The chip reader is a ring around the ignition switch.
If you stick the chip from the other key next to the ignition switch you will be able to use any key.
However if the car is stolen and the insurance company find you have effectively disabled the immobiliser (statistically unlikely, I know) they might not pay out.
Depending on the year and value of the car a replacement key might be better.
fred
February 2012
I can answer this question...
lost immoboliser key for vauxhall corsa have original ignition key with chi?
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