Took my car out in the snow today. Hit the brakes, all four wheels locked up, and the ABS didn't kick in. I slid about 30 feet with the wheels locked up before coming to a stop. I replaced an ABS sensor that I broke a few months ago. When I broke the ABS sensor, the ABS light on the dash came on. After I replaced the ABS sensor, the light went out. I don't know if the ABS worked then or if it has worked anytime since then as I never checked it until now. The ABS light isn't on on the dash. I read about the ABS system in the owner's manual and it says the ABS light should come on for 2 seconds when the ignition is switched on. My ABS light doesn't come on when I turn on the ignition. I ran an OBDII scanner and the only codes that come up are P1392, P0411, P0432, P0422. None of those have anything to do with the brakes. I checked all of my fuses and they're all good. Does it sound like the ABS control module is dead or is there something else I should check? I found someone on Ebay who rebuilds the control modules for a fraction of the price of a new one and for about as much as a used one.

 

Generally if the ABS module is dead the ABS and brake lights will come on, and stay on. Have those lights ever come on? If you pull the e-brake does the red brake light come on? It's possible the previous owner disabled them by removing the bulbs.

An OBDII scanner will only read the engine... You need VAG-COM to read the ABS and other modules. If you can't access the ABS module with VAG-COM then it's likely you will need to have it rebuilt.

 

Every cluster after '96 or so uses LEDs for warning lights so that's not the issue. Does ABS work under lighter braking? I'm asking because in my experience ABS stops working as soon as all 4 wheels lock up. If the light's not on then it should be working, I would still scan with a vagcom though, you're gonna need to buy one sooner or later anyway.

 

I suspected the ABS wasn't working prior to this so I had tried braking hard in a wet parking lot. I braked hard enough once that the tires squealed for a second. ABS never kicked on then either. Those are the only times I can think of where I would have thought the ABS would have come on. My ABS light has been on once a few months ago when I broke a sensor while replacing a wheel bearing. It hasn't been on since then. I just checked the emergency brake and the "brake" light doesn't come on when I pull the emergency brake. I don't know that it ever has though because this is probably only the second time I've ever used it since the car is an automatic.

 

Pulled up the rear seat and checked the plug for the ABS sensor I replaced. The sensor I bought didn't have the correct rubber grommets on it. So I pulled the wires out of the plastic plug on the new sensor to put the old grommets on the new sensor and apparently they got put back in opposite of where they should be. So now instead of brown wire going to brown and black to black, brown goes to black and black goes to brown. I unplugged the sensor and turned the car on. The ABS light didn't come on. I tried pulling the emergency brake and didn't get the "brake" light either. It seems as though something has fried. More than likely the ABS control module. Would that stop the "brake" light from coming on when I pull the emergency brake? I have a Haynes manual but the wiring schematics don't show the emergency brake switch anywhere.

 

The brake light should come on with with the e-brake regardless of the ABS module.

Do you have or have access to VAG-COM? Scanning for the module could give a clue to the issue (if it's not found then you'll need to have it rebuilt).

 

Pulled the instrument cluster out and all but 2 or 3 lights are LED. The brake and ABS lights in the instrument cluster are LED. I didn't see anything obviously wrong so I put the instrument cluster back in. After putting everything back together, suddenly the oil temperature gauge started working. It hadn't moved since I bought the car. And now there is also a green set of headlights that come on in the instrument cluster when I turn on the headlights. Once again, it had never worked prior to that. The ABS and brake lights still don't come on. I got a vag-com and scanned my car. Vag-com was able to communicate with every module except the ABS and air bag modules. That was disappointing because my air bag light was on from when I fixed my headlight switch and turned the car on with the air bag unplugged. Prior to getting the vag-com, it had been suggested that I unplug the ABS module and see if the ABS light came on in the instrument cluster. So I unplugged the ABS module and the light still didn't come on. I scanned the car again with the ABS unplugged and vag-com was able to communicate with the air bag module and clear its codes. I plugged the ABS module back in and vag-com was unable to communicate with the ABS and air bag modules. When I turn the car on, I get a few quiet beeps followed by three loud beeps. I thought the three loud beeps were because the air bag light was on but now my air bag light is off. The only light on is the check engine light. Are the three loud beeps because of the check engine light? Does it sound like the ABS module is dead? Vag-com doesn't show any faults when it scans the instruments.

 

The 3 loud beeps could very well be the CEL (check engine light) but when my ABS system was non-functioning the same 3 loud beeps made their presence known. I'm curious why your cluster isn't showing the ABS module fault, considering you can't access it.

 

I decided to troubleshoot the instrument cluster lights and see if I could find anything. I used this thread to find which wires in the plugs I needed to test and used a multimeter to check if they were getting voltage. The ABS wire was showing about 8 volts and the emergency brake (or parking brake) wire wasn't showing any voltage. So now I knew the problem must be in the instrument cluster. I took it apart to get a look at the LEDs and found my problem. It looks like one of the previous owners took a drill bit, or something similar, to the LEDs and broke them. I would assume either they got tired of seeing the lights on or they were trying to hide it when they sold the car. I had thought the ABS light came on when I broke the ABS sensor, but I guess it hadn't. So I used a multimeter to read the voltage the LEDs were getting. The ABS LED was reading 4.8 volts and the emergency brake LED was reading 11.8 volts. So I replaced the broken LEDs with a couple of 12 volt LEDs I had. Luckily there is enough distance between the circuit board and the gauge face that a regular LED will fit as long as you cut the legs down. So I didn't have to find a flat LED like the original ones. My ABS and emergency brake lights are now white instead of red and yellow but at least they work now. The ABS light is on solid and the emergency brake light is flashing. So my ABS module is dead.

 

Wow that's quite a shame, sucks to know people will go to the trouble of hiding an error instead of fixing it (especially when the fix can be as little as $50). At least now you have some resolution and can proceed forward.