HiFlite999

iTrader: (2)

Up to a couple months ago, the ABS/SAS/TC seemed to work just fine. Lately however, in hard cornering, it just shuts off (all the related warning lights come on), and I don't feel any of the nudges from the intervention I felt before. In particular, running hard up freeway on-ramps will always trip the system off if there are any bumps at all. Very odd especially since there have been no changes to the car (tires, brakes, etc) that might have unbalanced the system somehow. Also, there's no rust and minimal undercarriage dirt since the car has not been driven in winter and only very seldom in rain.

Any ideas what's going on, or how to troubleshoot, or fix it?

yiksing

Nothings wrong with it, it is in fact praised to not intervene too early so drivers can have a little fun with it. It might have behave differently due to your change in driving style, you might have improved (the right thing to do) in pushing the car harder during cornering that the DSC regards it as within the safe zone (waiting for driver intervention) before it starts intervening or

the DSC did not feel the need to activate the brakes and only reduce engine output during those particular incident.

my worthless opinion...

Flashwing

You can fix it by turning it off. It just gets in the way.

Ryan2008

What he said. ^^

RIWWP

iTrader: (2)

...


Ignore the arguement on if you should or should not drive with it on for a minute.



HiFlite,

Is it actually intervening? Or are you just seeing dash lights come on?

If you are seeing dash lights come on, which ones are coming on, and when do they go off?

If you are only getting the swiggly tire lines in the center, and it was a valid trigger, then you should feel at least a slight shift in the car, since it applies brakes to 1 or more wheels, depending on what is needed at the time. If you are near the limit of grip and hit a bump, it is very easily triggered. IF triggered, usually it flashes 3 times and disappears.


However, if you don't feel any of this, or are getting more than 1 dash light, or it goes steady or keeps flashing for a while, then there is likely something the ECU is detecting as wrong.

This could be as simple as a sensor that is dirty as failing. However if there is actually something wrong with the ABS system (since that is what the DSC is based on), then you could have a serious problem on your hands. ABS failure is rare, but possible. And when the ABS fails, generally you won't know it until you need the brakes hard and need them NOW, and basically it will put all the braking force to a single caliper, locking that wheel up without any appreciable braking force being applied to the other rotors.

See this thread from Eric Meyer about his ABS failure during an event. Very fortunate he had a clear path through the cars. (https://www.rx8club.com/series-i-wheels-tires-brakes-suspension-55/here-what-happens-when-your-abs-fails-190041/)




Now, if you gentlemen wish to continue the old debate on whether or not to drive with the system on or not, feel free. But that isn't what he asked. The OP has proven intelligent enough from his time here that I doubt he is asking a simple "did ABS trigger?" question.

zoom44

yeah guys clearly he is saying that the system fails. this could be an ABS issue that need to be looked into.

have you changed your brakes or wheels lately? changed tires lately? NOT changed your tires in a long time? had the steering wheel off for any reason? changed any suspension settings in the front?

Ryan2008

At least I read what he said before posting.

Kidding Zoom but yes this could be a safety issue so I apologize for just brushing it off. I unfortunately do not know much about the system so I can't be of much help. Good luck with it though.


Ryan

shaunv74

I'm guessing your tires are getting old and hard and are slipping more easily. I noticed my DSC kicking in on me much more frequently all the sudden when my tires got to about 3.5 years or so old. They had heat cycled out and hardened up. They had much less grip. I replaced my tires and there was big drop in the amount of times I was firing off DSC.

zoom44

i read that too but the reason for my questions is not what you think. he wrote there werent any that might have unbalanced the car. I was asking if anything had been done at all so we maybe could focus on wheel speed sensors etc. work that might not unbalance the car and work that might have broken or left a sensor unconnected are two different subjects.

HiFlite999

iTrader: (2)

Thanks. Yes, I'm familiar with how it should act when it's working properly, I feel the intervention and the little squiggly lines light flashes, then goes out. What's happening now is zero intervention and all three lights come on (DSC, Wigglies, and ABS) and stay on until I shut off the ignition. Turning the switch back on lights them up normally, restarting the car makes them go out normally. I'm also not getting the wiggly-line light when chirping the tires during a hard 1st-2nd shift as before, but that as yet has not shut the system down entirely. Good point wrt the ABS; I'll up my priorities in getting this fixed. I'll try to find some sandy surface to try out the ABS specifically.

It amuses me in a fatalistic way when I hear the "real men" arguments against DSC, ABS, helmets for motorcyclists, and other safety features. I have heard the same stuff regarding seat belts, radial tires, airbags, and so on blah blah. Dead is stupid. So is paralyzed for life. I've seen both happen to "real men" friends of mine, who were self-declared above-average drivers ... until they weren't.

RIWWP

iTrader: (2)

This sounds like the system is detecting different rotational speeds (i.e. circumferences) for 1 or more tires.

I get this occasionally with my winter set, as they aren't quite the same circumference front and rear.

I get the same with the wheel spin as well. With the larger set in the rear (I'm talking like a 3% difference, not much), I can spin the rear wheels more than with my equal summer set before the TCS kicks in. I swap them around, TCS kicks incredibly easily.

Either orientation though, if I play around a bunch in the snow without disabling the system, I can easy send it into the same 'mode' you are getting into, where it can't figure out what is valid and what isn't. A product of slightly different circumferences front and rear.


If you have equal sizes on all 4, then you may have 1 or more wheel speed sensors failing, and sending false signals. When you are driving straight, the other sensors override the failing one, but when you are turning hard, each wheel is rotating at a different speed. Usually, the system detects this as a stability loss and intervenes, but not every "difference" is a valid stability loss, and this unknown area is where the system is seeing the situation, so it disables it as expecting a fault.



Definitely test the ABS if you can.





And I agree

DSC has saved my life and/or my 8 quite a few times. Only once was it for something other than my own stupidity (oil on the highway at ~55mph). Sure, if I wasn't stupid I wouldn't need it, but having it meant that those times of stupidity didn't cost me my car, my health, my life, or any of those of someone else. One of those things that you only need once to be entirely worth having.

bse50

How's your battery working? Had a similar problem with a dead battery
This may not be the case but it's an easy check!

Razz1

Sounds like he stores the car for winter.. so why has nobody asked about tire pressures?

If he's getting better and is not jerking the wheel and pedal as before, he won't get any warning signs. It should just go into limp mode.

1RadRotary

Mr. RIWWP you are sooo much help!! I'm having the same problem and now i know why. thanks a lot for unintentionally helping a brotha out lol

RIWWP

iTrader: (2)

I don't help on accident.

I get really freakin wordy without intending too, but I help intentionally.

Glad I could be of assistance.

Ryan2008

Good point, got me there.

HiFlite999

iTrader: (2)

Yes, tire circumference could be an issue. They are the basic RE-40's, but have differing amounts of wear. It's been this way all along though. I would have thought that one speed sensor failing would result in a "kick off" even going straight, but who knows what it's programmed to do in that case. I know in general TC and ABS can get very confused on ice, where for example it can't decide which wheels are slipping and which aren't. My particular problem though is that DSC used to work and now it doesn't under the same conditions.

One thing about ABS, TC, DSC is that it can't do things with car that it is not possible for the driver to do regardless of skill. Where the rules and team resources allow it, such systems are showing up on race cars. A properly done system will make the car faster, not slower, plus being much more forgiving of mistakes.

HiFlite999

iTrader: (2)

Good point, but checked them. I was running 35 psi very equal. I'll drop them down to the stock 32 psi and see if the problem is still there.

HiFlite999

iTrader: (2)

Battery new in March 2010 and voltage looks fine ...

HiFlite999

iTrader: (2)

Both front wheels have been off several times to change plugs, to remove the inner fender liners, and to access the air pump connection on the exhaust manifold. Did I disturb something? I don't think so, but maybe. Wouldn't a disconnected wheel sensor fail the startup diagnostic though?

Tire change, no, but they are old. It's an 06, but only 17k miles.

Brakes? nothing done to the brakes.

Wheels, not since last fall and DSC worked after.

However!!

Perhaps that wheel change got things close to an edge I'm now over for some reason or another, since as pointed out above, my hard corners are probably harder as I've gotten used to the car. The new wheels are 18"x8.5" with a +30mm offset which increases the track width by 30-35mm over stock. This may move the car dynamics close to an edge in the DSC map of what is normal. Humm ...

Consider just the ABS function to keep things simple. In a straight line, computer has an easy decision to make: when a wheel starts to lock up, the sensor shows a speed difference of that wheel relative to the other 3 and and the computer then eases up on that brake to allow the speed to match. However, in a corner, things get messed up, because in a normal turn, the outside wheels must speed faster than the inside (and the outside front goes faster than the outside rear, with inside front faster than inside rear). In order to compare wheel speed to find which one is wrong, the 'puter must decide what speeds are right considering it sees the steering sensor indicates a turn. But thanks to the increased track there's already an "abnormal" speed difference left/right that puts it closer to saying "locked wheel", but the speed difference front/rear on the same side is essentially unchanged by the increased track. If a wheels gets completely locked, then the computer gets a locked/locked signal and it knows what to do. However as it just starts to lock, it gets a "locked" from say the right-rear/left-rear compare (because of the speed difference caused by the increased track plus a little braking induced slip), but a "not locked" from the right-rear/right-front compare because that part of the map doesn't have a track induced error. The wheel can't be both locked and unlocked; the system goes , generates a fault condition, which then turns on the warning lights.

If a 3% Front / Rear circumference difference is enough to cause problems, is it possible that a 1-2% track increase could also do it? (But I haven't noticed anyone else running 'popped' wheels complain or comment on problems with DSC ...)

RIWWP

iTrader: (2)

Not quite. A driver can adjust front/rear bias or braking pressure, but not left/right, which a DSC system CAN.

Agreed. I haven't seen anyone else with a staggered wheel setup commenting on issue. I assume (and it's a pretty large and probably faulty assumption) that people with staggered setups get setups with circumferences as close to each other as possible. Then again, if any of these are on base models, then they wouldn't even notice as those 8s don't have DSC.

The one thing I do not know however, is if the differences in rotational speeds/distances that the system is comparing is percentage based or absolute values. I.E, is it looking for a difference of +/- 3% or +/- 1 revolution per minute (or whatever time segment)


Lets see what tire wear might do to rotation...

Going to use your wheel sizes here, making an assumption on the tire size of 245/35/18.

Thanks to http://www.miata.net/garage/tirecalc.html
A diameter of 24.76in and a circumference of 77.8in, resulting in 815 revolutions per mile. (24.8 x pie = 77.911 which doesn't round to 77.8, vs 77.8 / pie = 24.76, which rounds to 24.8 so adjusting the diameter to match)
Assuming that is calculated "as new", at 14/32th tread depth. (I think that is standard)

Wearing it down to 4/32, you now have a diameter of 24.635, a circumference of 77.36, which results in 819 revs per mile, or a 0.4% increase in the rev speed.

Given that this isn't even half a percent of change, I can't believe that tire wear alone could cause the system to get pushed over the edge. I also don't believe Mazda engineers / programmers would have not built in this possible variance.



So not tire wear.

zoom44

and leave you with nothing to do?

zoom44

im thinking it might be a brain issue. stll should give a look at the abs and wheel speed sensors in case something is not connected well or a connection has got dirty etc, i'm thinking along the lines of the power steering connector issues and the eshaft sensor fouling.

but it might need a look at from the dealers computer

HiFlite999

iTrader: (2)

Yeah, I'm leaning toward dealer computer. Thank y'all for the good ideas! Unfortunately, the city decided to start repaving the street in front of my house, so the batmobile will be trapped in the garage for the next few days. I'll post up what I find out, and hopefully the solution.

HiFlite999

iTrader: (2)

Well I finally got the car to the dealer for this problem (4 yr bumper-to-bumper warranty expires in 5 days). I only got to speak to the service writer who relayed to me that the mechanic's verdict was the difference in tire wear. It's unknown to me if he actually put it on the computer. (Though he did diagnose a bad sensor in the driver's side seatbelt mechanism which I presume implies a computer hookup.) I suppose I could test the conclusion with a purchase $900 worth of new tires, but that's gonna have to wait.