ABS light is on

What have I said that would make you think that?

Chris

So the statement should be "The ABS light being on means the ABS will

I was just trying to point out that a single indicator light can't be relied upon to show the status of a complex system.

Chris

Without regard to what Chris is saying, if the ABS light is on, then you should consider the ABS feature to be inactive and your car may skid in a situation that would otherwise trigger an ABS event.

The only way to isolate the cause is through the diagnostic port. You could buy some speed sensors and swap them around until you find a combination of new andn old that work, but this is a more costly and time-consuming approach than paying somebody to plug into the diagnostic port.

The diagnostic port will identify the controller module as the fault, if it is the source of the problem.

To all intents and purposes it does, in as much as turning the steering wheel will cause the steered wheels to move.

It does do a rather accurate job of it though. And the edge case is somewhat pointless to consider.

The truth is that your single data point is not an indicator that the complex system might work.

FOR THE RECORD I have an E36 with the ABS light on, and it's been on for well over 5 years that I know of. My car has a problem with the valve body and I don't care about it enough to fork over $1000. I've driven most of my life in cars that don't have ABS at all, so having a car with ABS that doesn't work is no big deal in the grand scheme of things.

Actually you can diagnose them with an oscilloscope or most decent digital multimeters. There's enough voltage output to drive the frequency meter on anything 1/2 decent.

Agree.

Disagree.

(The OP's car is pre-E-OBD, so may have limited diagnostics.)

Examining the sensor rings and sensors for physical damage, cleaning them, then unplugging the sensor connector, cleaning it, and reconnecting it will resolve 50% plus of ABS faults. The diagnostic cost as a DIYer will be zero.

The more competent DIYer should then be able to use a multi-meter to determine which sensor might be faulty simply by comparison of readings.

Compare that to what a BMW dealer (at least here in the UK) will charge for diagnostics...

No it won't.

In the case I mentioned in another post, the ABS module had a short circuit internally for the warning lamp output. This wasn't monitored by the diagnostics. (This wasn't a BMW, I should point out.)

Chris

Ah, I see.

You don't live in a country civilised enough to require your car to have regular examinations to make certain it meets the safety standards the manufacturer built it with.

;-)

Chris

Yep, even with a fairly basic DMM you can spot the most common fault of no output.

Chris

Yep, and usually 0.0vac on the faulty one!

Chris

I think that you'll find this is an MOT failure now..

There is a firm who do very good recon's of these units. Used them last year on our Volvo 850 very quick service. There are others around might be an idea to give them a call..

Translation: learn to brake properly and to feather the pedal. Practice some skids in a wet parking lot sometime and get a sense of what they feel like and learn not to panic.

Then whether or not your ABS works, or whether or not you happen to be driving a car equipped with ABS, then you will be safe. Or, as safe as you can be driving on public highways shared by crazy people, which really isn't all that safe actually.

--scott

But in that case the system doesn't "think" there's a fault. There's a fault that makes you "think" the system "thinks" there's a fault when it doesn't.

Where the system "thinks" there is a fault it will disable the ABS.

You can. I could probably figure it out, but the OP thought the CHECK button on his OBC held the key to his troubles. Clearly he's gonna need help with this or he wouldn't be here.

If he could figure it out AND had an o-scope or a DVM, then his question might have been, how to I use my scope or meter to check a speed sensor?

Oh? I've seen ABS-sensor "output" on a scope. I don't think most meters would register, at low wheel-speeds (think, jacking-up the wheel and spinning it by hand, or by belt-sander). Most DMM's are optimized for 60Hz AC.

Dunno about with a DMM but I can see the E28 ABS sensor pulses with a Simpson 260. The needle bounces visibly.

I don't know if the newer systems have any different sensor outputs although I know they now have much more sophisticated actuators.

--scott

Not over here they aren't.