Fi light on 9 flashes

On my way home the Fi light came on at tickover, i heard the engine revs die slightly as though it was going to stall and as i reved it the light came on.
9 flashes which is the Manifold Pressure Sensor to Rear Cyl.
I have checked the vacuum hose and electrical plug to the sensor and all seems well.
Anyone have any ideas on why the sensor is reading a fault other than the obvious sensor itself being faulty.
Also does disconnecting the battery reset the fault codes.

I swapped the rear Map sensor over with the front Map sensor today and the fault code now flashes 11 times [front map sensor]
So it looks like the sensor itself has broke, will ring the dealer and see if they have one in stock.