OBD Code - any idea where to start?

The old Glow Plug light has popped on a couple of times during the cold starts at about 1 mile from my house when I am sitting a T-junction and idling, the usual process of ignition off, then on, clears the problem and all is well for the 40 mile run to work, and I am only likely to see it when it has been cold (2 degrees or less I would say).

Anyway, just popped my Bluefin on and I got the code:

P0325 Knock Sensor 1 Circuit Malfunction (Bank 1 or Single Sensor)

I have no idea where to start on this one and it was the only code recorded, there are no others in the list.

I had the Injectors reconditioned about 6 months ago (done about 10 - 12k since they were done) and have not had the Bluefin on in that time so the Injectors have not been pushed.

Does anyone have any ideas where to start?

I appreciate your help.

Cheers