No test instruments required. The code is generated by counting the number of flashes. Extract from VXON. "yer corsa's and astra's and zafira's it works for up to now and for people who dont know how do the "pedal trick" No need for Tech 2 or any sort of code readers and Most of Vauxhall dealers don’t know about this.... When you get into the car you know the key has 3 clicks first on for aftermarket cd player and whatever else and the second one the dash comes on third the starter kicks in before you put the key into the ignition Make sure that you Press the Break and the Throttle to the Floor ( max ) Then turn the key on until The dash board come on and DONT START THE CAR Wait 2 sec and keep the pedals Down to the floor the service light under the management light should start flashing it will flash 4 times leaving 2 second space representing each number Zero gets 10 flashes for exampleP0110 the light will flash ten times Break (2sec Or 1 not sure) then once, (2sec) once again, then ten if you have more than one code it will stop for a break then gives the next code however if you don’t have any code stored it will start Flashing and keeps on flashing until you release the paddles" However as you disconnected the battery the codes may have been cleared.