Passat (B6) :: Parking Brake Fault Light Came On, Car Went Into Limp Home

Today the roads were slushy. On my drive to work a strange parking brake fault happened twice. Each time I was driving at highway speeds, not engaging the parking brake. In each case, the parking brake fault light came on, and the car seemed to go into some kind of "limp home" mode: the car would not accelerate or upshift, although it appeared to be willing to maintain around 40mph or very mildly accelerate from 0-20 mph if I stopped all the way. This was not because the parking brake engaged itself and was slowing the car - the car still coasted freely. It was clearly because the computer was limiting the car's power/speed severely. In the first case, I think it came on when I was beginning to apply the regular brakes to slow down gradually for a light; and in the second I was not using the brakes at all but did hit a puddle of slush. In both cases, it's possible the traction control kicked in, although I did not see that indicator light flash. The ABS did not get used based on sound and pedal feel in the first place, and because I wasn't engaging the brakes at all in the second case.

In each case, I was able to pull off the road, shut off the engine/car entirely, and then restart the car to clear the fault and turn off the light. The car drove totally normally from there, as if nothing had ever been wrong. There was around two hours including 90 minutes of being parked in my garage between the two events. I've never had any parking brake malfunction of any kind before with this car. So now I'm wondering when this will happen again. This does not appear to be the common problem of the parking brake button, since it never involved actually applying or releasing the parking brake and never involved me touching the button. I don't like having to quickly go from the left lane of a freeway all the way to the right lane or shoulder when my car suddenly decides to slow down for no obvious reason.