Focus Fanatics Forum banner

ABS sensor test with meter?

51K views 21 replies 8 participants last post by  carlos1984 
#1 ·
My Haynes manual states I can check my ABS sensors with a volt meter by connecting the meter, reading VAC and spinning the wheel. Either this is bogus or I have 4 bad sensor/wheel bearings.

I recently replaced all 4 wheel bearings and I have the ABS light. See other post.

http://www.focusfanatics.com/forum/showthread.php?t=212910

Thanks for any info

Vincent
 
#3 ·
I don't know the exact speed I was spinning, but it was by hand and pretty fast. The meter didn't budge. I tried the left front which is a new bearing (black ring inboard towards sensor) and on the right rear wheel which the bearing and hub was purchased preassembled from Ford (Trousley). Spinning by hand with the wheel installed as fast as I can and the meter didn't change.

If I read for ohms across the sensor, I only get a reading if I put the probes on a particular way, almost like it is a diode.

The ABS light wasn't on before I started the project. I removed/inspected all 4 sensors, installed, no visual damage. I checked all 4 connectors, connected.
I drove the vehicle after replacement. I tried disconnecting the battery before, but it didn't didn't reset. I tried again tonight, but nothing.

Vincent
 
#4 ·
Send me your OHM readings. Do you have traction control? They use a different kind of sensor that will not produce voltage readings. pm me and I will try to help.
 
#7 ·
The car does not have traction control.

The front wheel sensors read 3.625mohms/3.680mohms. I don't remember what the rears were and I just cleaned up for the night (frustrated) [rant].

I will check the rears tomorrow.

Again, I am only able to ohm the sensor if I have the test leads oriented one direction. If you reverse the leads, it reads open.

Thanks for the help.

Vincent

Oh, the front bearings were CFM but Ford OEM. The 2nd set of front I have to install were purchased from Trousley and are the same exact ones. I checked the black ring and it has a slight magnetic field. I removed the driver's side sensor and placed a ferrous tool (Snap on pick) and the wheel sensor ring pulls at the pick.
 
#8 ·
Hall-effect sensors can't be tested the same way the older-technology tone-ring (relucator) and coil systems can be tested with a volt meter. I get zero volts on my voltmeter from all four of my ZTS's sensors while spinning the wheels (fast) (w ABS & traction) and both systems work fine.
 
#9 ·
Well, it also depends on the sensitivity of your meter. What AC range is it set to?

And, as someone said, if it is a hall effect sensor, rather than an inductive pickup type, the AC voltmeter test probably will not work.

I don't know which type the Focus uses, hall effect or inductive coil.
 
#10 ·
At Ford, we refer to them as Active and Passive. Passive sensors are tested with an OHM meter and can be tested to see if they produce AC voltave (in milivolts) and Active require a 12V power source and are tested in AMPS. Your meter has to be wired in series with the negitive lead from the sensor to the module and the positive wire has to be complete with the key on. The signal should toggle from 7mA to 14mA. If you are in Charlotte NC week after next, I am teaching Advanced Brakes.
 
#11 ·
"What AC range is it set to?" Actually I went to an oscilloscope at 10millivolts/div and saw nothing. I later verified that I have hall-effect sensors.

A measurement of the current through a hall-effect sensor is required to verify functionality.
 
#12 ·
The meter was set to auto range and it saw nothing. I tried to check the amps, but nothing there either. I have a two standard Fluke Meters (model 77 and 87).

I think I have resolved my original problem though, I forgot to swap over the rear ABS rings when I installed the new hubs. I thought they came with them.

Still, it would be nice to figure out how to test individual wheel sensors with a simple meter if possible. I have access to a scope and I may give it a try as well.

thanks,
Vincent
 
#14 ·
Hey Guys, adding to my rep points will not hurt my feelings. LOL I sent you guys that requested the pinpoint test an email copy. I did find out that the pictures will not show up BUT if you have a fax machine, I will be happy to print it out and fax it to you. Thanks guys, I hope this helps.
 
#15 ·
a meter will not work to test a sensor, it can tell you if the coil is bad with ohms, but to test the sensor and tone wheel you need to have an osciliscope. it will show you the wave patern and any hickup in that will be shown on the screen. it switches back and fourth too fast for a meter to pick up.
 
#16 ·
You can use a meter for the active sensor, an AMMETER. It is acurite enough to test the sensor and the tone ring, you just have to go very slow. HOWEVER, an osciliscope would but the best and most perfered method. But not everyone has one they can use and it is for more likely that you can get a meter. Besides, at the dealer and here in the classroom, we use the multimeter.
 
#17 ·
Thanks for the info and help. I need to get an o-scope and check it out when I get the car back together. I ordered the tone ring today ($30).

Also, I added to your rep, but it hasn't shown up. Won't let me add to it again.

Thanks,
Vincent
 
#21 ·
Well, the tone ring came in today and I removed the rear hub and installed in about 20 min. I pulled the battery cable while I changed, and when I started the car up the ABS light was still on. However, after driving 50 ft or so (hitting 12mph I think), the ABS light went out.

Drove the car around the block and no lights. What a goober mistake. Cost me 2 weeks of time, about an extra $120 in parts (of course I have a new front bearing in a box if I need) and my pride. My wife congratulated me on a new record. Almost a month to complete a car repair. I just asked her when was the last time she came out in the garage other than to bust my chops. Then said, yea, it is difficult to make it into the garage with the couch stuck to her @$$. She hasn't said anything to me in an hour or so.

Thanks again for the advice and moral support.

Now I get the thing aligned tomorrow.

Vincent
 
#22 ·
hi boating fool Im having the same problem with my 2002 zx5, i took it to a garage because my rear right bearing was damage and it was so bad that it damaged the cylinder letting all my break fluid out, I bought all the parts nesseccary inclubing the abs ring that was damaged. after I turned it on the abs light was on the mechanic told me the light would go away after i drove it. But it didnt took it back and he told me it could be another sensor, but he didnt have the equipment to test it.
Anyways could you tell me where the tone ring is located, as I believe the problem has something to do with the right rear because it wasnt there prior to the repair.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top