i have a 02 odyssey it wont start the key light doesn't come on (i just changed engine) it did start and ran for a while then quit i read there were relays behind fuse box (stupid i thought) i tried to pull out a square plastic box found out it was multiplex the dash lights (d flashes and engine light ) no key light.
NOW here is something WEIRD when i plug in my cheep code reader it starts and drives
please help

 

Fuses are OK?

 

Check all the grounds! I missed one stupid ground on my build and nearly tore the engine apart because it ran like ****, hooked up the ground and it runs like new! Make sure all connections are clean and have good contact.