Porsche Enthusiasts Club Forum

I have had a previous thread on this subject.

Since August 2008 my ABS warning light has been coming on once I go over 20mph. When changing the front discs and pads I took the sensors out and cleaned them. I was able to push them out from the inside seeing as I had the discs off. I am now trying to remove the rear ones to clean them, but this time I am not removing the discs.

Has anybody got any tips of an easy way to get them out once the bolt has been removed? At the moment it's soaking in WD40.

Thanks for help on this.

This weekend's other job is to put a new rear subframe on the Mini. If I look on the notice board in my garage it says that I put the car on axle stands on 06 10 2007 - no rush then! I've got all the bits just sat here, so it'll be done this weekend so that it can be MOTd and we can use it as a run-around. I really can have one of those stickers in the back window that says 'My other car's a Porsche'.

Try carefully twisting the sensors, that how we used to do it on Fords.

Have you checked the wheel bearings or tyre sizes?

07 Thats not bad I started to restore my 1275GT in 2003 and have not touched it in 4 years.

Come to think of it I have not seen it in 3 years

Just needed lots of WD40 and patience.... rather than the big hammer. Got them out, cleaned them, refitted then test drive - and the light's still coming on once the car is moving. Jacked up the front off-side, started the engine and manually spun the wheel until the light came on - I believe the light should come on because the wheel I am spinning is +/- 6% of the speed of the three static wheels. I also put an AVO on to the sensors and they show resistance - I think that if they are duff they show open circuit. Did the same with the near-side, and the light came on. Did the same with the rear off-side and the light didn't come on. Then my neighbour (age 40) and myself (age 50) were called in by our wives for tea!! I have had to put it all away until the morning, but at the moment expect to find that the rear near-side will turn the light on and the off-side rear sensor will show open circuit - can't wait until I'm allowed out again in the morning.

If anybody disagrees with my theory please let me know before I go too far.

And the Mini has to wait until I've finished the Porsche.

What your saying sounds about right.

Each sensor should produce a very small voltage 0.5 to maybe 2.0 volt when you spin the wheel, put a voltmeter across the sensor and spin the wheel.

Depends on the sensor, some are really only testable by an oscilloscope. It sounds like the sensor has failed, I'd have thought a good s/h one should be available.

The rear near-side one was open circuit, so I replaced it with a brand new one. However turning either back wheel does not make the light come on as I would expect, yet I still have the fault light showing on the dashboard once I start driving the car.

Any ideas?

Hi John

I had a similar problem on my 928...

You need to find the ABS box and test the terminals for each sensor there...

I did this and it told me WHICH it was, I had already done all you have and it was driving me nuts...

In my case it was front right.....so I had to remove the WHOLE SENSOR AND WIRE all the way through the inner wing ...

Once it was all out INCLUDING the wire. I found a break in the insulation where it had rubbed around 5 inches from the sensor.....when I twisted the break open.... the wires inside were corroded and shorting across each other....those wires are MEANT to be clipped to various suspension parts before going onto inner wing.....my ones had the small plastic holders broken over the years and therefore rubbed

So new sensor AND complete wire that comes attached and finally cured.....

928 Sensor and wire was around £80

But around a week later a guy with no brake lights did an emergency stop in front of me in the rain......and it was ONLY my ABS that stopped me ramming into back of him, so worth while doing

All the best Brett

Thank you Brett, very useful. That's Saturday's job then. Being an electronics engineer by trade (although I haven't done it for 20 years as there's not much call for installing radar systems in our street, or those big aerials like I put up on Windy Ridge and Sappers Hill in the Falklands) I had a suspicion it must be something to do with only the back half of the system, and therefore could be wiring. In the 944 the ABS box is under the dash by the driver's right knee, so easily accessible. Sunday's job is to sort out the vibration on the camshafts as per the other thread.

I shall update with the results of the ABS problem over the weekend.

The sensors do not produce voltage, they are a 2 wire inductive sensors.
When there is metal - a gear tooth in this case they will switch to ground (battery -ve).

You probably have a brown wire bolted to each strut? If so make sure this wire is not broken and there is a good rust free connection.

Sensors can be tested with a dvm or osc scope.

Rich

How lazy can one be! Three years with this problem and I have just cured it this afternoon using a used rear off-side ABS sensor (cost about £5) and thirty minutes of my time. I knew all the time that it was a sensor, should have changed both rears when I did the near-side one.

That's just so embarrasing

Consider myself told off.