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Ford Mondeo Hatchback 2l petrol 2001 ABS
As above.

The wheel bearings have an internal magnetic ring which is fragile apparently, and the wheel bearing has to be fitted in the correct way, not the wrong way round, which may be the problem the lad is having as the system worked before a front wheel bearing was replaced "proffesionaly" ?!

The car has had a lit abs light for sometime before we got this car.

Recently whilst checking the system with the wheels in the air and rotating, the connections where disconnected for testing and then refitted. The car back on the deck and ready for a test drive, the abs light was out, but cam back on after driving for say 1/4 mile.

Maybe a bad connection but suspect a deeper fault.

The ABS sensor is non magnetic, unlike our beloved pugs.

Does anyone on here know if the abs sensor is a coil, a hall effect device, or maybe have a diode inside it ?

The Haynes book says look for an output of 1 - 2v when the wheel is rotating.

A resistance/continuity  check of the 2 connectors to the sensor show different ohms values dependant in which way the dmm leads are connected to the sensor. The sensor shows no fluctuation of output, any output or continuity when the wheel is rotated above 5mph.

I have a scope and will test again with that just in case a dmm will not show any output. Both front sensors show very similar resistance check values but are from different manufacturers, Delphi and probably bosch as one is made in Germany.

No hope of getting any info from bosch (they can go a f them selves! ) but maybe Delphi will play ball ??

Help anyone.......
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Thanks tom, see shoutbox.

The Haynes manual does state that the wheel bearing on the front are to be fitted with great care and a particular
way, the black seal inside closer to the abs sensor.........from memory.

The rear wheel bearings are a "unit" bolted on to the hub carrier, with what looks like the same sensor, but will be checking on this........

Will be asking Delphi about the sensors, bocsh can go f them selves.
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Had a reply from Delphi....thanks Delphi.......your much better than crappy bosch..........

Hi Richard

If the magnetic ring is inside the wheel bearing then this is a 2 wire magneto resistive type sensor.

This sensor works by receiving a voltage down 1 wire (normally battery voltage), and modifying the voltage and current back down the other wire.

This modification of voltage is very small (mV) and produces a square wave signal on an oscilloscope.

Because it must receive a voltage to work, disconnecting the sensor may render the supply voltage at 0v (the ECU switches off the power upon open circuit)

The sensor will also not output any signal whilst disconnected.

This can be checked by using an oscilloscope and looking for amperage changes (around 7-14mA change) or voltage change of around 0.1 > 0.2v.

Alternatively a multimeter capable of that level of accuracy.

I hope this helps


Delphi Technical team

so, will get the scope out and set up and we shall see........

So much for the Haynes Book of Lies !
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Have asked if the sensor needs to be earthed via the metal hub and the brass plate and screw/bolt at the bottom of the sensor, will post reply......
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The sensors brass foot plays no part in "earth" of the sensor......thanks philip at delphi technical, bosch, look and learn how to do business!!
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Some progress made as I now have the car full time for MOT work....will post ABS stuff as we make progress..........

It now passes its ABS self test on ign on, meaning all the senors "communicate".......

welding done ok and engine runs ok.......
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If a sensor is disconnected and ign turned on, the sensors "live feed" wire gets nearly 12v then drops to zero, as the fuel priming system works and then turns off.

If sersors all ok and connected ( i made a pair of test wires fitted between the wiring plug and the sensors socket pins, with a central bear section to connect the dmm to ) the live feed reaches battery voltage and stays there, even with engine running, and the abs light goes out after about 3 seconds.

More to come making rear subframe support blocks so can repair/paint rear jacking points and safety first rear wheels off and rotate wheel flanges to test sensor output and compare with the rest, need to set up scope form this as dmm results not conclusive.
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Rear of car now safely up in the air wheel less.

No wonder these cars rust, rear wheel arch plastic liner has a water absorbing inner liner ffs.

No wonder the rear was noisy sounding like bad wheel bearings, that contain the rotation magnet, disc is worse I have ever seen ( apart from an 1100 wedge pad design, wafer thin!! ) !!

Pads ok bu both discs, inner and outer friction surface down to 20% and that was a corrosion layer, will try and post a pic when disc "cleaned off" as the corrosion layer comes off with light taps. A very rough rusty disc....

Checking for square wave output on rears this afo, if it ever stops raining.
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Turns out that one front wheel bearing has no abs output, sensor was swapped for the other side which was all ok but still no output.

The rear wheel bearings where "noisey" again one with no output.

The list of parts needed for a good mot pass was soooooo long and expensive even at trade prices, so we have decided to scrap this car.

Pity as the body was sound apart from the ends of the sills and rear seat belt anchor points, a relatively easy fix, with some new bolts needed for the rear subframe and links, as well as one front wheel bearing, 2 new rear wheel bearings, 2 new rear discs and pads, 2 new front and rear a/r bar links, rear strut upper mounts x 2, front bottom ball joints, a cv boot and some odds and ends like 4 new rear subframe mount cones etc., not to mention a least a pair of tyres for now etc.. The instrument lights dont work also.

I am over it now and in a better mood.  Space free'd soon for the pug, so its doors off and attend to the door looms and locks on her, as well as a winter service.
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The mondy is now making razor blades.........sob sob sob

Have some removed parts that are good all cheap to clear..........starter motor, alternator, fuel rail with injectors, tail lights, tank pump and gauge unit, other stuff as well, any interest, want some bits ?? just ask.
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