I was doing some work in my Gen 1 CRV and I pulled the battery for 2 weeks, put it back and I got the flashing green key light on the dash.
The car wouldn't start for 20mins and then out of the blue went back to normal, the green key now disappears a sec after turning on the ignition like normal and it starts fine.

Is this behaviour normal if you pull the battery?
And if so what's the technique to pair the key with the vehicle again other than my random method of trying to start it every 10mins or so?

 

Anyone have any idea?

 

Yes this is normal

 

That's good to hear, any idea why it happens?

 

I dont have the internal schematic reason but Ive personally witnessed this in three different honda/acura models. My best guess is the flashing green key is letting the user (You) know that it is accepting the key. The BCM (Body Control Module) is the place where your car keys chip info is stored so if you ever had to replace the BCM you'd have to get your key's programmed to the new one or your car won't start.

 

I know that much but why would it forget the key after the car battery was pulled and then 30mins after the battery is refitted magically remember it?