2000 Lexus ES 300 dash lights flashing

Computer problem
2000 Lexus ES 300 6 cyl Front Wheel Drive Automatic

Let me start by saying I am a mechanic. In our shop today one of the guys replaced an alternator and battery on the above car. Upon completion he told boss that several lights on dash were flashing. The boss has now given it me. I have confirmed that the following lights arer flashing: cruise control, abs, air bag and I believe it was the vsc lights. I have checked the ecm, bcm, srs, cruise control and abs modules for any codes using a launch x431 scan tool. None were present. While the tech won't admit it the rest of us believe he may of reversed the terminals when he initally installed the new battery. Prior to giving me the car my boss had original tech check all the fuses. He said they were all good. My gut tells me he may have blown the bcm, as I am looking for common thread in my mind and have not looked on all-data as of yet. My questions are : am I heading in the right direction? Is there something I should be looking at? Please help or atleast give direction. We've never had anyone do this before and are not sure how to proceed.

Thank you
Mike