As per the title.
On the way home yetserday thought I'd see what the freebie special would do, but why would the ABS light come on at speed? Normally they don't work cos of crappy rotor slots or dud connections, but at higher speeds the signal should be stronger, not weaker so why drop out? woorks noramlly after stopping and restarting.
Not really that important and it'll probally never go there again but it would be nice to know!
One thing I did notice is just how loud they are if the screen seal is missing!! anything above 60 really whistles
ABS warning on at 110
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tecw1979
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docchevron1472
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Mine has a totally random habit of throwing the ABS light on but I think it's a duff cable on the O/S/F sensor. Doesn't scare me into slowing down though, I just boot the thing harder to show it who's bosstecw1979 wrote:its the bx's way of saying... " i really dont want to go this fast, lets scare u into slowing down!"
iffy sender cables are erratic like that, or maybe theres vibration neer the abs pump/ecu at speed?
Cheers
Chris G
1990 BX 16v Phase 2
1989 BX TD hybrid
1971 BL 350FG Ambulance (unique)
1993 Dennis Lance 132
That's when I reach for my Revolver
1989 BX TD hybrid
1971 BL 350FG Ambulance (unique)
1993 Dennis Lance 132
That's when I reach for my Revolver
ABS
Guess which warning lamp my BX is sporting today 
Another sensor to change I suspect but the car will be laid up again at the end of th emonth so no hurry and i have a box full of spares
Cheers
Luke
Another sensor to change I suspect but the car will be laid up again at the end of th emonth so no hurry and i have a box full of spares
Cheers
Luke
Please call me Luke 
1989 BX 16valve White 70k almost up to scratch
1989 BX 16valve White 70k almost up to scratch
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Anonymous
I've got the opposite problem, the ABS quite often kicks in at about 5mph 
really handy, 'specialy when negotiating the traffic light forrest that my home town has recently become 
perhaps that's why the front bumper had so much minor damage, anyway it's off for its MOT tomorrow so fingers crossed, 'though it wasn't a problem last year.
Martyn
really handy, 'specialy when negotiating the traffic light forrest that my home town has recently become perhaps that's why the front bumper had so much minor damage, anyway it's off for its MOT tomorrow so fingers crossed, 'though it wasn't a problem last year.Martyn
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tecw1979
I know this might sound a bit fanciful, but how's this for a theory?
In layman's terms (because I don't know the technical ones)
the ABS works on the magnetised sensor counting the teeth on the serrated wheels.
If one wheels count varies from the others, then the system releases the pressure to that particular wheel.
If any fault/abnormality arises, then the warning light comes on.
By the same token, as with sensors associated with engine management, most ECUs are controlled by sensors which have parameters or "ranges" that they work within, so if for any reason one of these registers a reading beyond the scope of its range, it will show a malfunction.
The theory is this:
The ABS counts the teeth per wheel via the sensors, so if either through age or corrosion, either the magnet in the sensor gets weak or the teeth on the serrated wheel start to diminish in the gap, could this then give the control unit false information that it can't process?
By that I mean normally (or at lower speeds in the case of a faulty unit) it sees the sensing teeth like this:- !...!...!...!...! but due to the above factors, at above 110 they suddenly seem like this:- !.!.!.!.!.! and thjis takes it out of it's range to read?
From past experience I've found usually that a faulty sensor (as in one with an internal break) will not "reset" the fault light once it has registered, whereas one operating outside its designed range I think possibly might.
Any thoughts?
Alan S
In layman's terms (because I don't know the technical ones)
the ABS works on the magnetised sensor counting the teeth on the serrated wheels.If one wheels count varies from the others, then the system releases the pressure to that particular wheel.
If any fault/abnormality arises, then the warning light comes on.
By the same token, as with sensors associated with engine management, most ECUs are controlled by sensors which have parameters or "ranges" that they work within, so if for any reason one of these registers a reading beyond the scope of its range, it will show a malfunction.
The theory is this:
The ABS counts the teeth per wheel via the sensors, so if either through age or corrosion, either the magnet in the sensor gets weak or the teeth on the serrated wheel start to diminish in the gap, could this then give the control unit false information that it can't process?
By that I mean normally (or at lower speeds in the case of a faulty unit) it sees the sensing teeth like this:- !...!...!...!...! but due to the above factors, at above 110 they suddenly seem like this:- !.!.!.!.!.! and thjis takes it out of it's range to read?
From past experience I've found usually that a faulty sensor (as in one with an internal break) will not "reset" the fault light once it has registered, whereas one operating outside its designed range I think possibly might.
Any thoughts?
Alan S
As I understand it the sensors on a BX and most others don't have magnets, they are a coil which is energised, at a lowish level, in an unregulated circuit, therby creating a field around whatever is in front (and behind) if whatever is stationary it has no effect, and if its moving its changing response alters the current that the coil draws, therby altering its voltage, therby giving a signal, in this case a stepped one as the wheel is stepped. The characteristics of the moving lump in front are known as their reluctance, all very exciting!
The ratio between peaks and troughs is fixed only the ferquency changes, this is usually processed as a digital signal as Alan says, either leading edge triggered or trailing edge trigered, the system is rarely bothered about the detail in the middle!
In this case the gaops may contain rust which whilst not ideal does have a reluctance value opf its own, and this is higher than air, so maybe at higher speed when the signals are stronger, this is sufficient to fudge the signal, (like the missing teeth used in TDC systems)
Back to the practical question in hand, does the ECU reset as suggested above when a parameter fault occurs, in which case the Crap can't be my issue, or do all faults kick the system off untill reset?
In my case I probally just need to clean all the rust off and see if it makes any difference!!!
The ratio between peaks and troughs is fixed only the ferquency changes, this is usually processed as a digital signal as Alan says, either leading edge triggered or trailing edge trigered, the system is rarely bothered about the detail in the middle!
In this case the gaops may contain rust which whilst not ideal does have a reluctance value opf its own, and this is higher than air, so maybe at higher speed when the signals are stronger, this is sufficient to fudge the signal, (like the missing teeth used in TDC systems)
Back to the practical question in hand, does the ECU reset as suggested above when a parameter fault occurs, in which case the Crap can't be my issue, or do all faults kick the system off untill reset?
In my case I probally just need to clean all the rust off and see if it makes any difference!!!
ollie,
I've never gone into too much detail with the magnetics or whatever with the sensors, but I didn't think there was any actual current heading down there, if there is, we're back to electro magnetics then I presume...same girl different skirt.
As regards the re-setting of the ABS ECU, I've only ever had a couple of instances of problems and both involved n/s front sensor when the holding bracket on the strut broke and allowed the outer sheath of the coax to fracture. In each case when we were troubleshooting, I held the sensor lead taut using tape and heatshrink which would start up and show the warning light, but if the car was switched off and the cable held so as to prevent the circuit from breaking and then re-started, it would act as normal by switching off the light as soon as the problem was rectified and without having to disconnect the battery as is done with the engine ECU.
I think the earthing on these also can raise some weird faults at times. Currently I find mine doesn't switch the light off until I hit the brake pedal. As my driveway is over 100 metres, I've been able to test if the ABS actually works in that situation and have discovered that if I drive down my driveway with the light on and hit the brakes hard, the light goes off and the ABS activates, so I take it from that it could be a dodgy earth that seems to come right when the brakes are applied hard. If I don't brake hard, the light stays on until I do.
If we didn't have BXs what would we do to keep our minds active...go dancing?
Alan S
I've never gone into too much detail with the magnetics or whatever with the sensors, but I didn't think there was any actual current heading down there, if there is, we're back to electro magnetics then I presume...same girl different skirt.
As regards the re-setting of the ABS ECU, I've only ever had a couple of instances of problems and both involved n/s front sensor when the holding bracket on the strut broke and allowed the outer sheath of the coax to fracture. In each case when we were troubleshooting, I held the sensor lead taut using tape and heatshrink which would start up and show the warning light, but if the car was switched off and the cable held so as to prevent the circuit from breaking and then re-started, it would act as normal by switching off the light as soon as the problem was rectified and without having to disconnect the battery as is done with the engine ECU.
I think the earthing on these also can raise some weird faults at times. Currently I find mine doesn't switch the light off until I hit the brake pedal. As my driveway is over 100 metres, I've been able to test if the ABS actually works in that situation and have discovered that if I drive down my driveway with the light on and hit the brakes hard, the light goes off and the ABS activates, so I take it from that it could be a dodgy earth that seems to come right when the brakes are applied hard. If I don't brake hard, the light stays on until I do.
If we didn't have BXs what would we do to keep our minds active...go dancing?
Alan S