ABS Light on

[dickens]

Hi Guys
Problem started a few days ago came to a junction and it felt like the ABS had come on grating noise at front of car. Carried on like that for a while then the ABS light came on and braking seemed normal. Spent all day today visually checking cables all seemed ok.(speedo is working ok). So if there is an issue with one of the sensors how do you know which one.

[rover54]

Was the brake peddle pulsing as you came to a halt or at anytime when you applied the brakes?
Does the ABS light go out when you start the car and does it come on when you start driving?
Does it stay on all the time?
Do you have cruise control and is it working?

[StevenWilliams]

the quickest way to test each one is to use a T4.

For me it was quite easy to identify as a sensor cable had sheered. What I will say is that you have to be really careful when reconnecting the blue connectors if you removed them as they often will not seat properly again.

I used a continuity connector and tested each connection to find the fault.

[HarryM1BYT]

Originally Posted by dickens

Hi Guys
Problem started a few days ago came to a junction and it felt like the ABS had come on grating noise at front of car. Carried on like that for a while then the ABS light came on and braking seemed normal. Spent all day today visually checking cables all seemed ok.(speedo is working ok). So if there is an issue with one of the sensors how do you know which one.

Disabling the ABS (ABS light on) is the normal ABS systems reaction to a fault. You then have no ABS, so no more judder at the pedal.

As per Rover54's reply, those questions need to be answered before further help can be given.

Assuming one sensor has failed completely, as in light staying on once ignition is turned on - you could try substitution. Plug a known to be good sensor into the socket at each wheel in turn and try the ignition on test, for each wheel in turn. If you get the light to go out, then you have found the failed sensor.

But there are other modes of failure..

[oliver123456]

Originally Posted by dickens

Hi Guys
Problem started a few days ago came to a junction and it felt like the ABS had come on grating noise at front of car. Carried on like that for a while then the ABS light came on and braking seemed normal. Spent all day today visually checking cables all seemed ok.(speedo is working ok). So if there is an issue with one of the sensors how do you know which one.

Hi, had the same problem, check at e-bay germany, cost 32 Euro, easy to change! in and out.....have fun made

[rover54]

Originally Posted by oliver123456

Hi, had the same problem, check at e-bay germany, cost 32 Euro, easy to change! in and out.....have fun made

Changing ABS sensors is not fun, mostly they are stick in and you have to drill them out and hoping you don't damage the hub bearing in doing so. You must have been lucky or somebody must have changed it not long ago.

Pulsating brake peddle might be the hub bearing ferro magnetic ring not triggering the sensor correctly, with the ABS thinking the wheel is locking up.

[dickens]

Originally Posted by rover54

Was the brake peddle pulsing as you came to a halt or at anytime when you applied the brakes?
Does the ABS light go out when you start the car and does it come on when you start driving?
Does it stay on all the time?
Do you have cruise control and is it working?

Hi
Update on ABS probs
when you turn on the ignition abs light comes on as normal and goes out when car is started. Initially when driving the pedal judders at junctions as if the abs is doing what it should do on a skid. However after a short while a message comes up on the electronic screen saying abs fault then the abs comes on and stays on. The brakes then work normally. This evening a red message came up say ing brake fault so i stopped and re started the car and that went out

[dickens]

Originally Posted by rover54

Was the brake peddle pulsing as you came to a halt or at anytime when you applied the brakes?
Does the ABS light go out when you start the car and does it come on when you start driving?
Does it stay on all the time?
Do you have cruise control and is it working?

sorry meant to say dont have cruise control

[rover54]

As the ASB light goes out when you start the car, the ABS sensors pass the self test. One theory for pulsating brake peddles is the ferro magnetic wheel bearing which the ABS sensor uses to detect wheel rotation become defective and an incorrect speed signal is received by the ABS unit and therefore thinks one of the wheels is locking, hence activation of ABS with a pulsing brake peddle.

I think the next thing you need to do is have the car T4 by either one of the guys on this forum, or a garage so equiped.

ABS problems can be a bit of a nightmare to detect and rectify and if a T4 doesn't show any electrical problem, then you need to investgate the hub bearings.

Some people have found a problem with corroded wiring in the plug on the ABS unit (under the battery box), but I think you have a dynamic problem, therefore the issue is at one of the wheels.

[HarryM1BYT]

Originally Posted by rover54

As the ASB light goes out when you start the car, the ABS sensors pass the self test. One theory for pulsating brake peddles is the ferro magnetic wheel bearing which the ABS sensor uses to detect wheel rotation become defective and an incorrect speed signal is received by the ABS unit and therefore thinks one of the wheels is locking, hence activation of ABS with a pulsing brake peddle.

I think the next thing you need to do is have the car T4 by either one of the guys on this forum, or a garage so equiped.

ABS problems can be a bit of a nightmare to detect and rectify and if a T4 doesn't show any electrical problem, then you need to investgate the hub bearings.

Some people have found a problem with corroded wiring in the plug on the ABS unit (under the battery box), but I think you have a dynamic problem, therefore the issue is at one of the wheels.

I agree with the 'dynamic issue', except that as the issue seems to be triggered by actual braking, I would suggest it might be due to suspension and /or wheels. Check for suspension play, wheel bearing play, track rod play, tyre pressures and etc..