to reset your ECU, you have to do a little more than just disconnect the battery and plug it in again.
Disconnect the battery and leave disconnected for about 30 mins.
connect the battery back up and go put the key in the ignition.
Open all the doors, boot and bonnet and turn the key to get all the lights on. (This i am told alligns the throttle body)
Close all doors, bonnet and boot and get in the car.
Start the engine and turn everything electrical on, opening the windows full and then back up again. (This teaches the ECU what the maximum amount of electrical output maybe required from it.)
Turn everything off apart from the car and go for a spin
I personnaly wouldnt bother reseting my ECU as a matter of course. I only ever donr this when my fault light came on and it was my MAF sensor. I reset the ECU to see if it was a
problem with MAF or a faulty sensor.