ABS Locked my car up in the middle of nowhere...

[ditchbum]

Where else would you want to break down? Anyway, ABS suddenly activated for some reason. Dry road, curvy mountain pass, going uphill. My car, a B-5 wagon, has had a porsche brake upgrade in the front and when I changed the pads noticed some sensor wires taped up and tucked out of the way. I thought those would be for th ABS system but not sure. The brakes continued the depress until the vehicle STOPPED moving, Fortunately I was able the get into a roadside pull-off just before full stop. Let it rest a couple minutes, tried to restart, ABS still ON, Brakes still locked up. Having it towed home which is not terribly far ( 30 miles ). Any ideas on what gives? Or in my case, what doesn't give?

 

[gearheadgrrrl]

ABS failure would more likely release the brakes.

 

[ditchbum]

So, what causes ABS to engage? Out of the blue? Bad wheel sensor? Bad pressure sensor? Any help greatly appreciated....

 

[PickleRick]

Did all brakes lock up? I always found abs failure to result in.... being able to stand in the brake pedal and be able to make the brakes lock up as the abs keeps you from doing so. The abs does the exact opposite of applying max pedal pressure to the wheels as far as I understand it.

I have seen far more brake calipers and wheel bearings cause a wheel to lock up. Seen plenty of decorating rubber brake lines cause the caliper to drag.

 

[ZippyNH]

Abs units tend to fail so you CAN lock up a wheel with the light on, defaulting to old school regular brakes.
Brakes that lock up and stay locked are usually a brake line issue, sometimes internal to the rubber lines ASSUMING the rest of the system has been well maintained and has the correct fluid
Then again...."upgrades" with spare wires floating around....good luck with that.

 

[turbodieseldyke]

Unattached wires near the front brake calipers are usually pad-wear sensor wires, either because their new pads don't have plugs for the wires, or the system is falsely signalling "low pads", so the user removes the wire to remove the idiot light from the dash.

 

[ditchbum]

So, as I want to describe the problem correctly, I was driving UP a mountain pass, very curvy, when I notice a loss of power coming out of a hairpin curve. Happens just as I crest the pass. I upshift 1 gear ( to 3rd ) and definately notice a loss of power going downhill. That's when I notice the ABS light ( also esp? light ) Give it some throttle, like trying to push a rock uphill... finally find a pulloff, brakes are smoking, left front for sure, so I stopped. Let it rest for a minute or two, tried re-start, light still on. Tried moving the car in 1st gear, nothing. Reverse, nothing, dead stop. My guess, all four wheels were locked. Hitch ride home, call tow company, wife gives me a ride back to the car, about 2 hrs later, car starts without light and moves freely. Tow home anyway, $250 lighter.... Thoughts anyone? Thanks, turboDD for the tip on the pad sensors, THAT'S what those wires are....

 

[turbodieseldyke]

The abs/esp lights might just be the computer saying "hey, we're seeing weird inputs". Could be your caliper is just frozen shut. You'll have to jack it up & spin the wheels to see what's wrong.

 

[gearheadgrrrl]

ESP can activate the brakes to stop wheelspin, but only on the drive wheels of which you should have only two.

 

[JoeTDI65]

I had a situation before on an audi similar. Brakes kept getting stiffer and stiffer, then locked. It ended up being a vacuum line coming of the brake booster. Not sure if that helps. But your posting made me think of if.

 

[ditchbum]

a quick update... took the car on a quick spin, felt like driving through wet concrete. Very sluggish acceleration. Turned around, went home . Felt brake discs and all 4 felt very warm. My initial take is that all 4 brakes are not fully releasing but I've not a clue why this would happen. ABS failure? Would think the brakes wouldn't lock like this car did....would just act like no ABS correct? Brake pressure sensor bad? Can it be tested? Will check any hoses associated today but any other thoughts are appreciated....

 

[turbodieseldyke]

Have you scanned for codes yet? Not OBD, but a Vag scanner.

 

[ditchbum]

Just ran a scan and came up with a boost pressure regulation P0299-000 which is interesting, and the ABS Brakes came up red though it said no DTC's found, Not recognized or communication error. Just blew an intercooler hose on a midwest trip, one that I had just replaced as a preventative, put in another new one, still looks good now, hmmm. That's pretty much it, besides a communication error with the radio, as it has been replaced. Have not checked the hose on the bottom passenger side... would bad wheel sensor(s) cause bad/ no communication as per vcds?

 

[P2B]

the ABS Brakes came up red though it said no DTC's found, Not recognized or communication error.

Do you mean VCDS is unable to connect to the ABS controller?

would bad wheel sensor(s) cause bad/ no communication as per vcds?

No

 

[ditchbum]

Just ran a scan...that's what came up. Is there another way to communicate with the ABS controller via vcds?

 

[P2B]

Just ran a scan...that's what came up. Is there another way to communicate with the ABS controller via vcds?

Click Select then ABS Brakes to open the ABS controller.

You might find this VCDS simulator helpful:

Ross-Tech: VCDS Tour - Main Screen

 

[ditchbum]

So, I did a new scan of the ABS controller and had no fault codes. Did not run any measures or whatever you can do. What I did find was the vacuum hose coming from the turbo actuator melted (shut) , hence the lack of power I'm guessing... question is, would this condition somehow affect the brake system enough to throw an ABS/ESp light?

 

[P2B]

A vacuum leak will affect brake power assist. I wouldn't expect it to affect ABS, but maybe...

 

[MEgearhead]

Crack the bleeders open at the calipers. If brake fluid comes out under pressure, it's a hydraulic brake problem. If not, it's probably mechanical (stuck caliper, or e-brake on the rear.). If you have Brembo 17 or 18z (Porsche Cayenne) calipers on the front, you can probably get to the outboard bleeders through the wheels.

 

[ditchbum]

a quick update, fixed vacuum leak ( line melted at the turbo actuator...) power restored. Abs system has quieted but not sure if it has been fixed, will try the brake fix next weekend....

 

[ditchbum]

so, the brakes on this car are puzzling me..... car runs and drives fine. Took for a spin up the same mountain pass where I got stuck, and the brakes locked up AGAIN. This time, No lights....(Abs/Esp...) and when I say locked up I mean the car slows down on it's own until you can't move. Shut the car off for a few seconds, start up, no lights (still) , drive back home without incident. I am stumped by this behavior. What would/could cause the car to think it needs to stop on it's own? Bad ABS unit? Wheel sensor? What does the Brake pressure sensor do? Anyone have one of these go bad? Need help/ advise ....

 

[MEgearhead]

Are you sure it's the brakes? It doesn't sound like it to me. What have you done to verify it's the brakes?

 

[ditchbum]

When it happens, the car still runs fine. It just won't move. Put it in gear, stomp on the accelerator, nada... reverse, nada...it feels like trying to move the car while the the emergency brake is on. turn car off for a few seconds, it 're-sets ? and drives normal. What else would it be besides the brakes cause it sure feels like the brakes engage until the car stops. The re-setting part is the puzzling part for me. Sounds like some sort of electrical signalling issue telling the Abs/Esp system to shut down for some reason. There's quite a few choices there, but am hesitant to just start replacing wheel sensors and /or brake pressure sensor as it would be nice to test? them. Is this possible? Thanks for the help....

 

[MEgearhead]

There's no point in replacing any parts just yet, because you don't have anything definitive. Take baby steps starting with the very basics. When it "locks up", if you shift into neutral will the car roll?

 

[ditchbum]

No, definetly no

 

[ditchbum]

Yes ,I misspelled definitely, sorry that one gives me trouble

 

[MEgearhead]

No problem. Does it happen if you turn traction control off?

 

[ditchbum]

traction control? How do you turn it on? Did not know that was a feature of this car. Sorry if that sounds ignorant but I guess I am concerning this manner. I'll go look in the owner's manual...

 

[ditchbum]

So, it turns out this car ( a 2004 ) has an ESP button. would this be considered 'traction control' ? If yes, then no I have not run the car with the button pushed. It does sound like it works with the braking system. Are there components involved with that system that go bad?

 

[MEgearhead]

So, it turns out this car ( a 2004 ) has an ESP button.would this be considered 'traction control' ?

Yes that's it. Electronic Stability Program or something like that.

It's on by default, you use the button to turn it off.

Are there components involved with that system that go bad?

Not normally. Have you done anything with the axles or outer C/Vs recently?