Ford Scorpio Forum - Print Page


    
      
        Ford Scorpio Forum
        (https://www.fordscorpio.co.uk/cgi-bin/yabb/YaBB.pl)
      

        General >> Give/Need advice to/from others >> ABS PROBLEMS
        
(Message started by: kittman on Aug 1^st, 2007, 11:57pm)

Title: ABS PROBLEMS
Post by kittman on Aug 1^st, 2007, 11:57pm

I changed an abs sensor that was broken today but still have the abs light on, did an ohms test and don,t know what the results mean. Can anyone shed any light. Front n/s 1150, Front o/s 1135, Rear n/s 1113, Front o/s 1130. thanks. Front n/s was the one I changed.

Title: Re: ABS PROBLEMS
Post by Tompion on Aug 2^nd, 2007, 1:41am

The readings sound OK, I assume you’ve driven the car to go through the test cycle.
I know it says on the site that you need to get the codes cleared if you have a Teves 20 unit, but I’ve not found it to be necessary.
It can save a lot of time if you can get the codes read, I spent ages cleaning connectors sensor rings etc. In the end I bought a lead which showed it was a controller fault.

Dave

Title: Re: ABS PROBLEMS
Post by kittman on Aug 3^rd, 2007, 5:37pm

what test cycle? drove the car about after checking the sensors. I have the older abs unit which should,nt need the codes clearing .

Title: Re: ABS PROBLEMS
Post by kittman on Aug 15^th, 2007, 1:45pm

Today I have changed abs pump/modulator and still have a abs & t/c light on drove the car after and no t/c or abs working I have checked fuses in the batt side fuse box. Is there any relays hiding somewhere that I have,nt seen/checked. Starting to really annoy me now. Can,t find anyone close to read codes yet

Title: Re: ABS PROBLEMS
Post by Tompion on Aug 15^th, 2007, 7:11pm

Was it working before the front sensor needed replacing?

Did you check the resistance of the wheel sensors at the ABS connector - to test all the wiring rather than just the sensor leads?

You can connect the pump motor direct to test that works.

Your new controller could be faulty.

I bought a second hand controller off ebay, which I fitted just to test it. The controller I took off was working fine.
When I had trouble with the ABS a few months later I put back my original “known good controller.” After spending hours checking and cleaning everything, getting it to work for a few miles only to have it go wrong again, I finally bought an ABS test lead to find both controllers had gone wrong with the same failed solder joints.

Title: Re: ABS PROBLEMS
Post by kittman on Aug 15^th, 2007, 7:24pm

No abs was,nt working before I changed the sensor. Call me stupid but how do you check the resistance of the sensors. I,ve taken the pump/controller unit off a donor car that I have and that did,nt have any lights on

Title: Re: ABS PROBLEMS
Post by Tompion on Aug 15^th, 2007, 8:38pm

Have a look at the wiring diagrams here:

http://www.carsoft.ru/avtorepair/sierra_el.html

On page 2 of the ABS/TCS PDF you can see the pin numbers and wire colours at the connector, unplug it and test with a meter between the relevant pins same as you did when you tested the sensors - you should get similar ohm readings.

You should be able to see the pin numbers on the plug (at least you can on the teves 20, I assume you can on yours)
If I’ve copied it right:
Pins 9, 10 LH rear
Pins 11, 12 RH rear
Pins 5, 6 LH front
Pins 7, 8 RH front

Title: Re: ABS PROBLEMS
Post by kittman on Aug 15^th, 2007, 10:28pm

Cheers tompion i,ll have a look tomorrow to see what I can find!

Title: Re: ABS PROBLEMS
Post by harry.m1byt on Aug 17^th, 2007, 9:51pm

on 08/15/07 at 19:24:19, kittman wrote:

You check the sensors by simply measuring the resistance across the two terminal pins nearest the wheels, as you seem to have done. Those readings you gave were in the correct range for good sensors. You might also confirm that the wiring is good for the sensors by checking for the same sort of resistance at the ABS unit.

Even if the readings are correct it is only an indication that the sensors are probably OK - it does not guarantee that they are.

Your ABS controller checks these resistance values are correct when you switch the ignition on, if the ABS light goes out it means they are correct. These along with its internal controller tests, are its static tests.

When you drive off and first hit 15mph the unit then carries out its further tests to prove that signals from the sensors are within sensible ranges - if not it will put the ABS warning light back on at this speed. Even a low tyre pressure can cause it to come on.

So if it comes back on at 15mph - check tyre pressures, check the sensors disk is free of debris and that there are no cracks or damge to them. A diagnostics system would be able to provide details of which wheel sensor is providing an incorrect reading.

An oscilloscope could be used as an alternative, if connected to each sensor in turn then spinning the associated wheel - You should see a waveform which is reasonably regular and symetrical with no strange glitches from each circuit.

The sensor basically generates an AC waveform, with a pulse as each tooth of the toothed wheel passes the head. The sensor head is simply a coil of very thin wire wound round a former, having a voltage induced in it by the teeth as they go past it.

Moisture entering the exposed front connectors of the sensors can also cause the ABS light to come on at 15mph. I had this problem during the heavy rain a few weeks ago.

Hope that provides you with some clues?