I have now the same issue, ct200h 2011
Car rattling while idle or low speed when the engine kicks on ,
works perfect when only the battery drives car
thought is the spark coils, found that 1 was faulty, but even after replacement its still rattling
went to lexus centre, they didn’t yet diagnose, but they think is the EGR, doesn’t quite make sense to me though, the rattling noise is far worse than just a clogged egr
waiting on the lexus centre to tell the issue, but would want to see if anyone else had this kind of issue and how the solved it
I’ve done a diagnostic at home and all came clean so it is deff something mechanical