ABS and ASC light

[ks20190]

Hi guys, I need some help here. On the way home today got stuck in traffic for about 30 mins on and off moving slowly, afterward going about 75mph on the highway, after i hit 70mph, the ABS and ASC lights both came on at the same time. When I got home I check all the fuse and relay, even try to disconnet the battery, but nothing change. The ABS and ASC lights is still on. HELP PLEASE!!! ohh my car is 98ti with auto trans. with 93k miles. Just got my front brakes replace two months ago and the rear brakes replace three months ago.

[Tyler]

Well when those lights both came on for me once and it was the Abs sensor that went,when that goes your ASC+T doesn't work. But my guess would be that.

[atlanta318ti]

I've got the same problem now. Just came on tonight as soon as I started the car. Both AST and ABS are on. 1997 Sport 125k.

For the last couple of weeks, I've noticed that it sounds like I may have a tire out of balance or the first hint of a bad wheel bearing. I can't yet feel it in the handling, but when rolling at 15-20 mph w/radio off, etc... you can hear that wo-wo, wo-wo, wo-wo (for lack of a better description). The last owner put the brakes on, but I don't know if they replaced the OEM rotors w/some cheap non-balanced rotors and that's what I'm hearing or even if it's a sympton of a worn out strut.

Anyway, on the ABS/AST fault light, Bentley suggests to check all the sensors first, but I'm wondering if that out of balance tire or wheel bearing may already have damaged the "teeth" on the "toothed wheel on the wheel hub" even though its not yet very noticable. I've not pulled the sensor yet, so I have no idea what to look for and I don't want to blindly replace all four at $100 each. Has anyone done this?

I normally DIY on this stuff. However, since I'm fearful that one problem may have caused another, I'm thinking about taking it to my local BMW shop (not dealer) rather than end up replacing something that may be fine and missing the actual problem. Plus these darn sensors are $100 a piece, and if I do have a front wheel bearing problem those are supposed to be a real PITA. Any thoughts on you guys that have a heck of a lot more experience than me?

[cali-ti]

as a first attempt, i'd pull out the ABS sensors and just take a look at them, cleaning them up while you're in there. a couple small bolts and they pull right out. you can at least check the condition of those that way. make sure the connections are all good as well. i can't imagine the teeth on the ABS rings would have gotten damaged. if you had the ABS tool, you could likely read the codes that are stored too bad we don't have that tool in-house yet (and i think you'd be third on the waiting list or so too). the sensors are easy to replace if they find that one of them is indeed bad. i'd order from one of the dealers that gives 20% off list (like crevier bmw in CA).

[atlanta318ti]

Thanks for the suggestion. I'll try that out first. In the least, it might help me narrow down which sensor could be faulty and save me some $$.

[thekinwc]

Mine came on and I found I had no brake lights as well. I found it to be the brake light switch causing the brake light failure. My abs light doesn't come on anymore. Don't know how connected that is but the wiring diagram shows the brake light switch running into the ABS module.