Hercules Rockefeller

Like the title says, I want to know what will happen if I pull the ABS fuse in my car. Will it just disable the ABS system, or will it take out traction control and/or other active handling features?

sengli

Isn't active handling based on the ability to brake different wheels independantly? I would think by defeating the ABS it would take out the active handling. I know the bosch module for ABS/ handling went out in my Z recently due to a lightning strike at the house. And that module I beleive handled both functions.

BEZ06

Welllll......I'd say just go out to your car and pull the fuse and see what happens!!!

Butt.....I've done that for you. When you pull the ABS fuse you get lights illuminated in the IPC and the following messages in your DIC:

• Service ABS
  
• Service Traction System
  
• Service Active Handling
  
• Service Vehicle Soon

And the AH/TC button on the console doesn't do anything.

So......yes, pulling the ABS fuse affects AH and TC.

Bob

Bill Dearborn

All of those features are controlled by the EBCM. When you pull that fuse you cut power to the EBCM.

You also lose Dynamic Rear Proportioning which determines how much brake pressure should be applied to the rear wheels. Before 2001 the proportioning was handled by installing a spring controlled proportioning valve near the master cylinder. Since then the EBMC does the job.

Bill

Hercules Rockefeller

Thanks guys, just what I wanted to know. So if I want to run w/o ABS, I have to run with it all off. Last question: the car isn't going to go into "reduced power mode" or any other low performance mode when it detects a failure of the active handling system, correct?

Thanks again.

BEZ06

I don't think you'll have any problems.

When I attended Spring Mountain we did a number of wet skidpad exercises with the ABS fuse pulled. They weren't at speeds of more than 40 or 45 mph, but there weren't any messages to limit speed.

However......if you ever do those type of braking drills with and without ABS, you would NEVER want to drive without ABS and the control it gives you when braking hard and have to maneuver.

The ABS on our cars is VERY GOOD!!!! I won't drive without it on my car on the street or on the track.

Bob

Bill Dearborn

No. If you are doing hard braking you might get more rear wheel lockup since there won't be anything limiting rear wheel brake pressure. You will also lose Engine Drag Control and the Red Brake Light on the IP will be lit since Dynamic Rear Proportioning doesn't work.

Bill

Hercules Rockefeller

Well I have an adjustable brake bias valve in my setup, and I wanted to tune it in the absence of any electronic control systems to the point where the front tires would just barely lock up before the rears.

Additionally, while the ABS works very well at most tracks, there is a problem I frequently have with the system at Buttonwillow, in a corner called the buttonhook (I believe). It's basically a right hand hairpin with a braking zone that has a dip on the right side of the track. When braking hard through this dip, if you don't lift just the right amount at just the right time, your right front wheel will lose traction and trigger the whole damn ABS system, increasing your braking distance WAAY to much. I almost missed the corner last time I was there. I'd rather just temporarily lock/chirp the right front tire for a tenth of a second than have the ABS think I'm driving on icewater, increasing my braking distance by over 10 yards.

jvp

Uhhh... I don't doubt your track experience, but I question your explanation of it. The ABS in the Corvette monitors wheel slip independently and activates accordingly. Something else is at play here. Disabling the ABS in that section is going to be more than a quick lock-up: you're going to flat-spot your very expensive tires and potentially slide further than you already do. Remember: rolling friction is much higher than sliding friction.

My guess is that the ABS reaction is causing you to panic a bit and you then let off the brake pedal, which will lengthen the stopping distance.

I'd be really, really careful with this experiment.

jas

veech

Doesnt Pulling the Handbrake up just enough to trip the Light disable the Abs too? did on all my other Gm's

Bill Dearborn

Could be that or it could be he doesn't increase brake force when the wheel starts to ABS. When the ABS starts to modulate the wheel that means that wheel has lost traction and can't contribute as much stopping power as it could if it still had traction. You have to make up for that by increasing brake pressure at the other wheels.

If he pulls the fuse he will get the same thing except that wheel will lock up, pull the steering and provide less stopping power. A sliding wheel has less friction than a wheel that is close to lockup so the only way to make up for that is to press the brake harder to get the other three wheels to brake more. That is why threshold braking is difficult at times. Do you threshold brake just one wheel or do you let it slide and threshold brake the remaining wheels?

Bill

Hercules Rockefeller

Well this could be, but it sure doesn't feel that way. I could be mistaken about the "right side" only bit, the dip could extend to both wheels, but it's definitely a bigger dip on one side of the car. Anyway, my experience it that if I don't lift off the brakes just right at the dip, the wheels will want to lock, at which point the ABS kicks in, but the problem is that it stays on well after the dip has passed, I'd say for a good quarter of a second, when in fact the dip flies by in a few hundredths of a second. It doesn't sound like much, but it makes a big difference in braking distance. I know that a locked wheel gets much less traction than a static friction wheel, but if the wheel is only going to lock for a few hundredths of a second under low load, I'm not that worried about flat-spotting. What I am worried about is an over protective ABS system that drastically reduces the braking power to the wheels long after the low traction event has passed.

Really?!

hungryhorace

guys sorry for dragging up an old thread but I am having strange TCS issues.

Occasionally on start up I get the service abs, tcs, vehicle. Orange TCS light remains on the dash but abs turns out. I restart and it all resets, no codes pulled as none exist.

Pressing the TCS button does nothing, no lights, no comp mode. TCS is working but unable to affect a change by pressing the button. Checked the loom is connected on the switch,it is, the button illuminates when lights are on its just strange. Is there a fuse that controls whether the TCS button works?

Thanks and sorry for a thread ressurection

KLLRVET

How does your brake fluid look?

hungryhorace

Thanks for the reply, fluid looks ok. Is there anything obvious to look for? I heard about the steering wheel loom sometimes wearing, but would that not always present the error message on screen if unlplugged?

NoleenELT

How did you check the codes?

I'm guessing that the TCS codes won't show up on a normal ODBII scanner which scans for "check engine" codes.

Bill Dearborn

Steering sensor codes will generate Service Active Handling messages.

A bad wheel hub can generate Service ABS, Service TC and Service AH messages.

The TCS switch just provides a ground to a connector pin on the Body Control Module. The BCM then sends a signal across the GMLAN informing the Electronic Brake Control Module (EBCM) the switch has been depressed. The EBCM decides what to do from there.

If you have a problem with your tire pressure monitor system AH will be deactivated and you will get a service tpms system message.

ABS codes are only seen on ABS/OBDII scanners or fully capable scanners such as a Tech 2. An OBDII only scanner will not see any ABS codes.

A number of ABS codes are reset with each engine restart. Sometimes the only way to see them is to drive the car and once you get a service message or light have the codes read before turning off the engine.

Bill

hungryhorace

Cheers Bill

I know tcs is working though I will wait for a wet day and find an empty car park to test out the AH too, again no messages today - the easiest thing will be to get it into a garage but the problem is there are not really many places to go to in the UK plus I like to diagnose a fault first before a dealer decides to turn my **** into some form of piñata!

I only have a standard ODBII scanner, it didn't pull any codes which is good but also bad that it cannot see any ABS faults. My mate has a full tech 2 but other side of country, will be an excuse to go use his facilities!

I know you guys know this already but wow, what a car. Over here it gets so much positive attention and there is nothing more satisfying than American muscle humiliating European Prima donna's (such as the v12 vantage this morning (private runway etc)!

peterpiper

That would be very interesting! HR--you should be able to pull your E-brake one click and disable the ABS if this is correct. One click would be enuf to activate the switch but not activate the actual brake. (If not I can help you with a simple short of the switch)

hose the street down with water, and see if this works.... let us know your test results.

-pp

Yissa Olatunji

Does ABS wheel sensor work together with transmission speedometer?