2002 E320 isn't safe to drive, back end is completely unstable

[ravensfan8448]

Hello! I have returned here seeking guidance. The folks here have been a tremendous help to me in the past with regards to my 2002 E320, and I'm hoping you guys will be able to help me out again.

I put together video for your viewing pleasure! First 3 minutes summarizes the situation and demonstrates the issue, the rest is me messing with my STAR diagnostic system. Might be a bit easier than reading my ramble below. https://www.youtube.com/watch?v=JSXK3tvuuh4

I was on my way to work yesterday, and as soon as I turned left across the intersection and started getting on the gas (maybe 35mph or so) I felt the back end of the vehicle start to move horizontally into the lane to my right. It should be noted, I didn't hear any bangs and I didn't feel anything mechanically go wrong from the drivers seat. The only thing I heard was all the error messages popping up on the dash (ESP, BAS, ESP). I had driven about a mile and a half completely normally prior to this event. I tried to correct the sway and the whole car started fishtailing before I was eventually able to get it to a stop on the side of the road. I stuck my head underneath expecting fluids to be leaking somewhere, or broken parts hanging from somewhere but everything appeared to be intact. I managed to drive back home with the hazards on, going about 15 mph the whole way. The backend felt like it was on ice skates the whole time. I had to turn the steering wheel about a quarter turn to the left to remain going forward in a strait line.

I plugged in my STAR system and cleared all the old codes. Once I run a new test, the only fail I get is in the ESP system for the N49 steering angle sensor. All other errors are in driving irrelevant categories (Partronic system, Instrument cluster, etc). If I go to test the steering angle in the STAR system though, the angle values seem to be showing just fine so I'm not sure what the problem is there. When the quick test is running however, once it gets to the ESP section, it triggers the ESP warning light on my dash. The only warning light that shows after I first start up the vehicle following this event is the battery/alternator warning.

Right now everything appears to be mechanically normal, so I'm not sure what the issue is. My brakes and steering system seem to be normal, the backend is just so unstable I can't safely drive the vehicle anywhere.

I'm going to attempt to test the wheel speed sensors somehow (STAR says I need to get the wheels turning at least 3km/h in neutral and right now I don't even own a floor jack). Past that I'm not really sure what steps I should take next. If anyone has any ideas for me I am more than happy to give them a try, thanks ahead of time.