Do not ignore VSC warning light at the track!
 

VSC warning light is a negative image of the "VSC off" light, see below for pic. When it comes on (at least in my case), the "VSC off" and "TRAC OFF" lights will go out. I also got the "ABS" light at the same time, though I didn't notice it at first.

If you get this light (esp. accompanied by ABS light), you might have issues with ABS going insane and randomly locking front tires in the next braking zone! Caused me to boop the snoot of my BRZ at Watkins Glen last week.

I already made a thread on this:
https://www.ft86club.com/forums/showthread.php?t=142379
Just want to make sure all trackhounds are aware.

I was running at the Glen with the "5-second hold" on the TRAC OFF button, as per usual. Couple/three laps in I noticed the front left seemed to be a bit "overworked" in braking for Turn 1, kinda weird. Then the VSC warning light came on, noticed on the back straight. Entered bus stop chicane kind of tentatively, rounded turn 5 and braked early at about 85% for turn 6 (from well over 100mph) and front left instantly locked HARD, pulling car to the right. Tried modulating but got repeated front lockups even with relatively low effort at the pedal. Ran out of braking zone and got pulled off to track right by asymmetrical front braking, banged front right corner on barrier (flat panel backed by tires).

After emergency surgery performed by friends at the track, car was amazingly (to me) made driveable again in short order! :D

Friend at track plugged his laptop in with diagnostic software and we found wheelspeed sensor and yaw sensor error codes.

Went back out and got the same light after a few laps, same front brake insanity after light but not a problem as I was being *super* easy in braking zones. Went back out with pedal dance, same thing, again after a couple of laps.

Plugging laptop back in we found just the yaw sensor error code.

Ultimately I pulled the bigger, 40A ABS fuse and the car acted fine sans ABS. Could get lockup of course, but predictable, modulatable, and recoverable at 9 to 10/10ths driving. Ultimately went faster in the TT than I expected, 2:14.002, yay!

Anyway, word to the wise, if you get the warning light, take it super-easy next braking zone and pit-in! Diagnose if you can, but if you can't (error codes didn't show up with my code-reader btw), pull the damn ABS fuse if brakes are acting wonky!

Good information, glad you're safe. With those speeds, you're pretty lucky!

It coulda been a *lot* worse...

GLad you're okay!

Yes, if you ever get a video, you can see a sequence of the lights on your dash changing.

Quick check: Is your alignment verified good? I've seen (really) bad alignments sometimes cause this condition. If soemthing was damaged or bending from riding berms, etc., it could cause a transient condition where the alignment may have gone bad over time.


Interesting it's the front left, as every time I run into this condition, it has always been the front left. Under "street" braking, it will overtly intervene via VSC, whereas anything more than light street braking (even medium street braking), will cause it to go into failsafe with ABS and slip light permanently on. In this condition, once the ABS light is on, front left lockup was very easy.

Pre-maturely turning off all electronics, in my street experience with this, seems to prevent it altogether.


For posterity, when safe to do so, can you try pedal dancing, and see if you ALSO get this error? In theory the pedal dance mode should use the wheel speed sensors for ABS, but not the yaw sensor for VSC.

So I would like to add that your advice should probably be heeded even if you're driving on the street.

So the question I would ask you is if your suspension, brakes and tires sizes are stock or.......?

Thanks! :thumbsup:

Shop gave me somewhat wonky alignment: -3.3/-4.0 L/R front camber, zero front toe, -2.7/-2.8 rear camber, 0.05deg rear toe-OUT. Not a problem though. Car was handling fine before the light came on, save for perceived biasing of left front under hard braking. With ABS fuse pulled, was fine again, before and after adjusting the right front camber plate to balance front camber.

Interesting...

I had to do a couple/few laps at ~8/10ths before light would come back on, after which, front brake mayhem...

I haven't tried to induce the problem on the street, I might though. The good news (I think) is that before the light comes on, braking is at least "OK". Trouble only *after* light comes on. If I ever see the light on the street I'll pull the fuse immediately.

I left the fuse out for first leg of trip home, but found that eliminates cruise control so I plugged it back in!


Tried it with pedal dance at the track, again I got the light after a couple of laps. At that point I was taking it super-easy in braking zones though, don't remember if that stint resulted in front lockup or not.

Car is *mostly* stock.
245/40-17 Conti ECS street/rain tires (tires I was on when shite went down)
225/40-17 Hoosier A7 time trial tires
Swift Spec-R springs
Bilstein B8 struts/shocks
Raceseng camber plates
Whiteline rear subframe stiffeners (only change from last event at Palmer)
CSG Spec C2 front pads, Winmax W5 rear pads
5-lb. Shorai battery (-24 lb)
Girodisc front rotors (-12 lb)
removed rear seatback and tools from trunk (-25 lb, ish)
Weight for classification 2840 lb. with driver and fuel, roughly stock F/R distribution

I've not seen this really happen on 17+ cars without some sort of mechanical failure.

Outside of cleaning/checking all 4 wheel speed sensors, I don't really know where to point you, but am very much interested in seeing the outcome.

I'd be curious to see if the Yaw sensor replacement is the silver bullet in this instance.

I initially suspected mechanical issue. Inspected pads/calipers, removed shims (not that I thought they would cause problems but..), everything seemed fine mechanically. Running with ABS fuse pulled 100% fixed it.

I had a similar thing that was at least initiated by a mechanical issue at Mont Tremblant in '18. I got MASSIVE front *right* lockup going into the double-apex right hander at far end of track. I thought I'd had a blowout. Flatspotted the bejeezus out of the right front. Mechanical inspection showed that I'd installed one of the clips for the caliper pins backwards, I think the bent-over portion dropped down at brake initiation and got stuck behind the pad! Flipped the clip and problem solved that time.

This time, though, I gotta think it is indeed a bad yaw sensor. Something anyway that is telling the left front to brake WAY harder than commanded.

Understood. Reason why I asked is that obviously the more aftermarket mods that are made to any vehicle, the more chances you have to introduce new problems that wouldn’t normally occur otherwise. But we all know the risks we take when we make those modifications.

I also would like to know the eventual failure or fault that occurred to cause your issue when you finally figure it out. Not that I plan on making any suspension modifications as I don’t plan on tracking my car and I think it looks just fine stock, but it would be nice to know if this would be a possible issue on an unmodified suspension and brake setup.

Keep us informed and glad you’re okay.

I had those same two lights turn on while in grid (or at least that's where I noticed them) after a couple laps of AutoX about a month ago. It was a higher speed course with some road course sections. Turned the car off and back on, lights went away. Glad I didn't try running a lap with them on.
Car hasn't thrown that error since.

I actually got a yaw sensor error on the street/parking lot with the 5 second hold method. Wondering if I should hunt down potential faulty sensors and replace them after reading your two threads :/

Zdan - it's still worth verifying your alignment. I would also strongly recommend getting your car in the air and reefing on both back wheels to make sure you don't have any play back there.

I had the exact same set of lights/problems as you had. It happened to me a few months ago and the cause turned out to be excess rear toe caused by a suspension arm loosening up. I've also been told that a wheel bearing going bad can cause the same error & problems due to "play".

And -just to confirm my original diagnosis and fix- my stability light flashed on again momentarily at the end of a track session a week or two ago. Hit the pits, jacked the back end up and -sure enough- a toe arm mounting bolt had backed off enough to cause a bit of play.

Snugged it up, replaced the cotter pin and she's now good as new.

Alright, I'll do a suspension nut/bolt check and probably verify alignment before I go to NHMS.

Did you have massive front brake lockups?

Same
 

Glad to see this thread. Before a third track session of the day (in August 2020) had ABS & Traction control warning lights come on. The Torque app reported no error codes. Checked fuses, but didn't leave them out. Missed the session, trying to figure it out. Restarting the car was no use. Eventually, the lights went off on their own. And haven't returned after many following track days.



2014
stock brakes
CSG Tein Flex A's
tight suspension
-3 7/8° front camber, -3° rear, Front 1/16" total toe out, rear 1/16" total toe in

I had something similar happen at VIR this past weekend.
After hitting the gators coming out of oak tree the ABS light went on. No VSC warning light

The next lap, braking zone into T1, the right rear and right front locked up without much pedal pressure. Releasing the pedal did not immediately unlock the wheels. Flat spotted new RS-4s

ABS Light went off after turning off the car, and didnt have the problem again.




:iono:

Damn... So basically even if just the ABS light comes on, we should all be taking it SUPER EASY into the next braking zone! Damn haunted ABS/VSC....

I just pull the 40A fuse for tracking now. No matter what the computer *thinks*, it can't apply pressure to the brakes!
On the street, I haven't had any lights at all, and no weird braking behavior.

I wonder if there’s a correlation on brake fluid replacement intervals or if it’s solely an electronic issue.

edit: This only comes to mind because I know in some cars, brake fluid neglect causes premature failure or issues with ABS blocks.

It's not the brake fluid... For one thing mine gets fully flushed once a year, and for another in my case there is a yaw sensor error involved, which I don't believe could be related to "bad" or old brake fluid.

Yes - I nuked my set of AR1s because of a massive front lock up as the systems we're talking about failed (and turned off) in the middle of a heavy braking zone.

Did you check all your suspension arm bolts? Rear wheels for play? Alignment specs?


Curious what you found out because in my situation it was pretty cut and dried.

Did you do a 2:14 on the continentals or the a7s?

A7s, 5 seconds slower on Contis.

Just had the same thing happen on my FRS in the braking zone for T7 (hairpin) at Sebring. Lights out after restarting the car. I dont think I have my good code reader here unfortunately. DESTROYED 2 basically new GY Supercar 3R tires too :(

On the plus side I'm ~3 seconds a lap faster with CSG spec SRCs than the Eibach R2s.. @CSG Mike

Going to be a total ***** next time out... I still have tomorrow day, tomorrow night and sunday day track time this weekend so pulling the f'ing ABS fuse if I have to.

On a sidenote the car WAS just aligned. THe steering wheel is offcenter slightly so I'm wondering if it needs to be centered through the toyota software (techstream?). I checked all suspension bolts (always do after alignments) this morning and all were snug. I will check them again.

Wow, that is a HUGE difference. Impressive.

Well dang... At least you didn't hit nuthin!

Front lockups I presume? Symmetrically or did one side lock up sooner/harder? That was how it worked for me... Fortunately I was on Conti ECS at the time and they're hard enough they didn't get badly flatspotted.

I got the same behavior every time I went out, after maybe a lap or so the warning lights would come on and the fronts would be massively overclamped to lockup at the next braking zone.

I couldn't track the car safely until I pulled the fuse.

Next event at Palmer, first time out I forgot to pull fuse, so took it easy for a few laps then came in and pulled it. Unfortunately it was cool to cold ambient temps at Palmer and I had a couple of normal, controllable front lockups but flatspotted the bejeezus out of one of my A7s, had to TT on the Contis :'(

I felt like my CSG spec C2 front pads worked a lot better cold than my WinMax W5 rears, hence too much initial front bias => early front lockups. Wasn't a problem running sans ABS at Watkins Glen.

Just did some cruising laps (back to eibach laptimes lol) and it happened under throttle turn17.. acceleration went flat for a second like a fuel cut, looked at the cluster and witnessed them both light up then power came back. Took it super easy the next lap and brought it in.

Its throwing a steering angle circuit code every time it happens (turns out i did have my reader). I threw that clockspring in it from a wrecked car so I'm thinking its just damaged and getting worse... or that combined with the off center alignment is just enough to piss off the vsc system.

As for the lockup, front left, then front right, then both with the left leading a little. Breath on the brakes after they do it and they insta lock so i gave up on the tires lives to save the car instead.

This sounds very similar to what I experienced. Insane asymmetric front lockups at brake pedal forces way below what should produce that even without ABS. Initial diagnosis with normal OBD-II reader diag was steering angle sensor but deep dive with laptop and diagnostic software showed "yaw sensor error".

Interesting. My code reader displays the yaw sensor output live and it seemed ok (although sebring people weren't happy with my testing i bet). Steering angle showed -25 degrees when straight so that helped with the code error pointing to a specific issue. Helped by the fact i threw this clockspring in after it failed on srs testing in another car. I'm going to watch it tomorrow and if its annoying I'm pulling the fuse. Right now im just treating it like a time trial and doing 4 laps then coming in and restarting and doing 4 more ha

Full disclosure the alignment is also a bit more aggressive which will make up some of that improvement. The biggest difference is how the SRCs are handling the rough ass sebring surface. These bounce, a lot, but they don't violently toss the car a foot sideways like the eibachs did. T17 here is a lot better with the SRCs. My corner speeds in t10 and t13 are also multiple mph faster but most of the corner speeds seem similar. The SRCs are pushing more even with more toe out up front. Trying to adjust with tire pressure for that.

End of the day though, they are faster.

Oh also im using them with teins edfc active pro setup that ive now spent a bit of time fine tuning..

Dave, do you pedal dance?

Tracbox to do so, but yes.

Yeah, sounds like clockspring... My steering angle was reading normally when we checked it in the garage. If you have same pads front/rear probably better off to just yank the fuse. Crazily asymmetrically locking front brakes bad!

I ask because I get where Mike was coming from. Unless I'm missing some key part of the system, this has nothing to do with the yaw gyro or steering wheel sensor. Do you or @Opie have any spare ABS units to swap in for testing?

I doubt it, we never need them so they go to the scrap yard. I need to fix pad bias now ha

Oh, because abs fuse?

Yeah.. not the fronts lock earlier because of the pad.. running ds1.11 up front and only ds2500 in the back.

If I was in town (instead of at MSR Houston with the Austin86 & Houston86 groups) I would use the techstream to recalibrate the steering angle sensor and see if that improved anything. Definitely sounds TCS related. My car was hyperactive on track at one point last year because mine hadn't been recalibrated.

Were you also in PD mode? (full vsc disable, test mode, whatever we're calling it)

Yep