Weird abs fault
Discussion
I am trying to fix my daughter's 2009 meriva but am starting to run out of ideas...
The problem is a graunching noise, once per wheel revolution. Only under light braking. Front offside. Sounds just like a big lump of rust on the disc catching on the brake pads. Except it isn't as the discs and pads have been changed.
Also, after a lot of messing, I found that if I disconnect the abs sensor for that wheel the noise stops. Just unplugging it fixes it, I can leave the sensor in place so it is not the sensor catching on the ring.
So, my assumption was it must be abs related and was probably a faulty sensor. So I changed the sensor and it still does it.
Perhaps connected, when I changed the discs I found the Abs ring on the hub was cracked and a cv boot was dodgy, so the whole driveshaft was replaced. The noise was present before these changes.
I am now at a loss, any ideas what could be causing it?
The problem is a graunching noise, once per wheel revolution. Only under light braking. Front offside. Sounds just like a big lump of rust on the disc catching on the brake pads. Except it isn't as the discs and pads have been changed.
Also, after a lot of messing, I found that if I disconnect the abs sensor for that wheel the noise stops. Just unplugging it fixes it, I can leave the sensor in place so it is not the sensor catching on the ring.
So, my assumption was it must be abs related and was probably a faulty sensor. So I changed the sensor and it still does it.
Perhaps connected, when I changed the discs I found the Abs ring on the hub was cracked and a cv boot was dodgy, so the whole driveshaft was replaced. The noise was present before these changes.
I am now at a loss, any ideas what could be causing it?
A good point. I assumed that it would not be that as it would then show the abs light on the dash (which does happen when I unplug it). I guess that is not guaranteed though.
I was driving it today and talking to my daughter and had another thought. Before she got it it had the front brake pipes and hoses replaced, not very well. The pedal does have quite a long travel although it does firm up ok. I was wondering if some air might be confusing the abs although I am not sure if that is even possible.
I was driving it today and talking to my daughter and had another thought. Before she got it it had the front brake pipes and hoses replaced, not very well. The pedal does have quite a long travel although it does firm up ok. I was wondering if some air might be confusing the abs although I am not sure if that is even possible.
Is it definitely once per wheel revolution?
That's usually just a dent in the back of the plate that protects the back of the disc from stones.
Might help to diagnose if you leave all sensors connected but remove the fuse for the ABS then see if it still happens, testing it in a safe non-road environment obviously.
Could it be coming from the ABS pump?
Does it feel like it's actually pulsing the brakes at all?
Have you tried braking much much harder, as to actually trigger the ABS?
That's usually just a dent in the back of the plate that protects the back of the disc from stones.
Might help to diagnose if you leave all sensors connected but remove the fuse for the ABS then see if it still happens, testing it in a safe non-road environment obviously.
Could it be coming from the ABS pump?
Does it feel like it's actually pulsing the brakes at all?
Have you tried braking much much harder, as to actually trigger the ABS?
The cable connections are worth checking if it has under wheel arch connectors, they get a hard life.
Try some wd40 in them and put together/take apart a few times.
I’d usually take a look at live data on a diagnostic tool when a fault like this happens, you can usually see a loss of wheel speed feedback on there when it happens.
Try some wd40 in them and put together/take apart a few times.
I’d usually take a look at live data on a diagnostic tool when a fault like this happens, you can usually see a loss of wheel speed feedback on there when it happens.
scarble said:
Is it definitely once per wheel revolution?
That's usually just a dent in the back of the plate that protects the back of the disc from stones.
Might help to diagnose if you leave all sensors connected but remove the fuse for the ABS then see if it still happens, testing it in a safe non-road environment obviously.
Could it be coming from the ABS pump?
Does it feel like it's actually pulsing the brakes at all?
Have you tried braking much much harder, as to actually trigger the ABS?
It is roughly one per rev. I could not be sure it is exactly one per rev though. I have ruled out mechanical issues like the backplate as it definitely stops happening when that sensor is unplugged. Hence my assumption it must be abs related. I will try the abs fuse.That's usually just a dent in the back of the plate that protects the back of the disc from stones.
Might help to diagnose if you leave all sensors connected but remove the fuse for the ABS then see if it still happens, testing it in a safe non-road environment obviously.
Could it be coming from the ABS pump?
Does it feel like it's actually pulsing the brakes at all?
Have you tried braking much much harder, as to actually trigger the ABS?
You can feel it through the pedal but it is just a single pulse, not the rapid pulsing of normal abs.
This only happens on gentle braking. Firm braking and it does not happen. Hard enough to operate the abs and the abs feels normal.
Belle427 said:
The cable connections are worth checking if it has under wheel arch connectors, they get a hard life.
Try some wd40 in them and put together/take apart a few times.
I’d usually take a look at live data on a diagnostic tool when a fault like this happens, you can usually see a loss of wheel speed feedback on there when it happens.
The connections look ok but I will definitely give them a good clean up.Try some wd40 in them and put together/take apart a few times.
I’d usually take a look at live data on a diagnostic tool when a fault like this happens, you can usually see a loss of wheel speed feedback on there when it happens.
Unfortunately my obd reader is 200 miles away but you are right, it would be sensible to look at live data. I think I might have to take the car home with me for a proper look.
😞
Matt_E_Mulsion said:
I'll have a guess that the abs ring on that hub is broken/knackered/bent and the sensor can't detect part of it, hence once per revolution it's trying to operate the abs system.
I would agree, except the ring has already been replaced, along with the whole driveshaft. I have checked it hasn't failed again but maybe I need to check again.Thinking about it, the previous symptoms where the abs light coming on at speed.
First things first
If you disconnect any one of the four ABS sensors the system will no longer be active and the ABS warning light will be illuminated
The above is something to consider when disconnecting the one sensor at the wheel that's giving trouble, you could disconnect any one sensor and get the same result (ABS light on, ABS not active and brake problem gone)
Have you checked that the new drive-shaft has the same number teeth for ABS sensing as the old drive-shaft has?
Should all parts be correct, there is surely a sensor not reading the wheel speed correctly and that can only be caused by a failing sensor, incorrect sensor to ring air gap, dirt on sensor/ring, incorrect sensor to ring alignment or worst case scenario and very doubtful, a faulty ABS ECU
If you disconnect any one of the four ABS sensors the system will no longer be active and the ABS warning light will be illuminated
The above is something to consider when disconnecting the one sensor at the wheel that's giving trouble, you could disconnect any one sensor and get the same result (ABS light on, ABS not active and brake problem gone)
Have you checked that the new drive-shaft has the same number teeth for ABS sensing as the old drive-shaft has?
Should all parts be correct, there is surely a sensor not reading the wheel speed correctly and that can only be caused by a failing sensor, incorrect sensor to ring air gap, dirt on sensor/ring, incorrect sensor to ring alignment or worst case scenario and very doubtful, a faulty ABS ECU
Penelope Stopit said:
First things first
If you disconnect any one of the four ABS sensors the system will no longer be active and the ABS warning light will be illuminated
The above is something to consider when disconnecting the one sensor at the wheel that's giving trouble, you could disconnect any one sensor and get the same result (ABS light on, ABS not active and brake problem gone)
Have you checked that the new drive-shaft has the same number teeth for ABS sensing as the old drive-shaft has?
Should all parts be correct, there is surely a sensor not reading the wheel speed correctly and that can only be caused by a failing sensor, incorrect sensor to ring air gap, dirt on sensor/ring, incorrect sensor to ring alignment or worst case scenario and very doubtful, a faulty ABS ECU
This is going to be a bit vague as I am trying to fix the thing in the rain on a side street in Plymouth with all my tools 200 miles away. I am also relying on my dodgy memory of my previous attempt 4 months ago.If you disconnect any one of the four ABS sensors the system will no longer be active and the ABS warning light will be illuminated
The above is something to consider when disconnecting the one sensor at the wheel that's giving trouble, you could disconnect any one sensor and get the same result (ABS light on, ABS not active and brake problem gone)
Have you checked that the new drive-shaft has the same number teeth for ABS sensing as the old drive-shaft has?
Should all parts be correct, there is surely a sensor not reading the wheel speed correctly and that can only be caused by a failing sensor, incorrect sensor to ring air gap, dirt on sensor/ring, incorrect sensor to ring alignment or worst case scenario and very doubtful, a faulty ABS ECU
Anyway, enough excuses......
I am pretty sure I already tried disconnecting one of the other sensors and the fault persisted. Although that might have been when it did have a broken abs ring. I need to recheck...
I did not check the number of teeth on the ring although it definitely looked the same. Again something to recheck.
What you say does make a lot of sense though, I think disconnecting the sensor proves it is abs related. You are right, I need to go back to basics but I am not keen to do that here.
Part of the problem is my daughter already took it to a garage who supposedly checked everything but could find anything wrong despite being able to reproduce the fault.
gnc said:
have you had a diagnostic on it ? if the peddle is lumpy, could be abs kicking in, had similar on my volvo. could be the ring or the sensor, had a broken ring on the volvo
geof
No, no diagnostics yet, by me at least. I am not sure if the garage my daughter took it to did any.geof
I think I have a vauxhall reader at home, but not here.
I am currently waiting for the car to be MOTed, will be interesting to see whether they pass it
brman said:
Penelope Stopit said:
First things first
If you disconnect any one of the four ABS sensors the system will no longer be active and the ABS warning light will be illuminated
The above is something to consider when disconnecting the one sensor at the wheel that's giving trouble, you could disconnect any one sensor and get the same result (ABS light on, ABS not active and brake problem gone)
Have you checked that the new drive-shaft has the same number teeth for ABS sensing as the old drive-shaft has?
Should all parts be correct, there is surely a sensor not reading the wheel speed correctly and that can only be caused by a failing sensor, incorrect sensor to ring air gap, dirt on sensor/ring, incorrect sensor to ring alignment or worst case scenario and very doubtful, a faulty ABS ECU
This is going to be a bit vague as I am trying to fix the thing in the rain on a side street in Plymouth with all my tools 200 miles away. I am also relying on my dodgy memory of my previous attempt 4 months ago.If you disconnect any one of the four ABS sensors the system will no longer be active and the ABS warning light will be illuminated
The above is something to consider when disconnecting the one sensor at the wheel that's giving trouble, you could disconnect any one sensor and get the same result (ABS light on, ABS not active and brake problem gone)
Have you checked that the new drive-shaft has the same number teeth for ABS sensing as the old drive-shaft has?
Should all parts be correct, there is surely a sensor not reading the wheel speed correctly and that can only be caused by a failing sensor, incorrect sensor to ring air gap, dirt on sensor/ring, incorrect sensor to ring alignment or worst case scenario and very doubtful, a faulty ABS ECU
Anyway, enough excuses......
I am pretty sure I already tried disconnecting one of the other sensors and the fault persisted. Although that might have been when it did have a broken abs ring. I need to recheck...
I did not check the number of teeth on the ring although it definitely looked the same. Again something to recheck.
What you say does make a lot of sense though, I think disconnecting the sensor proves it is abs related. You are right, I need to go back to basics but I am not keen to do that here.
Part of the problem is my daughter already took it to a garage who supposedly checked everything but could find anything wrong despite being able to reproduce the fault.
perhaps you would be better leaving the ABS off until the weather or car location improves
Matt_E_Mulsion said:
Has the new ring got bent during the fitting of the new components?
Possibly, although I would be surprised as I fitted it and I am not normally that ham fisted. Definitely worth checking though.On the plus side the car passed its MOT today although there were advisories for subframe rust. I've never really been a fan of Vauxhall's and this car is not improving that view!
I have also pulled the fuse on the abs and the problem stopped, so definitely related to the abs in someway. But I knew that anyway.
Looks like I will be driving it back to my house so I can investigate further. A pain but better than any more attempts on the side of the road here....
a small update:
I managed to get op-com running, cleared the faults (there were historic ones as I had been disconnecting the sensors), went for a drive and reproduced the fault. On re-reading the fault codes - there were none.....
Not only that, but live data from the abs showed that it was not firing and wheel sensor results looked ok.
Not sure where that leaves me.......
(edit to clarify live data)
I managed to get op-com running, cleared the faults (there were historic ones as I had been disconnecting the sensors), went for a drive and reproduced the fault. On re-reading the fault codes - there were none.....
Not only that, but live data from the abs showed that it was not firing and wheel sensor results looked ok.
Not sure where that leaves me.......
(edit to clarify live data)
Edited by brman on Tuesday 10th March 17:59
another update just in case anyone cares:
I was driving the car last week and the abs light came on when driving at speed. Great, might have a chance of a fault code. Sure enough, nearside front sensor bad reading.
I have checked out that side and the abs ring is split, ie the same as what I found on the other side about a year. So it looks like I was chasing a red herring. I had thought it was the right hand side because a) it sounded like it was and b) that is where I had problems before.
Turns out it was the same fault the other side
So, given a complete driveshaft with abs ring is £28 I am not going to mess around trying to change just the ring. New driveshaft on order!
I was driving the car last week and the abs light came on when driving at speed. Great, might have a chance of a fault code. Sure enough, nearside front sensor bad reading.
I have checked out that side and the abs ring is split, ie the same as what I found on the other side about a year. So it looks like I was chasing a red herring. I had thought it was the right hand side because a) it sounded like it was and b) that is where I had problems before.
Turns out it was the same fault the other side
So, given a complete driveshaft with abs ring is £28 I am not going to mess around trying to change just the ring. New driveshaft on order!
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