Yeh check ecu coolant and det sensors to start and obvious visual inspection on all 3 before going too deep .
The knock sensor fault relates to fault in wiring or sensor itself as simply a resistance value check by ecu, ecu logic doesn't cover knock detection via fault code .
Both MAF and ecu temp sensor can cause fuelling issues, ecu temp sensor can cause difficult starting, idle speed issues and fans to constantly run .
is a pdf in the useful links pdf file topic on coolant sensor test/functionality. few threads on knock sensor test. have a doodle and see how you get on .