About 18 months I retrofitted side object detection to my 2011 XF. It worked quite well until recently when the right side stopped working rendering the system inoperative even though the left module still works. I bought another module (used) and installed it on the right side. I've tried to program the module with SDD but it isn't working, giving a communication error. Here's what I think could be the cause:

1) The replacement module is faulty
2) There is a problem with the wiring
3) SDD or the cable have a problem.

I'm fishing for suggestions about how I might best go about diagnosing the problem. I've tested the right mirror and the LEDs work, and both LEDs in the right mirror illuminate briefly at start up, so the wiring in the door is good. I know that the left radar module is good. I could swap that onto the right side and see if I could program it with SDD. If that were successful, then it would suggest that both the replacement right hand module and the original right hand module are both faulty. It were unsuccessful, it would leave me with either a loom problem or SDD problem. My SDD appears to be working okay but I'm not sure how to determine if it is or isn't. Any suggestions about how I should proceed? Thanks