hi there

Some weeks ago I heard a grunt noise (1 sec in duration) from one of the wheels and the ASR warning light popped up promptly and disappeared soon after.

But since a few days ago, it just keeps appearing, but without the noise it made during the first time.

How does ASR work and where are the sensors it uses?


Thanks in advance!

ESP warnings now as well

its the abs sensor isn't it?

The grunt noise is probably the pump engaging. It is failing some sort of self-test, and might not be a wheel speed sensor at fault. I had a faulty valve block on my Alfa 156 with VDC (Bosch 5.7 ABS with ESP, same as the Stilo).

Or, I suppose the sound could be the brake being applied to a wheel that the system thinks is spinning or sliding, since it has ESP as well.

I think the first thing to do is to check the wheel speed sensor rings for obvious faults (rust, debris), and then connect to MultiECUScan etc. for a diagnosis.

Has the steering wheel been off recently - is it possible that the steering angle sensor may need to be re-zeroed?

To answer your original question - yes, ASR is just software programming in the ABS unit. It uses the wheel speed sensors, possibly the yaw sensor and steering angle sensor, and can also request a reduction in engine torque from the engine ECU. Theoretically the 5.7 ESP can also apply the brake to the spinning wheel, transferring the torque to the other wheel, but in practice it doesn't seem to achieve that (perhaps yours is trying!), and just reduces engine torque instead.

I once timed a series of takeoffs on a race track with ASR off (in my first Stilo) and with it on. I can honestly say that the variation was within measurement error. Without ASR you get a lot more drama, but with ASR it's just as fast.

VDC/ESP (stability control) cannot be turned off. It will prevent the car from spinning or sliding, by braking individual wheels, and is quite magical. That's just software in the ABS ECU as well.

-Alex

Thanks alex

I only heard the grunt noise the first time the error appeared, not ever since. A faulty reading may explain that as you said The error now happens without any noise.

All wheels have ABS sensor or just the front ones?

spyshagg said:

Thanks alex

I only heard the grunt noise the first time the error appeared, not ever since. A faulty reading may explain that as you said The error now happens without any noise.

All wheels have ABS sensor or just the front ones?

Click to expand...

All wheels. To get to the back ones, you probably need to remove the brake discs. There will be a magnetic ring on the hub, a brown plastic material like a fridge magnet. It probably has ridges of metallic dust built up on it, which will wipe off (a bit surprising when you see it the first time!)

You can trace the wiring from the sensor to the connectors and make sure it isn't frayed or broken. They're generally reliable but it's always possible that a sensor coil has gone open-circuit - you can test for continuity with a multimeter. Of course, the diagnostic software would narrow the task down, as it will tell you which sensor is faulty and save having to check all four.

-Alex