ABS False Activation - please help

[danstine]

any advice peeps?

I have false activation of ABS when braking at slow speeds, had this for a while and now scratching head.

The sensors have been replaced twice and thrice over, they have been swapped and all working. I have replaced the wheel bearing and the CV joint, And still no luck.

I have no ABS warning light thank god but the false activation is extremely annoying as it ruins the joy of the ride. when the ABS falsely activates, i can feel vibration, juddering under my foot and hear a grinding noise from the front right wheel. as i said,swapped the sensor with the left wheel sensor and still grinding from same position :rant: :mad:

any ideas would be greatly appreciate!!! many thanks

[James.uk]

The grinding noise would indicate some other problem? Worn pads? badly fitted pads? Warped disk?
...

[danstine]

Thanks for the response, sorry i should of mentioned, if i deactivate the ABS (pulling out a sensor or fuse) the grinding goes away. It is definitely electrical....

Many Thanks!

[danstine]

Any ideas anyone? i'm going on a v-e-r-y long drive this weekend and was hoping to suss this before then.

Please note - brakes are perfectly operational and safe, however the ABS isnt to its fullest potential if needed!

[bramblp]

Any time I have experienced this in the past (three times now ) it has always been a sensor or its cable

[chrissyboy]

you really need to use a scanner to see what where the problem lays...and what the codes are saying ,as you could get the same symtoms but diffrent causes ....

[markymark]

Hi mate i have the same problem and its doing my head in too,

[neal.blackmoor]

hi there i also think i have the same problem...how do you disconect the abs and stop it working.. what fuse or relay...

[James.uk]

Taking mine in for an over active ABS tomorrow thurs PM, will report back tomorrow when I get home again.. :}
...

[danstine]

Thanks to all for your comments, it is a really annoying problem.

Ive scanned the ECU for faults myself and there were no fault codes. 1 mechanics read the same and a well known garage that take people for rides (lets call them s*hit fit for now) couldnt even access the ECU.

To disable the ABS (for test reasons) i just disconnect the lead in the engine bay, obviously cable tieing it to something solid.

James.uk let me know what you find out, that would be greatly appreciated! this grinding is killing me! thanks to all :D

glad im not the only one with this strange problem

[Platemaker]

Is it activating at low speed, such as when you slow down for a junction?

If so, it could be the pickup ring on the inside of the hub, this is NOT a toothed ring around the driveshaft as found on some vehicles. It is a smooth ring on the inside of the wheel bearing area.

They can get damaged quite easily when removing a stuck ABS sensor.

Were any of your sensors difficult to remove, drilled out?

[danstine]

The sensor was originally drilled out, i thought this but had the bearing replaced 2 days ago. problem still exists! :(

People talk of changing the reluctor ring, but there isnt one on these 75's. its just the bearing.

[danstine]

and it is activating at low speeds, coming to a stop. usually under 20mph

[James.uk]

Well we had the wheels off, fitted the spring protectors, unplugged the joints/connectors that hide in the plastic arch liner and reconnected them, checked behind both the wheels and traced both wires back to the plugs, found nothing wrong, found no fault codes either. :shrug:

Took it for a test run and everything now works as it should.. The problem is gone... :shrug:

Made the coffees for the mechanics. They said they may have caused the problem when they changed the spring and/or tyres.. So there was no charge!! :D :D :D
...

[danstine]

ah if only i was that lucky! :D glad yours is sorted!

I will take the pads apart and resit them, have a little clean up of that area and see if i have some luck!

thanks James

[markymark]

i have the same problem,and just taken the fuse out of the abs but still the same,but have notice brake pedal has a lot of play in it, wonder if that has anything to do with it,does anyone else with this brake problem have a lot of play in there brake pedal, plus does anyone have a ticking noise as well.

[crashmarks]

Is it right that you have ABS but no warning light ? I have never seen that before I cant see the logic in it how are you supposed know if you have a fault. Are you sure the ABS light just isnt working ? Perhaps somebody else could comment on that aspect !!

[danstine]

I think you have misunderstood what I meant crashmark. the problem isnt the light on the dash, if the abs goes wrong the light lights up. But my issue isnt the light, with my abs enabled I have grinding, with the abs disconnected - I dont. Therefore it must be abs related...

thats my theory. I know this is rare because ive searched high and low for an answer.

[crashmarks]

Sorry I have mis-understood re the light. I do lots of emergency brake tests in lots of different vehicles some with some without ABS and often those that have I purposly disable it. I can assure you that when ABS activates on many vehicles it is accompanied by a grinding noise. It varies from make to make but if your sure that your discs and pads are ok and when you brake firmly, but not enough to engage ABS, and you dont get any abnormal noise then everythings probably fine.

[James.uk]

My ABS light stayed off. :shrug:

My mech thought it was either muck between the sensor and the magnetic ring, of the plugs not fully connecting when they were pushed home.. :shrug:
...

[danstine]

crashmarks, my problem is normal braking under 15-20mph i get grinding and pushback from brake pedal. Im not harsh braking, its general braking ie slowing down for junction/roundabout/lights/zebra crossing etc...

Id understand if i had to slam my brakes on, or slid in ice then yes my abs would cause these symptoms but im getting it in everyday normal braking situations. which isnt normal....

If i unplug a sensor, i can approach a roundabout with perfect silence! My abs seems to be overactive... kicking in everytime i press the pedal (under 20mph)

I’ve changed the CV joint, the wheel bearing (which has the pick-ups for the sensor built in), all four sensors and my front brake pads, all to no avail.

[danstine]

My ABS light stayed off. :shrug:

My mech thought it was either muck between the sensor and the magnetic ring, of the plugs not fully connecting when they were pushed home.. :shrug:
...

Ill have the wheel off again at the weekend just to do the routine checks, i am completely at a loss. i have done the following to try and solve:


3 new sensors
clean up of general area
new wheel bearing
new cv joint
new brake pad sensor
change of brake pads
discs seem fine
As you say ":shrug:" thats me all over.... now venturing down the avenues of ABS pump??? ABS connectors in the engine bay??? rear sensors???

i just dont understand where this electrical malfunction could be coming from, its as if the ABS sensor is telling the brake to go crazy under 20mph and everything is next to brand new!! :shrug: just pure craziness! :(

[danstine]

i have the same problem,and just taken the fuse out of the abs but still the same,but have notice brake pedal has a lot of play in it, wonder if that has anything to do with it,does anyone else with this brake problem have a lot of play in there brake pedal, plus does anyone have a ticking noise as well.

Hi Mark, no i havent found a solution yet... i went to Paris and back and it still there. The ticking noise you mention i have also. kinda sounds like the tyre is hitting the abs wire but ive had a look and its tied to the body of the car - so its not that. Ive never really thought about it that much, the excessive grinding normally overules it! :getmecoat:

regards to all

[sailorhms]

I had the same problem a few weeks back....slight activation of the ABS when braking from slow speeds and the ABS warning light was not on, when the 30 amp fuse was removed, the braking was normal but the warning light(s) were on.
Replaced were; both front sensors, BOTH front wheelbearings.
Both front bearings were changed because the speedo was coming and going. The state of the magnetic rubber rings were producing the problems, they were both pitted and generally scrubbed.
can only assume that when a damaged part passed the sensor it confused it and thus produced the over zelous ABS.
So, if your problems persist I would change the other bearing even if your speedo works and if still no joy, begin the changing of the corresponding rear parts;sensors and bearing assemblies.
The ABS pump and its ECU are fairly expensive and alot more difficult to change, so eliminate the not so expensive bits first.

[COLVERT]

Post 24 above seems most sensible. :bowdown::bowdown::bowdown:
If the sensor is not getting a signal cos the ring is damaged on the bearing, then it will think the wheel has locked and so operate the anti-lock system. Hence the kick back at the pedal. :}:}:}

Colvert. ;)

[ScottRTQ]

Post 24 above seems most sensible. :bowdown::bowdown::bowdown:
If the sensor is not getting a signal cos the ring is damaged on the bearing, then it will think the wheel has locked and so operate the anti-lock system. Hence the kick back at the pedal. :}:}:}

Colvert. ;)

I must agree with this, Before my ZT I had a Nissan Primera and the ring on the CV joint had cracked which gave exactly these symptoms. Maybe something similar for you.

[GaSrAm]

It could be as simple as corrosion on the back of one of the hubs , the rear sensor only takes its reading from the back of the hub and if this is rusted it breaks the electromagnetic signal to the abs and make it think its locked however this would also show the fault light

[markymark]

Hi have you had any joy with your brakes yet mate.

[CAR-Toonist]

Interesting thread. I've had a brake noise/grinding problem ever since FNS wheel bearing replaced. Also had to have the ABS sensor done too. If I want to disable abs to check - is it ok/simpler to remove the fuse or will this cause other problems?

[sof007]

I have a squeaking noise coming from one of my front wheels, coupled with the speedo not working and the ABS light coming on (after the brakes acting over zealously for a while) and also my fuel gauge having a mind of it's own.

I thought originally that it was just the ABS sensor but I'm not beginning to think that it may be the front wheel bearing.

Where's the best place to get one of these?

[sailorhms]

I just got my two front bearings from Ebay, around 40 quid each, but i'll bet they would be double that to buy from a motor factors and so far they have performed as they should..changing them got my ABS warning light off anyways.

[sof007]

hmmm, I must have a look. I don't suppose you know what seller you got these from?

[James.uk]

My local garage supplied me with front wheel bearings at £35 each..

But -- the abs sensors were about £75 each!!! :mad: again, from my local garage.. :}
...

[sailorhms]

hmmm, I must have a look. I don't suppose you know what seller you got these from?

Its just a matter of searching Rover 75 wheelbearing, there are'nt that many different sellers selling them.
The sensors fro around 20 quid seem to do their job competently as well.

[danstine]

SOF007 your symptoms are definitly ABS sensor related. crazy acting fuel guage, speedo not working and abs light is your front offside (drivers) sensor....change that and your sorted.

speedo works off that one.

no luck with false activation yet, saving to change front nearside cv joint and bearing. cost me a fortune to get this far! I WILL FIND YOU!

Regards

[petersmith666]

hi i had the same problem turned out to be a cracked abs ring hope it helps

[James.uk]

I think cracked abs rings are the mechanical ones as on Mazdas etc, our cars work off elec impulses from the magnetic part of the wheel bearing.. :)

In my case the problem has slowly vanished, my mech checked the car out, found nothing wrong, and said to give it time and it could sort itself out, and over 1000 miles ish it has gone back to normal.. :shrug: :D
...

[herman0786]

any advice peeps?

I have false activation of ABS when braking at slow speeds, had this for a while and now scratching head.

The sensors have been replaced twice and thrice over, they have been swapped and all working. I have replaced the wheel bearing and the CV joint, And still no luck.

I have no ABS warning light thank god but the false activation is extremely annoying as it ruins the joy of the ride. when the ABS falsely activates, i can feel vibration, juddering under my foot and hear a grinding noise from the front right wheel. as i said,swapped the sensor with the left wheel sensor and still grinding from same position :rant: :mad:

any ideas would be greatly appreciate!!! many thanks


I had the same problems as ur having danstine,just after i had new tyres fitted. I asked a few mechanics wat the prob could be and all said it was nothing to do with the tyres.

Was then told by a mech that my ABS pump was gone, oh i forgot to mention when breaking i got that grinding u talked about and also if i had to brake hard coming up to a junction the peddle would shoot down half an inch (very scary at the beginning,but got used to it)

abs light only came on after driving steadily at around 60 mph, but anyway to cut a long story short got new tyres fitted for mot and car is perfect ever since

so maybe thats another option, i know its bizarre but it worked for me

[shaun_kaz]

Hi this site is greats loads of information. I too have a Rover 75 with the dreaded ABS fault which grinds at low speeds when braking gently. I pulled the fuse out which has stopped this but now the ABS and handbrake light are on all the time and my MOT is due in May so it needs to be done.. Last weekend I took ff all the wheels and checked the brake pads all where ok. I did find though that drivers side front wheel has excessive play due to the ball joints in the lower arm and on the passenger side the track rod end ball joint has excessive play. So i have bought x2 lower arms and x2 track rod ends which I fit this weekend along with new antiroll bar struts. It might be worth taking the hubs off whilst strpped down and checking the bearings and inner ring. I'll let you know how I get on..

[Anthony & Maricel]

:D ABS sensors are £17 ea on ebay :D

[rossocorsa]

I think the reason for a false low speed ABS activation is very very small differences in the signal between the two sensors this makes the abs ECU 'think' that there is a lock up situation and activates, I had this after a sensor change i think it's due to fractionally incorrect seating of a sensor or dirt on the bearing,also I've seen the theory on the 'net somewhere that slight surface corrosion under the sensor can be enough to very slightly lift it causing marginally differing signals

[Anthony & Maricel]

Mine was due to the wear of the sensor cable on the inside hub which eventually wore through the cable, this caused the same symptoms ABS activating at slow speed and eventually the abs light came on.

Something to look for when ABS problems start to occur.

[James.uk]

The two front abs sensors I bought were £75 each! :shrug:

And yes a tiny bit of foreign matter under the ABS sensor can cause the ABS to come on at times..

I am having the same problem, but it is getting better all the time.. :shrug:
...

[Anthony & Maricel]

They are £17 ea on ebay, so check ebay before allowing a greasy monkey to charge you lots of wonga + labour

[BigRuss]

I think the reason for a false low speed ABS activation is very very small differences in the signal between the two sensors this makes the abs ECU 'think' that there is a lock up situation and activates, I had this after a sensor change i think it's due to fractionally incorrect seating of a sensor or dirt on the bearing,also I've seen the theory on the 'net somewhere that slight surface corrosion under the sensor can be enough to very slightly lift it causing marginally differing signals


A distinct possibility, these are what are known as plausibility faults on the abs system when you diagnose it on T4.

the cause is as you say dirt, corrosion, damaged bearing surface or a badly seated sensor.

The variance in signal isn't enough to illuminate the warning lamp but may be enough to cause the problem as described.

Sometimes it will clear on it's own if it's down to dirt, but corrosion or a badly seated sensor would require the removal and replacement of the sensor to fix it.

Just a point here, there seems reading this thread to be an assumption that it's down to one of the front sensors causing the problem, it may well be one of the rear ones ;)

Russ