ABS Module Replacement?

[bisonbrew]

What questions should I ask the mechanic to troubleshoot before continuing repair process? ABS warning had come on the day before a road trip home, but gone off again within a couple miles, so next morning I just got on the freeway to go home since no brake problems were apparent. Couple stops at rest stops and one fuel up--no brake problems. Coming off the 800 mile road trip, I pulled off fwy to pee and get fuel 20 miles from home. As I came to stop on offramp, and the brakes felt "grabby" and the ABS warning light comes on again. After fueling up, restarted car, ABS light still on, but now brakes had become spongy. Drove to a nearby brake repair shop instead of my usual VW repair shop. They said my rear calipers drivers side pad was gone, and recommended a master cylinder replacement, replace calipers, pads, and flush system. I approved it, as it made sense at the time. They did it and said still spongy. For no additional charges, they have replaced master cylinder twice (new parts), flushed multiple times as they troubleshot, and recently they replaced the booster with a new one...still didn't fix it. They said they would take out the new booster and return it, put on my old booster.....They isolated each brake line to check function and determined that the right front brake output from the ABS module was not working. They now suggest they buy a used ABS module from either a gas or diesel model, and they would install it for me for just the cost of the ABS module and a couple hours labor. Should I proceed, or ask specific questions first??

 

[BobnOH]

Find out if it was properly bled using VCDS (or equal). You might ask to see the device or, a more innocent question, How much fluid did you use when you bled it? I believe it takes near 2 big bottles are about 2L.
It may be all cars now, if the fluid runs below the cylinder (or you replace) the ABS bleed must be done.

 

[oilhammer]

So, before this Fail Train of throwing parts at something left the station, did anyone possibly ASK the ABS module what was ailing it??? OBD works, always start there.

Here is what should have occurred:

ABS warning lamp comes on ---> suitable scan tool attached to DLC and ABS module DTCs recorded. That is Step 1. Somehow, this shop skipped right past that, and is stuck on Step 23, and clearly screwed up a bunch of stuff.

ABS and the service brakes, while they work in conjunction with one another, are two different entities. Your linings can be neglected to the point they go metal to metal.... but the ABS has no idea, and really couldn't care less. The only way the service brakes could cause an ABS problem is if there was some strange loss of pressure or a wheel was locking up, or the brake fluid went too low in the reservoir.

 

[Couleetdi]

Possible solution

I see you have a2003 Jetta. I do too.

There is an undocumented FSB on bad ABS modules, dealer replaced mine for free, charged me for brake bleeding though, which peed me off.

Symptoms were same as mine, later the brakes finally locked up tight, about threw me thru window doing 55 mpg.

Check with local dealer first.

coulee

 

[bisonbrew]

Thanks for replies. I'll follow through and report back.Forgot to say that at the fuel station I checked master cylinder reservoir and it was full. Then went in to shop. They speculated that the uneven rear brake pad wear meant the rear caliper drivers side was sticking so change both. Agree a VagCom should have been step one. I'll see if they did that. Again. Thanks for the leads.

 

[turbocharged798]

There should be no need to speculate if a brake caliper is sticking. If a wheel is hot after a drive you found your problem....

This shop is just firing the parts cannon at your car to fix the problem.

 

[Genesis]

... and billing you for it.