A few weeks ago I noticed that when I braked only at certain spots at low speeds right outside my garage (whether leaving or returning) it felt like the ABS was engaging for a few seconds...I ignored it until this week while driving to work, all three ABS lights came on the dash. After work I started the car and the lights were off and didn't come on. Every day for the next few days, the ABS dash lights would come on at the same spot on the highway on the way to work, but never on the way home.

We had an inch of snow yesterday in Minneapolis and on my way home (the dash lights weren't on) I braked when coming to a stoplight and the ABS definitely engaged. I almost slid through the intersection even though it really wasn't that slippery out. No dash lights came on.

This morning I started the car and now the ABS seems to be engaging every time I apply the brake, regardless of speed. I parked her and took the other car to work. My Peake tool is showing the code OF 79 Wheel sensor failure. I've been researching this and have come to the conclusion that it is either an ABS sensor and/or the ABS control unit (hopefully not the latter). I have no issues with the speedometer, transmission, or cruise control.

How can I find out which sensor it is? I can't diagnose which sensor it may be since I'm not having any problems with the speedo, etc. Do I just order one and try replacing each until the problem goes away? I've also heard they are easy to damage when installing. Mine is a 1999 and I've heard that was a bad year for the ABS unit, but if I can fix the problem just by replacing the sensor, obviously that is preferable. Does it make sense to go to an independent and have them tell me which sensor is the bad one?

Thanks in advance!!!

Adrian in Minneapolis
1999 540iA Sport (4/99)
Black/black
Clear sides/tails w/ homemade Stealth bulbs
V1 Hardwired
M5 grilles
Ecsta ASX on Style 32s
VW MAF
118k miles

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