ABS comes on when I hit a pothole

merlinpjl · Jul 23, 2012

As I drive along and begin to slow for a junction etc... if a hit a pothole or bump in the road, the ABS cuts in.

It even did it the other day when I was turning the car around at very low speed and had to mount a curb, as the car came down off the curb at almost full lock and with pedal pressure on the brake, the ABS cut in.

This is an automatic P38 petrol.

Any ideas?

wammers · Jul 23, 2012

Possibly an ECU problem don't think ABS should come in at all below 10 mph. When wheels are turning on lock one turns considerably faster than the other. The ABS ECU should allow for this. Stick it on diagnostics and see what comes up.

eightinavee · Jul 23, 2012

A low reading from one of the wheel speed sensors will cause this,make sure they are all fully seated and check the wheel bearings for play before paying for a diganostic session.Pre 99 my abs ecu's almost never go wrong,99-02 ecu's usually just fail with a fault that wont clear which is one sensor shorted to another,or it thinks that the sensors are connected to the wrong wheels.

merlinpjl · Jul 27, 2012

I take it the wheel sensors can move then, I haven't looked closely enough before. Away on holiday at the moment so can't jack the car up just yet.

Saint.V8 · Jul 27, 2012

Yep they *can* move in the P38, they are just push fitted.

MrGorsky · Jul 27, 2012

Mine does this too. There's a roundabout at the bottom of a hill I drive across a lot with pot holes on the approach.

I'm always breaking as I approach the roundabout and the abs always kicks in as I hit the pot holes. I'd be doing more than 10 mph I expect.

To be honest I just put it down to some "rough road, hill decent, off roading" thing and thought it was normal. I don't remember seeing any abs light com eon the dash as it's doing it. Does a light come on when abs is active?

I'll check my abs sensors are seated though. Is there a correct adjustment to go for or do they just push all the way in?

Saint.V8 · Jul 27, 2012

MrGorsky said:
Mine does this too. There's a roundabout at the bottom of a hill I drive across a lot with pot holes on the approach.

I'm always breaking as I approach the roundabout and the abs always kicks in as I hit the pot holes. I'd be doing more than 10 mph I expect.

To be honest I just put it down to some "rough road, hill decent, off roading" thing and thought it was normal. I don't remember seeing any abs light com eon the dash as it's doing it. Does a light come on when abs is active?

I'll check my abs sensors are seated though. Is there a correct adjustment to go for or do they just push all the way in?

Push all the way in they will self gap...

merlinpjl · Jul 27, 2012

No ABS light on dash when it does it, just the vibration of the ABS doing it's thing.

What do the sensor look like?

I know it's not a big area around the wheel hubs but prefer to know what I am looking for?

Saint.V8 · Jul 27, 2012

As attached from RAVE....

The P38 system is very sensative, so may not be a fault

merlinpjl · Jul 27, 2012

Thanks for that.

I reckon if I put the Air Suspension on wading mode, I'll be able to reach those without lying directly under the car (just in case the EAS decides to deflate as I crawl under).

Cheers

Saint.V8 · Jul 27, 2012

leave door or the tailgate open to freeze the EAS

aerofabrique · Jul 27, 2012

If its any use...my abs kicks in slightly under any sort moderate to heavy braking, especially on a particular down hill junction near home. The car is heavier than your average family saloon.
Its perhaps also worth remembering the whole braking system can be brand new but it will only be as good as the tyres that grip the road...

merlinpjl · Jul 27, 2012

Tyres - ah yes!

I bought this vehicle about 3 months ago and the tread on the tyres is fine but they are not tyres that I have heard of!

I will be replacing all four tyres within the next month and will be needing some that cope with mainly road use but as I live in a rural area that is prone to snow in winter, I need something that will do that too.

Any suggestions?

aerofabrique · Jul 27, 2012

merlinpjl said:
Tyres - ah yes!

I bought this vehicle about 3 months ago and the tread on the tyres is fine but they are not tyres that I have heard of!

I will be replacing all four tyres within the next month and will be needing some that cope with mainly road use but as I live in a rural area that is prone to snow in winter, I need something that will do that too.

Any suggestions?

Mainly on road - then definitely a road biased tyre such as the Pirellis, Dunlops or Bridgestones, with an M&S marking for winter. More expensive but should last better. Cheaper alternatives available.

All terrains if it's really rural and consider Nokians or Michelin for Winter if the snow is really bad. Plenty of threads in the forum for tyre choices

Whatever you decide make sure they are all the same size and similar tread depths.

mytyres.co.uk is a good check to see what tyres are available in the appropriate size and what sort of price you can expect to pay.

Diesel Do · Jul 27, 2012

Could also be soggy suspension. Wheel doesn't stay in contact like it should and locks up easily causing abs to cut in. Wouldn't tend to do it with slow manoeuvring tho

Datatek · Jul 28, 2012

merlinpjl said:
Tyres - ah yes!

I bought this vehicle about 3 months ago and the tread on the tyres is fine but they are not tyres that I have heard of!

I will be replacing all four tyres within the next month and will be needing some that cope with mainly road use but as I live in a rural area that is prone to snow in winter, I need something that will do that too.

Any suggestions?

Goodyear Wranglers on mine, pretty good and wear well

ABS comes on when I hit a pothole

merlinpjl

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