Why won't ABS Fault stay cleared?

Question

I replaced the front left ABS sensor on my 2008 Ford Focus, then reset the fault w/ an OBD module & phone app.  I can reset it but after about 1/4 mile the fault light comes back on. It shows a "chassis fault, which comes up as code C1233.  
Why will this not stayed cleared?
Steve

Answer 1

There are what they call hard fault  code and soft code, what you have is a hard fault code, What the ECM does is look for open circuit short circuit and rationality. So you have either a open circuit or short circuit these would be hard code set faults