ABS and traction lights....

[Neil Clark]

Hi all, my Z3 once in a while flags up a ABS and traction light, its normally after a fast run at 70mph, if you knock around town it wont come on. After a days driving it always go's off. I reckon its just a dirty sensor or ABS ring but which one!?.

The car is a 2000 X plate and has OBC1 and OBC2, ive plugged my code reader into OBC2 under steering wheel and it comes up with no faults, do i need to use the OBC1 port under bonnet?

Cheers all!

Neil

[siwilson]

ABS systems can't be read from the OBD connector. You need to use the one under the bonnet.

If it only gives an error at speed then it sounds like a wheel sensor or perhaps just that the tyres are too different.

Do you have standard wheels and tyre sizes?

[Neil Clark]

ABS systems can't be read from the OBD connector. You need to use the one under the bonnet.

If it only gives an error at speed then it sounds like a wheel sensor or perhaps just that the tyres are too different.

Do you have standard wheels and tyre sizes?

Standard wheels and tyres matey

[Robert T]

Our recent testing has shown that the only module that we can talk to via the OBDII connector in the cabin is the engine - if you want to talk to anything else you need to use the round 20-pin connector under the bonnet - with a 2001 car this may be as simple as using an adapter cable, but I don't know what kind of reader you have - our tests were with the BMTechnic USB cable, adapter and software - take a look at my INPA threads for details.

BTW OBC stands for On-Board Computer in BMW land - you want On-Board Diagnostics - mind you I always want to type ODB (as in ODBC), but that's because I spend far too much of my time working with computers.

Cheers R.

[Jonttt]

Sounds like an intermittent speed sensor fault. A proper diagnostic should tell you which one. It could be the metal ring as you say but much more common to be the sensor.

[Alan W]

I have exactly the same issue, the ABS and ASC coming on together intermittently and it is a right pain in the arse which I can live with but it will obviously causes concerns around MOT time. The previous owner of my car who is a good friend, replaced the rear abs sensors just before he sold it to me as he was having similar issues, but this proved a temporary fix as the problem resurfaced about a week after I bought it. I have had carsoft and bmw diagnostics run on car but cannot find an actual specific fault and was advised to disconnect the plug from the ASC black plastic 'brain' box on the ABS pump and to spray it with some switch cleaner. Havent got round to this but it is on my list of jobs to do whilst the car is garaged for the winter months.

Interesting to read the bit about tyres as I have michelins all round but the newer front ones have a completely different tread pattern, could this realistically be the cause?

[Del]

These lights coming on now and again is commonly caused by dirty/failing sensors or chafed wiring to those sensors – it’s happened to me once in dry sunny conditions. I have seen a post on this forum where the “tracking” being out of adjustment also caused it. Different tyre treads would seem a bit sensitive but I suppose one couldn’t rule it out 100%. Different wheel sizes definitely causes the problem hence the warning in my owners booklet to turn off the system temporarily when fitting the emergency wheel.

[robf]

Hi,I had same problem>>cleaned the sensors and the fault disappeared for a few months then came back with a vengeance.
Fault code 71 via the engine 20 pin connector.A local electrical magician fixed it the same day.He removed the ABS controller and cut of the top of the case (it's welded on) but did not divulge what he had done, other than say he had fixed it.It's been a few months since and all's well.
I took the repair option as it was cheaper than a replacement unit or a 2nd hand one, both of which require the unit to be re programmed for the individual car via BMW which again ramps up the cost.
Cheers rob.

[Southernboy]

FYI. There is a speed sensor fitted to the diff too...it can be seen from the rear if you get down and look on the right hand side of the diff cover. This is driven by magnetic induction. The sensor has two arms which straddle a flat bladed "fan" looking metal wheel attached to the same shaft center as the drive axles. As the diff spins, it passes through the two magnetic arms of the senso, and the speed is relayed to the OBC which then transmits it to the dash speedometer, and possibly other places like the ABS system...worth having a look into the extent of it's influence on the traction controls...

[ZZZ]

Hi,

I have the same problem now, my only hope both lights came on after washing her. My C110 OBD scanner shows as



So may be cleaning sensors will solve the problem but pump is faulty...
There are too many different tips on the forms to take care of the problem.

I will start from fuses and relay unit but is there a link that explains what and where I shall check one by one?

Thx

[Robert T]

The wheel sensors are the usual culprits, and fortunately there are separate error codes for each wheel. Sensors can be dirty, but also check the wiring leading to them - there are flexible sections of harness leading to them and there is a connector which can occasionally get filled with muck. The pump error code cannot distinguish between the pump and the control board and it is more commonly the control board which has problems - if you can do without your car for a week or so, there is a mail order service that will repair them for a reasonable cost.

I have not heard of problems with the diff speed sensor, either causing problems with the speedo or in connection with the ABS/ASC systems - it seems to be very reliable and is not prone to getting dirty. If this sensor was at fault I'd expect an erratic or erroneous speedo reading. I am not sure whether the speedo gauge may be damped (to prevent damage to it if the reading varies wildly), but you can use the odometer self-test mode to get a digital reading of the vehicle speed in km/h - this will be pre-digital to analogue conversion and takes the gauge out of the equation. See the knowledgebase for how to enter self-test mode.

Cheers R.

[ZZZ]

Thanks Robert,

So I will try self test mode, and starting from rear sensors to the point I can reach follow up and clean all the wiring and connections...

The previous owner told me that he replaced one of the abs sensors, and rear tires to pass the MOT. Now I checked I have different brands front and rear

In some forms it says that it might be the problem, after all I may replace the front and rear tires...

I hate to touch OBD, it found a faulty camshaft sensor

[littlefeller]

this is interesting, mine came on after a long run, I parked up and when I came back (about 2 hours later) it had gone, it hasn't come back since but I do have larger wheels than originaly fitted, there also wider and I have different makes on front to rear, why can this cause an abs/tc light?

[ZZZ]

Cleaned the rear Abs sensors and connections, rear right is new and original part, left is old and no name and shape is different... Both are faulty, cleaned up the socket of abs pump... Erased the codes and they are back.... What I feel like is both of the rear sensor can not brake down at the same time, there is something else

Could not find the abs pump relay unit.

Could not unlock the odometer hidden menu, tried both 15 and 19... When I hold it goes back to normal screen....

Rainy dark Dutch night Gonna make donuts in company garden asc is off anway

[ZZZ]

this is interesting, mine came on after a long run, I parked up and when I came back (about 2 hours later) it had gone, it hasn't come back since but I do have larger wheels than originaly fitted, there also wider and I have different makes on front to rear, why can this cause an abs/tc light?

I have 205/50 17 in the front and 225/45 17 at the back... Brands are different but It was ok with those tires. In theory when the diameter is different number, rotation is different, seems like my rear tires turns more then front ones and rear abs sensors reads more but if this is the reason when I reset it with obd scanner lights must go off and should come back when I drive. right?

[littlefeller]

suppose that does make sense, mine are all 16 but I have swapped from 205 to 225 on all four. I suppose some tread patterns could cause a different rolling radius, though this seems unlikely.