Porsche Enthusiasts Club Forum

204571 miles and sailed through again. I'm sure if you look after these cars they will last forever, and the style will never go out of fashion - not in my eyes anyway

Controversial point - ABS light..... I know a few people have queried this....

My ABS light has been on for a couple of years now. It was on at last year's MOT and the previous years too. Start the engine and the light does not come on. Get to about 20 mph and it comes on. I park up outside the MOT bay, turn the engine off and hand the keys over to the tester. He drives into the bay, but not fast enough to turn the light on, and puts the car onto the rollers. He then does all the tests on the brakes, both front wheels at once, both rear wheels at once, and all individually. The light doesn't illuminate, yet I suspect the rollers are doing more than 20 mph while he tests the brakes. He then moves onto the ramp and does the rest of the MOT... and as usual it passes.

I do want the problem sorting out, so is there a plug-in diagnostic thing that can be done?

Thank you.

It sounds like a wheel speed sensor.
i have the non abs car....

Dissconect the sensor at each wheel and check for damage first.
2nd, check continuity in the circuit.
3rd, if all else fails, get a diagnostic done!

Certainly sounds like a wheel sensor although I thought they self tested at 8mph.
I don't think the diagnostics are good enough on 944s to check the ABS but there is a Porsche brochure on testing the ABS system - occasionally they pop up on ebay.
Certainly the indie who fixed my ABS had some sort of electronic gadgetery that helped.
If you're really clever you can use an oscilloscope to check the electrical circuitry. I'm not.


At 204 K you're catching me up - must get my new tyres on and do some miles!

Is it actually faulty or is it a computer glitch?

Find a quiet carpark and brake hard from 25 mph. If you manage to lock a wheel then you know you have a real world problem. As others have pointed out a wheel sensor is then the likely culprit. If you do manage to lock a wheel then you need to keep the car off the road until it is sorted as if you were involved in a collision with another person then you would likely find yourself uninsured and looking at being nicked for driving an unroadworthy vehicle.

I think you will find the statement above to be incorrect. One's insurance policy insure's one to drive one's vehicle irrelevant of it's road-worthiness. That is the risk that the insurance company takes - having a MOT only becomes relevant when one makes a claim for one's own vehicle as it affects the value of the car. My car does have a brand new MOT - although in reality an MOT only means that the car was road worthy for the hour it was in testing.

I am going to check all the sensors for a signal with my Fluke meter at the weekend. If I can't find a faulty one I will disconnect all the sensors and see what happens. The answer should be that the light comes on before the car moves because the system doesn't pass initial checks because I have caused an open-circuit in the system. At the moment the system passes initial checks because the light goes out after the car is started, only coming on again at about 20 mph - hopefully because a sensor is not sending a signal. If I can't fix it I'll take it in to be checked by an expert.

I'll nip down the local supermarket car-park now while I'm out and try out your simple test..... if it's safe to do so. Actually, I live on a country lane, I can just do it outside here! Either way I'll wait until the roads are dry - I'm not very good in the wet or ice

I think you will find it isn't.

If you knowingly, persistently drive a dangerously defective vehicle on the road, good luck persuading any insurance company to pay out in the event of a claim – feel free to test the water, though. No insurance company is going to pay out on a car that was in contravention of the road and traffic act before an incident.
The law is quite clear on this issue. Using a vehicle with defective ABS when fitted is a contravention of construction and use and therefore a contravention of the road and traffic act.
Ssection 40a of the road and traffic act of 1988 states:

"40A Using vehicle in dangerous condition etc. E+W+S.A person is guilty of an offence if he uses, or causes or permits another to use, a motor vehicle or trailer on a road when—

(a)the condition of the motor vehicle or trailer, or of its accessories or equipment, or
(b)the purpose for which it is used, or
(c)the number of passengers carried by it, or the manner in which they are carried, or
(d)the weight, position or distribution of its load, or the manner in which it is secured,
is such that the use of the motor vehicle or trailer involves a danger of injury to any person



Insurance issues aside, I recall an incident where a Ford Scorpio did not see a traffic light on red. A pedestrian walked out and the driver slammed on the brakes. The car locked up and a big cloud of tyre smoke enveloped the car. The car just caught the young woman but fortuitously she was uninjured. This whole incident was recorded on police CCTV. The driver was prosecuted for careless driving. He was also prosecuted for driving a vehicle in an unroadworthy condition, contravening the terms of construction and use of equipment as the pc who viewed the footage realised the ford should have ABS fitted. He ended up with 6 points and a big fine.

I am good friends with Roche Bentley, former CEO of Lancaster insurance. I would be more than happy to drop him a line and ask him whether his company would pay out if it could be proven that the owner knowingly drove round in a vehicle in direct contravention of section 40A .