Hopefully i can help..
Sounds like a speed sensor/crank sensor fault - normally that sensor is used by the ecu aswell.hence when it drops out on the dash the engine warning light comes on..ideally it would be worth getting the fault codes retrieved diagnostically to back that up wise before consdiering replacement..but normally its down to that sensor dropping in and out,failing in itself causing the issue you have...I do hope this helps
Sounds completely logical, where is it fitted??
Ok..normally these are two places the first being at the top of the bellhousing usually on the auto's if i recall the other is located just above the crank pully at the front of the engine - it only held with one single bolt...unfortunatly there arnt many pictures to send over..but normally its the crank speed sensor that can cause that..the cam sensor isnt located on the engine but as part of your injection pump..so if the cam sensor is causing this hence why i say diagnostic first..then its a new injection pump....