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        General >> Give/Need advice to/from others >> ABS Light
        
(Message started by: philgood on Mar 24^th, 2008, 11:56am)

Title: ABS Light
Post by philgood on Mar 24^th, 2008, 11:56am

For several weeks now my ABS light comes on with the ignition lights and stays on ???

How do I know which sensor is at fault?

Can anyone tell me what to check first & if there is a sequence of checking the wheel/brake sensors?

Regards

Phil

Title: Re: ABS Light
Post by harry.m1byt on Mar 24^th, 2008, 12:27pm

Hi Phil,

There are two functional places for it to fail...

1. When the ignition is turned on it carries out static tests. If it fails it will stay on all the time.
2. Once speed rises above 15mph it carries out dynamic tests. If it fails, it will go out at stage 1, then come back on at >15mph.

If yours goes on with the ignition and remains on, it is failing at stage 1.

Stage one checks out the basics of the ABS controller and the wheel sensors. Most likely it will be a wheel sensor at fault. Check the resistance across the two connections of each sensor, they should be slightly more than 1,000Ohms each. The connection points at the front are on the inner wing, just behind the top of the tyre (out in all the muck) and at the rear under the rear seat. Most likely it will be corrosion at the connections causing high resistance, which can be cleaned off.

Title: Re: ABS Light
Post by philgood on Mar 24^th, 2008, 10:19pm

Thanks Harry
That’s the sort of information I needed. I'll check out the sensors in the next couple of days and post the results. If I find one at fault does any one know the price of a replacement?
Regards
Phil

Title: Re: ABS Light
Post by philgood on Mar 25^th, 2008, 1:14pm

Ok

All sensors check out ok (1000 + Ohm each). Connector plugs seem clean, no corrosion, dirt or damage and still has water proof grease in them. Checked multi plug at modulator with no problem found. Check ABS light after each stage and it’s still on! Any other thoughts from any one!!

Title: Re: ABS Light
Post by Tompion on Mar 25^th, 2008, 3:02pm

Have you looked here and checked fuses listed:
http://www.fordscorpio.co.uk/abssystem.htm

Look under the heading connections, there is another connection on some earlier cars.

Title: Re: ABS Light
Post by philgood on Mar 25^th, 2008, 3:04pm

Right.
Started the car up & the ABS light stayed on until I drove the car 100yds to put it away in my garage, and the ABS light went out!! But on closer inspection it was still very slightly illuminated.
Turned the engine off and then turned on the ignition on again with the same result, the light seems to go out but noticed it was still on but very, very dim. It would be good enough to pass an MOT.
I’m confident that the fuse boxes are ok but there must be a short/earth fault somewhere as I have had electrical problems in the past causing my brake lights to stay on, see my other post (what’s this relay thingy I disconnected).
Looks like a big job, I’ll have to work my way through the complete electrical system. Is there any fault diagnostics I could use to help? As I’ve heard of connecting a lap top some how to vehicle.

Title: Re: ABS Light
Post by Tompion on Mar 25^th, 2008, 6:57pm

Could be an earthing fault somewhere, I'd clean all the earth points if it was mine.

Title: Re: ABS Light
Post by davem on Mar 28^th, 2008, 12:02pm

Also check the connector to the ABS pump. On my Scorp the wires in the plug had corroded and this lead to the ABS light on almost all the time.
This connector can be found under the bonnet, driver's side and has a bolt holding the connector onto the ABS pump. Remove the bolt, remove the plug, remove the plastic cover and examine all the wires.

Title: Re: ABS Light
Post by Tons_of_fun on Mar 28^th, 2008, 4:41pm

Hi harry.That info was interesting.Just wondering what were the common causes of abs light coming on at & above 15 mph ?.I have recently aquired an mot failed 2.9 12v which was sold to me with an abs fault (very cheaply ;)).As far as i can tell the only problem is the light coming on above 15 mph.

Title: Re: ABS Light
Post by TiberiuS on Mar 28^th, 2008, 6:51pm

Tonnes, I did a lot of searching on this when I had the problem. The norm (at least with the older Teves unit) seems to be when the light is on constantly it's a short or open circuit wheel sensor (or damaged loom etc), when you get a dynamic fault where it stays off until 15mph is the time when it's often a fault inside the ECU (as mine was).

Also had this in the Jag (same unit as the Scorp) and it was the same fault, same cause..

Both mine had missing lamps, both failed the MOT when it was picked up by the tester, both showed ABS fault at 15mph once lamp/LED replaced. The Scorp was due back in the dealer for new hubs/brakes and failed the MOT anyway but I got it reconditioned myself, dealer price for new pump/ECU is not for the faint hearted :o

I have a photo of inside my Scorpio Teves, I pulled it apart but faced with the resin coated board I sent it away to be sorted, my loss, less hassle etc..

First time it was a puzzle, second time it was just pull the plug and check the sensor coils were intact and then pull the unit for recon. I didn't get as far with the faultfinding as Tompion, not sure if they fail in the same place but it seems the board in the earlier version was a tight fit in the case and some of the tracks/joints tended to break with the heat and movement.

Hope this helps.

Regards, Bruce.

Title: Re: ABS Light
Post by Tons_of_fun on Apr 2^nd, 2008, 10:23pm

Thanks Bruce.Pulled the plug off the abs pump & give it a darn good soaking with contact cleaner ,then wd40.Still comes on after 15mph so i guess i have a bit more digging to do :-/.Oh well,thats what the weekends were made for ;D

Title: Re: ABS Light
Post by sector-9 on Apr 3^rd, 2008, 11:09pm

Check the reluctor rings that the wheel sensors aim at. If they're cracked, broken teeth or even excessive corrosion/dirt/etc. then this can cause a poor or erratic signal which the ECU would notice. Of course, this fault wouldn't occur with the vehicle stationary!
If you've got access to an oscilloscope then this could make diagnosing each sensor much easier. Finally, check the tyre pressures to make sure they're all broadly similar and the same size tyres as it has been known for different rotational velocities to trigger an ABS fault.

Darren

Title: Re: ABS Light
Post by harry.m1byt on Apr 5^th, 2008, 9:33am

on 03/28/08 at 16:41:00, Tons_of_fun wrote:

Hi harry.That info was interesting.Just wondering what were the common causes of abs light coming on at & above 15 mph ?.

Sorry for the delays, my broadband has been off for upgrade...

Ignoring possible problems with the ABS controller. The light coming on immediately above 15mph, would mean..

1. Cracked cogged wheel, or metallic dirt in the cogs.

2. Possible a failing bearing (rear).

3. A faulty sensor (despite it measuring 1000 Ohms).

4. An odd wheel or odd tyre pressures.

If the light doesn't come on in a predictable way at exactly 15mph - then I would be looking for some intermitant connection to a wheel sensor. Mine started doing this in the rain and I traced it to a poor connection behind a front wheel, the one in the mudguard.

Title: Re: ABS Light
Post by Tons_of_fun on Apr 5^th, 2008, 11:48am

Thanks fellas.ABS problem is on hold at the moment as im having what can only be described as "Catastrophic electrical failure" :'(.At the moment you cant see the car for electrical wires !!! TBH it,s not looking promising but will let you know the outcome.Thanks again.....Craig :)