I am trying to program brand new MX (433MHz) sensors installed onto a second set of wheels for a 2016 Mercedes C-class. I manually entered the ID (clone the stock sensors) in programming mode, but get an error that says "write file error (-1)". It appears to at least find the sensor, because if I try very far away from the wheel, I get an error "without sensor (-2)".

Since I never got any response or solution from Autel Support, I found the solution and will share with the forum in case someone else has the same problem. The issue was that there cannot be tire pressure while trying to program the sensors. The TS401 says (in programming mode) to do this while the tire is below 70 KPA (~10 PSI), but really it needs to be almost 0 PSI. So I released the air out of the tire until the pressure was very close to 0, then programmed.