ABS SENSOR PROBLEM

[Hayley Dawes]

Can anyone help??? I own an L reg clio 2.0 litre 16v Everytime i put my foot on the break it makes a juddering noise and feel through the pedal, whether i break hard or soft. I have had it put on a machine to test it, but it states no fault found, so the abs is obviously working, but too much. The machine that was used to test it, was grounded, so therefore the car was nt tested whilst moving. I have booked it in with another garage that will be able to test the sensors individually whilst moving.

Has anyone any suggestions to anything else i could possibly try??? Would be extremely grateful

 

[Mike@Rentech]

Hi sounds like one of your ABS sensor pickups is bent.
(caused by stone getting between pickup and sensor)

Had this a few times on some Renaults, have a look at the sensor and pickup ring make sure they all look to be good.

If one is damaged it will stick out like a sore thumb.

 

[tonykart]

try to drive VERY slow just moving see if the judddering is still there. ABS kicks in above 15 Mph under this speed is doesnt work. So at this point you know if it is the ABS or your brakes themself (e.g. bend disks due to overheating)



Good Luck,



cheers

 

[JAY172]

tell the garage to observe the wheel sensor speed outputs when moving they will probably find one of the sensor reading is out compared to the others.look at the sensor for damage and check the target teeth on the driveshaft/rear discs as well(eg tooth missing).abs is active above about 6mph

 

[Hayley Dawes]

Thanks a lot for all your suggestions

It must be the sensors as the light keeps coming on every so often. It does also do it at a very low speed . We have checked the teeth where the sensor picks up and they seem to be fine, we have cleaned them to get all the sh*t out aswell.

Also the other day i turned the car on and the abs light stayed on for a good few miles, until i turned the engine off when i stopped. Whilst the light was on, the juddering stopped altogether, so does this mean that the compuer has stored the problem when the light was on so therefore stopped the juddering from happening?

 

[JAY172]

you can do a resistance check on the sensors.ill find out the values so you can check them.while ever your warning light is on the abs fuction is turned off so you only have the normal braking system.

 

[KDF]

Thats a good point about the 6mph thing, noticed that in the snow.. the abs would kick in if you were doing about 10mph but not slower than that (hard to tell exactly cause speedo doesnt really read that low) and the wheels would lock.

 

[JAY172]

the computer self tests the sensors(circuit continuity and speed output) at 6 mph then activates abs if no faults are detected.

 

[Hayley Dawes]

Cheers everyone.

JAY 172, how do you do a resistance check on the sensors, if you dont mind explaining to me? I have had the car checked in a garage on the abs machine, but this was before the light came on, and the car was also standing still whilst they checked it. The machine came up with no fault found. I have it booked in another garage that can test it whilst it is moving, its a kind of snap on machine. Hopefully they will be able to pick up the fault, what dya reckon????

 

[JAY172]

unplug the sensor and put a multimeter across the pins.put the multimeter to ohms and see what you get.ill have to find out the value for you but i think its 1.6ohms. ill check what it is.

 

[Hayley Dawes]

JAY172

Do you mean to test the abs unit itself or the sensor, i am presuming you mean the sensor, but just checking with you.

Thank you so much for your help.

 

[KDF]

He means the sensor.. a reading of near/zero may indicate a short, if it say OC on the multimeter it means open circut.

 

[Hayley Dawes]

Ok cheers KDF, ill do that over the weekend and let you know the outcome.

 

[JAY172]

check all 4 wheel sensors mate.