG!! I finally got 2 new rear abs sensors off ebay ,fitted them and all was good again.
I was using J Scan and it did show that the abs sensor was not giving the correct reading, but I got fooled because I had changed the dud sensor with new, and then changed that one again with the other new sensor and still had a problem. So I was fooled into thinking it was some other problem, but NO, just bad abs sensors!!
I think they are hall effect sensors(special type of transistor that is sensitive to magnetic fields) and can give all sorts of different readings on different multimeters. So just be warned. Unreliable checking them with the multi meter as well.
By the way the dud sensors from rock auto, the front one were good, just the rear ones were bad, and they were the same brand also.
Maybe get a couple of different brands from ebay.
OK, having reread my posts I may have given too much info....the bit about shape of sensors in the 1st reply was from a new set of front hubs, and the sensors that came with them were fine when used on those hubs but were a non standard shape and would not work with any other hub!!
The main point I was trying to explain was I changed out rear sensor with brand new TWICE and still no good, but it was both brand new sensors were no good!! So got more new rear sensors(different brand) from ebay and they worked fine. Still going fine years later. Hope I havent totally confused you mate. I do remember that the whole exercise with the bloody abs sensors was very annoying and confusing!!!!!
PS dont forget to let us know how you get on,,,good luck and dont trust anything!!

[downunderdave]

Hi guys, thank-you for your help. J Scan is immediately reporting a communication error with the sensor. I now know the sensor is good, so off to the auto-electrician I think, with a print out of the ABS pages from the service manual. I do have 2 more sensors coming from AliExpress, I might wait for them. Thank-you greatly again, Dave.

[5oclock]

If you swap the sensors that are on the Jeep over left to right and the fault shifts over, then it is 99% the sensor at fault. Might save a few hundred bucks at the auto place.