No crank / no start

My brother in law was driving his car the other day and the oil light popped up on the dash board and the car completely shut off on him. About 10 minutes later the car started back up but was real hesitant and had no power. The car shut off again after a few seconds of driving. I had it towed home and began to check everything out. I've been working on cars for 2+ years now and done multiple tests and went over everything. I hook up my solus pro and no codes were present at the time. Next I tested the battery and it tested good with 12.9 volts. I took the altinator out and took it to my shop and tested it and it passed the test. Next I moved on to testing all of the fuses and relays and all came back fine. I swapped out the starter since the old one just clicked and didn't try to crank. Got the new one in and did the same exact thing.I connected my scanner to the car again and found a history code for crank sensor a and b. I swapped out the crank sensor put the car back together and still has the same issue. When trying to crank the starter just clicks and all electrical components shut off and come back on. Once again I went back into my scanner and a message appeared "unable to communicate with ecu. The car is alarmed with this system, ob2 plug is fine. No connection." I went back and swapped out the ecu relays and fuses and went to try it again and still cannot connect. I am so confused on this and can't think of any other test to run for I have done pretty much everything that should have been tested. Any help would be great! Thanks Will