Do not ignore VSC warning light at the track!

[ZDan]

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!

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!

[DarkPira7e]

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

[ZDan]

Originally Posted by DarkPira7e

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

It coulda been a *lot* worse...

[CSG Mike]

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.

[FR-S2GT86]

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.......?

[ZDan]

Originally Posted by CSG Mike

GLad you're okay!

Thanks!

Quick check: Is your alignment verified good?

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 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.

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.

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

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

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.

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.

[ZDan]

Originally Posted by FR-S2GT86

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.......?

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

[CSG Mike]

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.

[ZDan]

Originally Posted by CSG Mike

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.

[FR-S2GT86]

Originally Posted by ZDan

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

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.

[Breezio]

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.

[Jo0]

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 :/

[Turbo]

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.

[ZDan]

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?

Originally Posted by Turbo

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.