W202 ETS light and fuel gauge..

[moonloops]

Got a couple of niggly problems, firstly the fuel gauge is erratic and only reads properly when the tank is full. Once it goes below 3/4 it reads randomly and stays at zero a lot. I did a bit of researching on this and often it is the sender(s) that gum up. I've ran through 2 tanks of Shell Nitro and also used a few petrol additives and things have improved but still not perfect - anything else I can try? If I need to replace a sender how easy?

Also the ETS light is on (traction control) there are no ABS lights on and ABS works just fine so I'm not sure where the problem is - unlikely to be a wheel speed sensor ??

thanks in advance.