2001 Audi S4 ABS engagement, electronic buzz and shudder

Those codes would appear to be in conflict with each other - system too rich and system too lean.

The hard shifting is the kicker though - that points me straight at the MAF sensor. My bad MAF on my S8 gave me that exact symptom, with a very hard shift 1-2 under full throttle.
Mine also gave me ABS and Traction fault lights, as stability control uses engine load data provided by the MAF.
So I'd be replacing the MAF.

I would also be checking all your vacuum hoses and possibly replacing them all regardless. The Audi cloth covered vac hoses of that era would be brittle and liable to break by now.
Silicone hose is a good replacement choice, though thick walled rubber hose (1.6mm 1/16" wall thickness) is also good (avoid the thin walled stuff (>1mm)).

-Don't worry. Even the abs is not function properly but the basic brake still work like normal car.



Good luck



Mai

Under the hood there should be a fuse box, it's going to be one of the big fuses, had the same problem, 01 Tahoe. Found out it was a front bearing assembly. I replaced and it works fine now. Be carful as you will have no abs once fuse is pulled and FYI the abs light and break light will stay on as well. Good luck

Just food for thought, remove the distributor cap and have somebody else crank the engine over and see if the rotor is turning if its not, I'd look at timing belt/chain. My observations are usually timing belts break when starter first engages or when engine shuts off, as most strain on timing components are when first start rotating, or a backfire occurs, seeing as was running fine when you shut it off id check this first, then control module, hope that helps you out.

If the car shudders all the time stopping it could be a rotor out of round sometime this happens with new rotors, they should replace them under warranty. But if it is more like abs shudder then they could have damaged a sensor at one of the wheels, the sensors are used for abs and traction control.

I had the same problem. the jerking breaking and pulling to one side, but if u are going over 70 miles and that happens to you, you better start praying cause it will **** so hard that its hard to control. the yaw rate sensor (prox $400 on line) needs to be replace and adjustment (i beleave only the dealer can adjust). What I did to solve the problem is to eliminate the sensor ($0 cost). now my SUV drives and handle just like a regular truck without traction control. Toyota is not helping on this matter and dealers just dont care. I will not put my family thru the same scarry ride. My solution eliminate the sensor, the light is on @ all time but in return a smooth ride. Im not telling you to do what I did, but Im telling you it is the Yaw Rate Sensor. Good luck.

It may be a calibration issue. The sensor doesn't know what is considered slow or stop., Yes,your right, a computer thing.

YOU NEED A SCANNER TO MONITOR THE WHEEL SPEED SENSORS. THE ABS IS SENSING A SKID AND THE ABS IS ACTIVATED WHEN THIS HAPPENS. THERE MAY BE A CODE FOR THE HUB THAT IS CAUSING THE ABS TO ACTIVATE.

CHECK THE WIRES FROM THE SENSORS FOR BREAKS OR CHAFFING. AN OHM READING OF THE SENSOR SHOULD BE 850-1200 OHMS, AND AND A-C VOLTAGE READING SHOULD BE 100 MV WITH YOU TURNING THE WHEEL BY HAND.

RATE ME, PLEASE

Pads worn down to the break wear pad which sings or vibrates when pads need replacement.
Get new pads, ceramic and if you get the BEST ones, the will replace them FREE, forever ;-)
($100.00 at Midas, Brakes+ or the like and takes 20min)

Hi Tino75,
I suggest that your vehicle needs to be taken for an electronic scan....Your problem may be to do with the ABS pump or a loose wheel bearing...please let us have more imfo
Regards
Johngee10