Have Ford Questions? Ask a Mechanic for Answers ASAP
Hello and thank you for your question, The codes U1900 and B2900 and C1805indicate that the ABS module is having communication issues to the PCM just as the scan tool is having communication issues to the PCM. Start first with making sure the #11 fuse in the under hood fuse panel is in place and not blown. If the fuse checks okay the run the enclosed test steps in the link below. Copy and paste the link to your browser to open and view them.https://dl.dropboxusercontent.com/u/104923897/B1900%20Ot%2029.pdf
If you doing your testing right it sure sounds like it.
Try swapping it with a known good relay .