SOLVED!!!
Car was in ESP road test mode. This is DIFFERENT from turning ESP or traction control off using the procedure we're familiar with in the hidden service menu in the cluster.
ESP road test mode can only be accessed using a good scanner or mercedes's diagnostic system (star xentry). At least that is the way I understand it. I got into ESP road test mode using my icarsoft MB II scanner. This road test mode is only needed if you replace the yaw sensor, which is one of the ESP system sensors. It is mounted under the center console. The icarsoft MB II scanner has no way of turning off the ESP road test mode. The only way is to do the road test SUCCESSFULLY if you want to turn it off.
On our cars, we don't have an ESP off button, so ignore that part of the procedure that is online. If searching online, you'll find the road test procedure. Basically, you go to a parking lot, turn off the car, then turn it on. Right after, you drive at about 10 km/h, turn left at least half a turn and do a quarter Circle, then turn right past Center more than 90° to the right, and do another quarter Circle. In my case, I just drove the car around the neighborhood and did a few turns to either side and that turned the light off.
Now let's back up for a minute. Why was I messing around with the scanner? Because after trying to change the clutch I started up the car and I got an ESP error when I drove it. It turns out that when I disconnected the steering shaft at the steering box input shaft I at some point turned the steering wheel with the shaft disconnected. I was careful but must have done it without realizing it. When I started to diagnose the error with the scanner, I noticed that my steering angle sensor was reading 360 degrees. It didn't look right, but I was so sure that I hadn't messed up the alignment, that I didn't worry too much about it. I tried to reset the steering angle sensor, but I wasn't able to.
For reference, to reset the steering angle sensor, you basically start the car, turn the steering wheel all the way to the left to lock and then all the way to the right to lock then turn it back to Center, and turn off the car. But this only works if your steering angle sensor is only slightly off. In my case the steering angle sensor was a full turn off . I had no clue at the time but this is why I was still getting the steering angle sensor error after clearing all the codes, and then driving the car.
At some point later in time, I went into different menus and ended up going into ESP road test mode by mistake.
Because I messed up the alignment of my steering angle sensor, I was not able to do a successful road test. So I had two problems. I had the computer looking for a successful road test, but at the same time because the steering angle sensor was a full turn off, the car was reading the sensors saying that it was going straight, but the steering sensor telling it that the steering wheel was turned.
I finally decided that the reading from the steering sensor was proof that I did mess up when I connected the steering shaft. I had two choices, either disconnect the shaft at the Box and turn the steering wheel till the reading was at zero, or I was going to have to remove the steering wheel , and correct my mistake there, by resetting the position of the steering angle sensor. I chose the safe route because you don't want to break the clock spring inside the steering angle sensor. So I decided I was going to have to remove the airbag and steering wheel and reset the clock spring. Checked a few YouTube videos to help me along the way.
For reference, to reset the steering angle sensor mechanically, you turn it gently all the way counterclockwise, till it stops, then turn it about two and a half turns and align with the bolt bolt holes. There are YouTube videos on this.
Finally when everything was put together, my scanner confirmed that the steering angle sensor now read 0 degrees. I still had the ESP road test on. But after fixing the alignment of the steering angle sensor, I was able to do a successful road test and all the lights went off. I later checked for codes in the scan tool, but everything was clear with no faults.
Bottom line is this. Double check the steering angle sensor reading using a good scanner. This is especially important if you find yourself in ESP road test mode, and cannot get out of it. If the steering angle sensor reading is just slightly off, do the simple steering angle reset procedure by starting the car and turning the steering wheel lock to lock. Then you can do the road test. If it is a full turn off or more, then something was disconnected either the steering shaft to the steering box or maybe the steering wheel at some point and you'll have to access the angle sensor behind the steering wheel and reset it to Center. In that case only then you can do the road test.
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Tag: stuck in ESP road test mode? Double check steering angle sensor reading.
