Corsa-B.uk - Vauxhall, Opel and Holden Corsa B Owners Club

how do i change a crank shaft sensor on a corsa b 1.4 16v ?

Unbolt it. It's down below the timing belt cover. You get at it from under the car.

the crank cog is in the way can it be taken off without removing the cog? its the silver sensor and not the black one and it seems to be stuck on the bracket.

It comes off away from that "cog". Spray it with releasing fluid and let it soak for a while. Then lightly tap the bracket until it moves.