The M3 motorway triggers my ABS warning light
Discussion
Here's an odd one: Driving down the M3 southbound; for the last 4 times in succession the ABS warning light has come on at the same place - near the blue km/milepost that says "M3 A 89.4" (near Micheldever, between Basingstoke and Winchester).
What on earth is going on?
It's not just length of journey, because I have made those 4 journeys with different start points.
Doesn't happen northbound, nor indeed anywhere else in the country yet.
I'm starting to suspect there's some secret government place near there that's emitting radiation!
What on earth is going on?
It's not just length of journey, because I have made those 4 journeys with different start points.
Doesn't happen northbound, nor indeed anywhere else in the country yet.
I'm starting to suspect there's some secret government place near there that's emitting radiation!
Krikkit said:
Bad road surface upsetting a dodgy sensor?
Nothing obvious there. In fact there is a worse bump in the surface northbound near the same location, where they've put up a bump sign, and this doesn't trigger it.https://www.google.co.uk/maps/@51.147938,-1.241940...
On my old Honda the brake warning light always used to come on just as I braked to slow at the top of the sliproad as I came off the last A road on the way home from work. After a few weeks of this the brake switch failed. Apart from not being able to get the car out of 'P' when starting it, that brake warning light in that particular place was the only symptom.
M4cruiser said:
the ABS warning light has come on at the same place - near the blue km/milepost that says "M3 A 89.4" (near Micheldever, between Basingstoke and Winchester).
^ and I should have added that the next time I switch off and reset, it's all back to normal, so it's just a one-off triggering.Its Just Adz said:
What car? Does it have front facing sensors?
My truck has AEBS and can pick up the shadow from a bridge and trigger emergency braking.
No front sensors nor AEB, just the abs sensors on the abs ring, presumably they are so closely coupled that nothing else should be able to interfere.My truck has AEBS and can pick up the shadow from a bridge and trigger emergency braking.
It does happen near a bridge, but then there are many other bridges (in fact all of them) that don't cause any issues at all.
Had similar issues with my e90 330i.
ABS warning light would always go on near the M1/A38 junction, going southbound on A38.
I could do 100 miles on a motorway and as soon as I had reached particular part of that road it would trigger.
In the end I replaced rear sensor and bearing.
Stoped after that.
ABS warning light would always go on near the M1/A38 junction, going southbound on A38.
I could do 100 miles on a motorway and as soon as I had reached particular part of that road it would trigger.
In the end I replaced rear sensor and bearing.
Stoped after that.
996TT02 said:
Maybe due to trailing throttle or brake feathering or even application of throttle in combo with weird road surface perhaps dislevel in the slabs causes a single wheel to become momentarily and imperceptibly airborne but thus changes rotational speed, so abs detects this.
Was going to say the same thing, maybe there is something with the road surface that only affects the grip on one side if the car, just enough to trigger the abs sensor.Have you tried in different lanes on the same piece of road?
Maybe lift off slightly at the place it happens so there isn't a lot of torque being applied?
A dodgy bit of road and an abs ring that is about to give up?
Fiedka said:
Had similar issues with my e90 330i.
ABS warning light would always go on near the M1/A38 junction, going southbound on A38.
I could do 100 miles on a motorway and as soon as I had reached particular part of that road it would trigger.
In the end I replaced rear sensor and bearing.
Stoped after that.
Update, I eventually found that the ABS fault could be caused (sometimes) by going over 60mph, below that it didn't happen - which explains why it rarely happened on my normal journeys.ABS warning light would always go on near the M1/A38 junction, going southbound on A38.
I could do 100 miles on a motorway and as soon as I had reached particular part of that road it would trigger.
In the end I replaced rear sensor and bearing.
Stoped after that.
I traced the fault by driving with the scanner plugged in, until the light came on again, parked up and read the codes without switching off. Code 21 - Right front sensor.
So this week, replaced the sensor, cleared the codes. Now there are no codes, abs light is off, yet the ABS is triggering on that wheel at very low speeds (i.e. 5mph, manoeuvring in a car park) but not at higher speeds in normal driving. I can feel it in the pedal, and hear the loud clicking.
What could be going on now!?
GeniusOfLove said:
The reluctor rings can get corrosion on them, or on some cars underneath them that distorts their shape.
I had a look at it through the hole once I'd got the old sensor out, and it did look a bit brown. It looks like it's integral with the drive shaft, so maybe a whole new one will fix it? Will cost more than the sensor though!I had a car that triggered an ABS fault on rough roads or pot holes due to a faulty rear damper.
The damper was completely shot, so the uncontrolled reverberation from high frequency impacts was causing wheel speed oscillations that were deemed as "out of parameter threshold" and therefore triggering a ABS/TC fault.
It wouldn't explain why it happens at parking speeds though, most ABS sensors wouldn't register a wheel-speed related fault at <5mph, only if the sensor itself was damaged or unplugged.
The damper was completely shot, so the uncontrolled reverberation from high frequency impacts was causing wheel speed oscillations that were deemed as "out of parameter threshold" and therefore triggering a ABS/TC fault.
It wouldn't explain why it happens at parking speeds though, most ABS sensors wouldn't register a wheel-speed related fault at <5mph, only if the sensor itself was damaged or unplugged.
M4cruiser said:
GeniusOfLove said:
The reluctor rings can get corrosion on them, or on some cars underneath them that distorts their shape.
I had a look at it through the hole once I'd got the old sensor out, and it did look a bit brown. It looks like it's integral with the drive shaft, so maybe a whole new one will fix it? Will cost more than the sensor though!They go slightly out of shape from the corrosion underneath so the speed signal from one wheel is fluctuating constantly. I noticed it on an XJ8 from a very slight sensation of speed variation on cruise control, fixing it also fixed poor gear shifting because the TCM was getting wonky speed signals.
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