So this is actually my friend's 2013 Nissan Rogue. I am just the mechanic fixing it, but I don't have a keen eye or ear for Asian vehicles what's so ever. My skills sort of skill revolves around Ford, Chevy, Dodge, and so on...so he told me he was in Florida and after he had put it in reverse it would not move then it died and ever since it has been unsuccessful starting. Engine turns but no fire. After inspecting it I am lead to believe the computer may be fried. The first thing I did was jumped to check for codes. I tried my code reader and a Snap On diagnostic tool that's probably 1000s of dollars the Army paid for it. Each time it said it failed to link to the computer. Also, when you cut the ignition over his engine fans cut on full blast which is crazy. His diagnostic port shows no signs or tampering on the wires. I'm thinking the computer may be toast. I have checked all fuses and none have been blown. I'm thinking the computer is toast what do y'all think? I'm trying to help him out with higher urgency because this is his family vehicle and he's a soldier with a kid and another on the way. Inputs would be nice thanks!

Change the fuse that powers the obd port just for fun. The fans will come on if the ac is on, though they usually aren’t on high.

Is the gear selector in the correct gear? By that I mean does the vehicle recognize which gear the lever is in?

These vehicles are known for a crappy failure prone transmission but that shouldn’t keep it from starting.

If you do a new ecu you’ll probably have to go the dealer route to reprogram/program it. I’m not sure your snap on will do that though it might.