Random question on the ABS fuse
 

If I pull this fuse, what gets disabled in addition to ABS? Do I lose VSC and EBD as well? I'd greatly appreciate feedback from people who have pulled theirs. Thanks.

Why are you trying to disable the ABS? For track duty or some other reason?

I have not done so, so I can't offer any insight - but I would assume that you would lose any kind of stability control that relies on the brakes.

Two words: ice mode. It's a safety issue if my brakes quit working and I'm pointed at something more substantial than a cone.

Is this an issue that you've experienced in the FR-S?

It's a known problem in 997 Porsches (usually with staggered, R compound tires and hitting the brakes with some side load in the car) and I've experienced it once in a Boss 302R as well - but never in the Scion. I'd be interested to hear about it if it's an issue.

Yes you lose everything. There are two ABS fuses, one is 25A and the other is 40A, so they power quite a bit of stuff. The car isn't really meant to be driven without the system, at least on dry pavement. I've autocrossed on a fairly bumpy lot recently and have not experienced ice mode at all. People who left foot brake however have experienced issues, but it's likely related to throttle+brake at the same time. Just disabling the EBD via the "pedal dance" trick to put the car in maintenance mode makes the car go into ice mode more often.

I do a lot of trail braking. I get it a lot less if I brake in a straight line, although I was in a straight line last weekend when I hit the brakes and DNF'd my run...

Speed of brake application seems to play a factor too, although again this weekend I was already deep into the brakes when it literally popped back on me and became rock hard. :(

Ice mode is not a random thing. It happens when some series of events happens that makes the car think you are on a low grip surface. And the brakes don't just go away, thought he forces are lessened to about .3g when it's happening.

FWIW, I know at least two of us that have no ice mode issues what so ever. I also know that many folks have issues with it in all kinds of cars, and I don't in the same cars (Mustang, Corvette, F-bodies).

So it's the nut behind the wheel, combined with the nut's particular car setup?

I spent the last 7 years surprising autocrossing and tracking a car with no ABS. I guess it wouldn't surprise me that there's braking habits that may not play well with a commodity ABS system, but come on - this car has "sport" in the name. It shouldn't freak out because I put sport tires on and drive it sporty.

The Boss 302 Laguna Seca I drove for the first two months of the year gave me zero issues with ABS, and neither has any other car I've ever driven (too many to list). Not convinced this is all on me. If someone has concrete driving suggestions to offer, I'm listening.

Hey Manfred-

I had issues with Kevin's car on the Z2's with hard pedal, as did Clint at the Bondo event. I can commiserate, but have no solution for you other than don't stab the pedal and turn-

Thanks Elliot. Stab and turn worked great on the Celica...

It's definitely a combination of system and technique. For instance Bill Cook and his previous drivers never experienced it but at Dixie Mike King drove his car and had it happen all the time. Do you guys left foot brake? That seems to make the problem worse but may just be an effect, I had a tendency to stab the brakes more when I LFB.

I have read somewhere the ABS logic may take into account how fast you are braking, it might treat a quick stab as panic braking and trigger the ABS.

You can search for "pedal dance" and try it. Using that mode to disable EBD helped the track guys with trail braking, but in general just made ice mode kick in more often in autocross.

Are you using the stock pads?

Physics dictates that you can't stop and turn at the same time, not without lessening the pedal pressure as the cornering force ramps up, which is really trailbraking. Braking hard while trying to turn is not trailbraking and no car will be happy about that because you are asking too much from the tires.

This car has limited droop, and I suspect that some folks are managing to be so hard on the brakes when turning that the inside rear locks, and that will ALWAYS give you ice mode because there isn't any other reason normally that would happen.

A Mustang is something I'm familiar with, and guess what.... plenty of folks complain about the same thing on those. Corvettes too. :) I have issue with none of them.

The Mustang has a lot of inside droop, and a solid axle... and a lot of weight on the nose that makes it less likely to tolerate being stuffed in a corner on the brakes hard enough to cause you issue with the rear. But still folks have it happen because they just flat overdrive the tires.

The car doesn't freak out if you drive it sporty. Mine doesn't. Andrew's doesn't. This is a driving thing I'm sorry to say.

This. ^^^

It's a no-no with or without ABS.

Yes, stock pads. Do upgraded pads cause a bigger problem?

I've tried the pedal dance with little relief but I'm leaning more and more to using it - I need more experimenting (I've had the car less than 2 months). The less the system second guesses my actions the better.

When it happened Sunday I was braking in a straight line. I was on the brakes hard for half a second, trying to threshold and not kick in ABS, and then suddenly it freaked out. There wasn't any change in my inputs to the car.

I don't think anyone who has ridden with me or watched my driving would say I push the tires too hard with my trail braking. I realize my driving may need to change to keep whatever random ECU parameters cause this to stay within a normal range but it's hard to get more basic than a straight line braking maneuver. Do I need to worry about going over the side of a canyon? :iono:

I don't left foot... and I have never experienced the "Ice Mode" in my car... But Mike found it right away... it has something to do with the EBD on the car. If you brake and try to use the throttle at the same time, its seems to enhance 'ice mode' more prominently... The Brake logic that is implemented in this car along with the Traction control system doesn't like to have both the gas and brake pushed at the same time... and As Sam said, its very driver dependent. My normal co-driver hasn't experienced it either..and we have about 150 plus runs on the car..

Bill

I have a theory: what happened to me a week ago may have combined the panic brake feature along with ice mode.

When you trip the panic brake, the car decides the brake pressure for you - modulating doesn't have any effect. Then the other nannies (EBD, likely VSC, ABS) work at a layer underneath that - in other words, they aren't aware of whether the human is controlling the brake or the computer is controlling the brake, they simply respond to the conditions their sensors report. (As an embedded software engineer, this is more or less how I would implement the system. They're probably using an ABS controller from an older model without a panic brake feature and trying to integrate all the systems seamlessly for this one model is too much time/money.)

So if you're in panic brake mode and the ABS then trips ice mode, how do you handle this? Well, you are (apparently) in very real danger of hitting something and (apparently) there's not enough grip to stop the car. My thinking is that the system locks the brake pedal - if you're on ice trying to not hit something and you lock your wheels, you start running out of options very fast.

What happened to me was a LOCKED brake pedal and zero deceleration beyond engine braking. I can go out to my car, empty the reserve vacuum from the booster until the pedal is firm, but it will still have some give. Last week I tried to power through it and the pedal literally wouldn't budge. I'm not lacking for leg strength either.

I can live with "normal" ice mode. I can't live with this. The pedal dance disables panic brake so I'll be doing that from now on and we'll see if it happens again.

Any results on this? We've been getting the locked brake pedal even with the pedal dance. Going to try just pulling the ABS fuse this weekend to put the car into "No ABS Miata" mode - something I'm a little more comfortable with. :burnrubber:

I have only done 2 track days this year but I have pulled the green fuse both times and have not had any problems .

By the "green Fuse" you mean the fuse for the abs? So you did this with out any problems? Did the abs light come on? Did the car try to retreat to limp mode?

Im asking this cause im having issues with an ABS sensor and the abs light is on which in-turn activates limp mode. Do u think if i just pull the fuse the ecu will forget abt the broken sensor and if i clear the fault codes my car will get out of limp mode??

I need a solution cause my local toyota and Subaru dealer both need over a month to get the new sensor.? and im stuck in limp mode now :(

I ran the whole track day like that although a bunch of lights came on in the cluster but the car drove normal with no limp mode

I've had my green fuse out for a month now.. I don't believe I have experienced any limp mode. My ABS is off and my traction control and VSC is disabled.

(And for some reason my e-brake light is always on.)

Pulling the ABS fuse or adding a "blown" fuse is not legal for stock or the new street class. I minimize ice mode by changing my line into a corner requiring hard braking by entering wider and braking more in a straight line to limit rear wheel lift, which can increase the chance of ice mode. I have also read someone had less ice mode with more aggressive front pads vs rear pads to get more braking on the front wheels. Trail braking and ABS are not a good combo...

^^This^^

Had a tC that would lift a rear wheel trail braking which would put it in to "ice mode". I was able to dial out most of it by putting aggressive pads up front and leaving the stock pads on the rear.

And your car was able to brake better even with the heavier front brake bias? What brand pads do you use up front> I was looking to get Carbotech AX6 pads

Yep, the braking capabilities were significantly improved. I was running dot r-comp tires at the time so the fronts had plenty of grip. The ability to trail brake became a lot more consistent and I could also get on the brakes harder and later.

I used the Hawk HP+ on the front. For autox I bet just about any pad that works well at low to medium temps and has good initial bite would be fine.

Which fuse is the one to pull the 40A or the 25A one?

and the e-brake light on the time means the active 'diff' is on where the brakes are applied to the spinning wheel to try and give some LSD action

Bringing this back up to the top. Does anybody have more input? I pulled my 25A fuse for the abs today and got full christmas tree mode on the instrument cluster...