TCS Coming on for no reason

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z3d
Joined: Wed 22 Apr, 2015 20:48
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  Z3 roadster 2.8

TCS Coming on for no reason

Post by z3d » Mon 07 Sep, 2015 21:32

Hi all,

I'm in desperate need of some help.. The passed 2 or 3 days i have an issue which today became dangerous. Basically when i accelerate in my car once i reach higher speeds of anywhere between 65 and 100 mph (On private roads obviously ;) ) The TCS cuts my power and does not allow me to accelerate any further. Today i was overtaking someone and it happened, luckily i was quick enough to hit my TCS button to let my engine rev freely again to complete the overtake. But on another day that could have had a different outcome.

It is also extra extra sensitive when going around corners now and tcs cuts my power when going round very reasonable corners at very reasonable speed. Nothing excessive..

I have no idea what is happening or why its happening. Its not something ive ever came across before on forums or other peoples experiences. I really hope someone can help me out here.

Kind regards Josh

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Brian H
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Re: TCS Coming on for no reason

Post by Brian H » Mon 07 Sep, 2015 22:37

Hi Josh,

There is a reason the TCS is coming on, we just need to work out why? What car do you have, year and model?

Cheers

Brian

z3d
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by z3d » Mon 07 Sep, 2015 22:40

Its a P reg 1997 2.8 z3. Done around 110k miles and has been running perfect for over a year now. I took it in for two new front tyres and then coincidentally this has happened ever since..

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stevov
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Re: TCS Coming on for no reason

Post by stevov » Tue 08 Sep, 2015 07:03

The timing of this occurring would suggest the possibility of one of the front abs sensors at fault. Is it just the TCS light coming on. Are the tyres the correct size. Can you get the car checked for codes.

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BladeRunner919
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  Z3 roadster 1.9

Re: TCS Coming on for no reason

Post by BladeRunner919 » Tue 08 Sep, 2015 08:52

Also check tyre pressures in case one is very low and giving a different rotational speed.

Hairyscreech
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by Hairyscreech » Tue 08 Sep, 2015 09:18

You don't have 3 new and one very worn tyre do you? That can be enough to do this.

Are your tyre sizes and profiles correct on all wheels, do you have standard wheels/tyre sizes for your car on?

Are your wheel speed sensors and trigger rings all ok and not dirty/corroded?

Del
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  Z3 roadster 1.9

Re: TCS Coming on for no reason

Post by Del » Tue 08 Sep, 2015 09:32

As said already, it is a suspicious coincidence that this happened immediately after fitting new tyres. Any tiny difference in rotational speed will be picked up by wheel sensors - this is why the handbook recommends, for example, turning off these systems when fitting the temporary space saver spare wheel. As said above, if it isn't a tyre issue the car needs to get plugged into a error code reader to pinpoint any faulty wheel sensor.

z3d
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by z3d » Tue 08 Sep, 2015 09:38

It is 2 front tyres that i had, the rear ones are still the same as before but will be replaced wthin 6 months anyway.

I will try and find somewhere to get it plugged in, do a lot of garages have the ability to check my error codes or do i need a specialist?

Based in Cannock, West Midlands if anyone knows anywhere decent to go.

Or, whats the best code reader to buy? Mines a 1997 so unsure whether odb1 or 2

siwilson
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Re: TCS Coming on for no reason

Post by siwilson » Tue 08 Sep, 2015 10:15

One thing that might have escaped people here is that this car does not have DSC fitted, only ASC+T. This means the only regulation is to reduce power and brake the rear when wheel spin is detected. It does this by sensing that the rear wheels are spinning faster than the fronts. If one rear wheel spins faster is pulses the brake for that wheel. If both rear wheels spin faster it reduces engine power.

What size tyres do you have on all 4 corners now and what were they before the change?

I don't know if there is a calibration for new tyres like on a DSC system, but if there is you might want to try it.
Last edited by siwilson on Tue 08 Sep, 2015 15:48, edited 1 time in total.
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z3d
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by z3d » Tue 08 Sep, 2015 10:46

Rears which havent changed tyres are 245/40/17
And Fronts which tyres have changed but are the size they used to be are 225/45/17

Standard wheels and i think standard tyre sizes..

Del
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  Z3 roadster 1.9

Re: TCS Coming on for no reason

Post by Del » Tue 08 Sep, 2015 10:50

z3d wrote:Or, whats the best code reader to buy? Mines a 1997 so unsure whether odb1 or 2
I believe you need BMW specific INPA to pinpoint a faulty wheel sensor

z3d
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by z3d » Tue 08 Sep, 2015 11:12

Del wrote:I believe you need BMW specific INPA to pinpoint a faulty wheel sensor
Right ok, is there anywhere specific to buy this from or is it an ebay joby?

Mike Fishwick
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  Z3 roadster 2.8
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Re: TCS Coming on for no reason

Post by Mike Fishwick » Tue 08 Sep, 2015 11:16

Why not try a bit of DIY?

What are the tread depths of each tyre?

Have you removed the front wheels yourself, and checked that the sensor cables are not damaged?

Have you removed the sensors and made sure they are clean?
A Z3 is not just for Christmas - it's for life!

z3d
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by z3d » Tue 08 Sep, 2015 11:55

Mike Fishwick wrote:Why not try a bit of DIY?

What are the tread depths of each tyre?

Have you removed the front wheels yourself, and checked that the sensor cables are not damaged?

Have you removed the sensors and made sure they are clean?
I will have to try and look at a few things this weekend.. Are these parts easy enough to look for with the wheels off?

Hairyscreech
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by Hairyscreech » Tue 08 Sep, 2015 13:56

The sensors are only hall effect sensors, unplug them and check the resistance, then check the resistance changes when the hub is turned. Edit - Should be about 1000 Ohms. (1KOhm)

Not sure what the correct resistance for a z3 sensor is but you should be able to compare front to rear and L to R to get an idea if one is out, you will not be able to check the actual signal output but you will see a change in the resistance of the sensor as the teeth of the abs wheel pass the sensor (when the hub is turned).

You don't even need to take the wheel off or turn the ignition on to do this, just jack the wheel you are checking.

To read the ABS fault codes you do indeed need an INPA set up.

As noted above the ASC reduces power when the rears are sponning faster than the fronts, there's a big clue.
If you have new fronts and old rears it's possible your near the limit of the difference allowed before power is reduced, it will only take a little slip on a gear change to activate it if so. Tread on a tyre can have a big effect, when you consider the diameter of the tyre could be reduced by 12mm or even 16mm for a winter tyre. A new tyre and an old one on the same axle can be enough to cause ABS issues.

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Alfie
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Re: TCS Coming on for no reason

Post by Alfie » Tue 08 Sep, 2015 17:09

:idea: Replace your rears with the same brand, type and tread pattern as your new fronts. :idea:
I'm pretty sure your troubles will disappear straight away....
The Z3 is a fickle beast and is known to misbehave if you mix tyres.

A.
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z3d
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by z3d » Tue 08 Sep, 2015 17:22

Hairyscreech wrote:As noted above the ASC reduces power when the rears are sponning faster than the fronts, there's a big clue.
If you have new fronts and old rears it's possible your near the limit of the difference allowed before power is reduced, it will only take a little slip on a gear change to activate it if so. Tread on a tyre can have a big effect, when you consider the diameter of the tyre could be reduced by 12mm or even 16mm for a winter tyre. A new tyre and an old one on the same axle can be enough to cause ABS issues.
Alfie wrote::idea: Replace your rears with the same brand, type and tread pattern as your new fronts. :idea:
I'm pretty sure your troubles will disappear straight away....
The Z3 is a fickle beast and is known to misbehave if you mix tyres.

A.
I will consider doing this after checking a few sensors etc. My rear tyres actually look like they have plenty left. Like around 4-5mm left on them.

Also for me getting an INPA setup will require more research, typically every car i own is always on some kind of crossover from new to old. And its no differnet here, so i need to see what connectors i have first and then look for a decent INPa setup to buy. Am i right in believing i need an old laptop with serial com port on my machine to read the data sent back from the plug?

siwilson
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Re: TCS Coming on for no reason

Post by siwilson » Tue 08 Sep, 2015 18:21

z3d wrote:Rears which havent changed tyres are 245/40/17
And Fronts which tyres have changed but are the size they used to be are 225/45/17

Standard wheels and i think standard tyre sizes..
Just a point on this. 225/45/17 and 245/40/17 is a standard staggered setup on the Z3 so should be OK. However, the same marked size (225/45/17) can differ quite a lot between two different tyre manufactureres. What make model do you have front and rear now?

I suffered for a long while with DSC issues due to non matching tyres and mine were the same make and model, just a mark 1 versus mark a 2 tyre!
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Dino D
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by Dino D » Tue 08 Sep, 2015 18:40

Just to give the other side of the coin, my 98 model with ASC is fine with different brands/sizes across the same axle and I've had a mix of 16/17/18's on the car at the same time (across the same axle).
It didn't like the space saver on the rear of course and needed to be switched off.
As pointed out already the ASC is less complex than the DSC in that it works on the rear only so I wouldn't expect new fronts to cause an issue.
Just yesterday I put my 17's with new tyres on the front and have my work 18's on the rear and no ASC issues.

Del
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  Z3 roadster 1.9

Re: TCS Coming on for no reason

Post by Del » Tue 08 Sep, 2015 19:09

Dino D wrote:Just yesterday I put my 17's with new tyres on the front and have my work 18's on the rear and no ASC issues.
Bit surprised you had different diameter wheels with no problem :shock:
Agree that the ASC+T applies itself only on the rear, drive wheels. However, my understanding is that the measurement the ECU takes (to determine whether a rear wheel is spinning) is made with reference to the front wheel. If the system detects a single rear wheel is spinning it will apply the ABS system to that spinning rear wheel (similar result to a LSD). If it detects that both rear wheels are spinning (logically it can only do this with reference to the front wheels) then it can also reduce engine torque.

Dino D
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by Dino D » Tue 08 Sep, 2015 21:52

Del wrote:
Dino D wrote:Just yesterday I put my 17's with new tyres on the front and have my work 18's on the rear and no ASC issues.
Bit surprised you had different diameter wheels with no problem :shock:
The overall diameter is quite close between the 17's and 18's though as the profile is lower on the 18's so not as big as you may have been thinking!

I've seen Z's on the U.S. forums with increased profile rears compare with normal and the guys report no ASC issues (I'm talking of 45 instead of 40 or 40 instead of 35, so not massive difference but enough to be visible)

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Alfie
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Re: TCS Coming on for no reason

Post by Alfie » Wed 09 Sep, 2015 00:57

z3d wrote:My rear tyres actually look like they have plenty left. Like around 4-5mm left on them.
The amount of wear isn't the issue.
I suggest you replace the rears to match the tread pattern of the fronts and keep your old part-worns so you can re-fit them if the new tyres don't fix the problem....

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Hairyscreech
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by Hairyscreech » Wed 09 Sep, 2015 09:17

I guess the big question here is, did the car start life with a non-staggered setup. i.e. the 225/45/17 on both axles?

As fitting the staggered 225/45/17 and 245/40/17 will change the expected wheel speeds. The staggered setup mean the rears actually rotate 1% faster when the car is coasting, Acceleration will increase the amount of difference as tyres are actually slightly slipping all the time (hence they wear).

I don't think increased profiles will cause a problem as the rears will be rotating slower than the fronts by nature of their larger size, it's smaller and faster that's the issue. I suspect the US guys with larger rears on will have a delayed activation point when their wheels spin.

Del
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  Z3 roadster 1.9

Re: TCS Coming on for no reason

Post by Del » Wed 09 Sep, 2015 10:36

As the car is question is a z3 2.8 and assuming it has approved BMW wheels (7.5JX17 front and 8.5JX17 rear) the approved, staggered tyre set up is front 225/45X17 and rear 245/40X17).

The only comments I have seen about standard BMWs (E36 and E36/7s) are that the ASC system can be sensitive to tyres which to not comply with the dimensions above.

If the ASC+T light is flashing (as opposed to being on all the time) it suggests it is working properly.

The ASC +T light only flashes when it is in the phase of cutting engine power.

At speeds above 62 mph, the ABS phase of the ASC+T system does not operate for safety reasons.

On the face of it, it looks like your ASC+T system thinks (since having new tyres fitted) and at higher speeds, that your front wheels are rotating unnaturally slower than the rears i.e. that the rear axle is losing traction.

Simple, practical things to check would be tyres pressures, do you suspect the “tracking” is significantly out at the front i.e. was the reason for replacement uneven tyre wear? Is there a sticky brake calliper at the front – this tends to get worse at higher speeds and if so, a wheel will get noticeably hot?

Hairyscreech
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by Hairyscreech » Wed 09 Sep, 2015 11:09

In that case if it is a 2.8 car it is likely ASC+T as you say but not all 2.8s had the staggered set up.
The car as standard could have come with either a "square" set up or staggered depending on what the customer requested, I saw one the other day with the square setup and it looked a bit odd to be honest.
The VIN decoder will come up with the option "299 LT/ALY WHEELS W MIXED TYRES" if it came with staggered tyres from the factory.

Does anyone know if there is a calibration value that can be set in the ABS ecu (via INPA or similar) to account for this kind of thing?
Assuming someone wanted to run drastically different wheel sizes or to temporarily correct a situation like the OP has?

z3d
Joined: Wed 22 Apr, 2015 20:48
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  Z3 roadster 2.8

Re: TCS Coming on for no reason

Post by z3d » Wed 09 Sep, 2015 14:08

Just to clarify a few more comments on here, My car (the 2.8) did originally have the staggered set up. I will spend a little money on the car over the coming weeks, such as tracking, and new tyres for the rear. I will ensure i purchase the same make and the correct size, then the rolling dimensions should be good.

As for the comment about the ABS sensor for detecting speeds etc, its a good point you made about it not being in affect above 62 because it happens any speed after around 65mph. So we can rule that out.
It really is quite a pain tbh all of this and didn't think that changing my tyres would be such a problem.

My tyre wear was slightly uneven with the outer edge wearing a little more quickly than the rest. But nothing to disconcerting.

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