ABS Failure: Unwanted Emergency Braking

Hi.

I'm having the following problem with my Polo 6N1, which has a GTI engine from the 6NF. The issue is with the ABS:

Information about the ABS part: 1J0 907 379 (replacement part 6NX 907 379, I think).
ABS ITTAE 20 Gl V00
Softcoding: 01901, Shop: WSC 01901

Specifically, the car locks up completely when braking hard, and the brake pedal goes all the way to the floor. Then the pedal comes back up, and I can continue driving.

VAGCOM shows no errors in the memory. During the ABS test, the same error occurs with the front left wheel, while all other wheels are okay.

I've now replaced the control unit and the pump, but I'm still having the same problem .

What is this supposed to be?

Chris.

Hi,

Quote:

Softcoding: 01901, Shop: WSC 01901

It's a bit strange that the encoding and the WSC are the same... without looking up what 01901 represents.

If I understand you correctly, at least one wheel is completely locked, and even when you release the brake, it continues to brake?
If that's the case, you should take a look at your brake calipers and see if someone did a sloppy job when replacing the brake pads.

Best regards, Rainer.

Yes, he's still braking... I understand your surprise, but no one would believe it because no one has ever heard of such a thing before.

Why should the pedal then go all the way down, and besides, the brake works perfectly fine when the ABS fuse is removed ?

In addition to that, the front brakes on the G60 have now been replaced with new pads and rotors, but the same problem persists.

Encoding and WSC were the same... yeah, it was different after the change, and it reported coding errors. I then re-encoded it to the old values, and the error disappeared, and it worked.

I don't know what to do .

Sequence of the diagnostic process:

ABS Hydraulic Pump (V64) => works without issues.

front left inlet valve: 0 volts
outlet valve: 0 volts
wheel: locked

front left inlet valve: VBatt: outlet valve: 0 volts: wheel: locked.

front left inlet valve: VBatt
outlet valve: VBatt
wheel: Free => The pedal simply goes down to the floor with strange noises.

front left inlet valve: Vat: outlet valve: 0 volts: wheel: Free.

front left inlet valve: 0 volts; outlet valve: 0 volts; wheel: locked => Pedal goes back up (with my foot still on it *g*)

The tests of the other three parts are working perfectly without any slippage of the pedal.

Information about ABS part: 1J0 907 379.
ABS ITTAE 20 Gl V00
Softcoding: 01901, Shop: WSC 01901

Are the hydraulic lines connected to the ABS valve block mechanically misconnected, meaning they are somehow reversed or swapped?

Best regards, Rainer.

Is that even possible? I thought it wasn't supposed to be possible to swap anything. And if something *was* swapped, wouldn't the error be on the right side?

To avoid any confusion, it would be helpful to know whether the problem appeared immediately after the engine was rebuilt, or later, in order to rule in or out a compatibility issue.

It only appeared later. The engine, with all its components, was previously in another car where it worked perfectly fine.

The problem appeared approximately one month after that.

chris

So, without any modifications being made?

"Yes, nothing has been changed since then. I registered the vehicle in May, and I think I experienced that terrifying full-stop braking for the first time around mid-June..."

What exactly are you installing...? I read that it's a G60 brake system. Does the HBZ (hydraulic brake booster) work with the ABS and brake system? Could there be compatibility issues regarding size? It would be strange if it worked before.

Okay, for the Polo, there's only the larger front brake disc and brake caliper combination with ABS, which is fine. And regarding the G60: I only had to replace the caliper bracket to fit the larger disc; the caliper itself is the same (Girling 54).

But that has nothing to do with the ABS problem.

"But I don't think anyone can help me with this. So far, everyone I've talked to has just shrugged their shoulders. I've been to two VW workshops, and they had no idea what the problem was, and they were even afraid of the issue, meaning they didn't want to deal with it!"

Chris.

Here are the codes, following my list, that apply to the control unit in question:

01901
Polo 1995, production started in 09/94.

05703
Polo 1995, production started 05/97.

Please check while driving whether the wheel speed values in measurement block 1 are arriving consistently and uniformly from all wheels – preferably using a data logging function, recording one wheel at a time, and then another, and whether the brake light switch is being recognized in measurement block 3.

Then, after starting the system, check if the values 1+2 and 3+4 in the main working parameter (MWB) 2 are equal (these values are stored during startup). The difference between 1+2 and 3+4 can be up to 6 km/h (1+2) and 2 km/h (3+4). Otherwise, there may be a problem with the speed sensor or the distance to the ABS ring is incorrect or too large.

vagtuning wrote:

Following the codes in my list, here are the ones relevant to the control unit in question: 01901 Polo 1995, production started in 09/94. 05703 Polo 1995, production started 05/97. Please check while driving whether the wheel speed values in measurement block 1 and 2 are consistent and uniform everywhere - preferably using a data logging session, first one sensor, then the other, and whether the brake light switch is recognized in measurement block 3.

Okay, so the 01901 is correct, then. What is the 05703 for? Because the new ZE (Zulassungsbescheinigung - registration certificate) came into effect in 05/97, and I have that one. ???

What does that have to do with the brake light switch?

The speed will be displayed in the same units throughout the ride!

I would be interested in seeing a log from MWB 1 during the time the error occurs!
Okay, start the application, run it, then trigger the error by performing certain actions, and then check the logs!

Is it always reproducible? In other words, is it reproducible at any time?

I had a similar issue where the control unit had a circuit board failure. When you pressed the pedal, it would pulse like an ABS system, but the brake was fully released, and the car didn't slow down at all.

Well, the control unit has been replaced .

The error is reproducible at any time!