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If I plug in a working abs sensor, will the light go out?



len_beach

ClioSport Club Member
  E92 M3,172 track car
I have an abs light on which has been diagnosed as an open circuit on the drivers side rear.

Ive taken a punt on a used stub axle and abs sensor for £30 rather than a new Renault sensor for £125. If I simply plug the new sensor in without fitting the stub axle, will the light extinguish or does the senso have to take a reading from the abs ring?
 

len_beach

ClioSport Club Member
  E92 M3,172 track car
It was diagnosed on clip by Doncaster Diagnostic Centre as an open circuit Sam. I could be a broken wire but I thought changing the sensor would be a quick option as I am fitting camber shims anyway.
 
  Mk4 Mondeo Estate
An open circuit is what it says it is, a break somewhere in the circuit so you are taking a 50/50 chance on it being the sensor.
 

DaveDreads

aka Philomena Cunk aka Barry Shitpeas
ClioSport Club Member
  172, E46 320D, Golf
I had a knackered ABS sensor years ago that originally caused my SERV/ABS/TC lights,
it was replaced but i've had the damn thing reappear every now and again ever since,
no amount of diagnostic checks can find the problem, there are no fault codes on mine at all.

But yet it remains and will randomly show up now and again untill the engine's turned off,
then months can go by and I wont see it, then it'll show up to say hello again.
 

len_beach

ClioSport Club Member
  E92 M3,172 track car
An open circuit is what it says it is, a break somewhere in the circuit so you are taking a 50/50 chance on it being the sensor.
I appreciate that but it could be break in the cable running over the rear beam and I thought as I'm fitting the shims I may as well swap it.
 
  Mk4 Mondeo Estate
You should actually diagnose the fault rather than just chucking parts at it though mate. If you've got a multimeter disconnect the sensor and run a magnet backwards and forwards across the sensor, if you get a fluctuation the sensor is more than likely good.
 

len_beach

ClioSport Club Member
  E92 M3,172 track car
You should actually diagnose the fault rather than just chucking parts at it though mate. If you've got a multimeter disconnect the sensor and run a magnet backwards and forwards across the sensor, if you get a fluctuation the sensor is more than likely good.
I know it's not the ideal solution. The problem with the rear abs sensor is you have to remove stub axle to get the sensor off.

I have a multimeter and may be able to squeeze a magnet in above the abs ring. Will any size magne work even if it's really thin?
 
  Mk4 Mondeo Estate
The bigger the magnet the better. You could also just spin the wheel but bear in mind that if you don't get any fluctuation it could be the pole wheel rather than the sensor (unlikely due to open circuit)
 

len_beach

ClioSport Club Member
  E92 M3,172 track car
The bigger the magnet the better. You could also just spin the wheel but bear in mind that if you don't get any fluctuation it could be the pole wheel rather than the sensor (unlikely due to open circuit)
Thanks Owen. I'll test the process on the replacement sensor and see how the sensor fitted reacts.

So I'm just testing for a current? I'm pants with electrics.
 
  Mk4 Mondeo Estate
I believe you are actually testing for voltage (I'm not over ally great with electrics so trying to remember what we were told at college) but you could always try both.
 

len_beach

ClioSport Club Member
  E92 M3,172 track car
I believe you are actually testing for voltage (I'm not over ally great with electrics so trying to remember what we were told at college) but you could always try both.
Magic. I'll give it a whirl. Thanks Owen.
 

len_beach

ClioSport Club Member
  E92 M3,172 track car
Right, I tested the o/s abs sensor today along with the n/s and the replacement sensor.

I used a multimeter and a small magnet waved across.

The suspected dicky sensor showed a reading of 0.3 to 0.4 (I can't remember what setting I had the multi-meter on).

The suspected working sensor showed 3.4-3.5.

The assumed working replacement showed up to 4.9 howeve I could get the magnet much closer to the reading face with this.

Now I'm guessing this means the sensor is the issue?
 
  Mk4 Mondeo Estate
That would say its a sensor fault to me. It looks like you had that on volts which in general (don't know specs for Renault) would be in tolerance for the the good sensor.
 

len_beach

ClioSport Club Member
  E92 M3,172 track car
That would say its a sensor fault to me. It looks like you had that on volts which in general (don't know specs for Renault) would be in tolerance for the the good sensor.
It was volts Owen. I tested on the replacement sensor to see which setting gave a reading then went from there.

The assumed working sensor was tested twice and was consistent. The suspected faulty sensor was tested in various positions etc around 8 times and all readings were low.

Im guessing the low voltage is what's causing the issue as its not high enough to register as working?
 
  Mk4 Mondeo Estate
Yeah a low voltage like that would be out of the expected operating range more than likely causing your ABS fault. 99% certain changing the sensor should cure the fault
 


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