polo1.4 Twist 2004 running rough code P0019E

[Megamast]

Hi
The car started to run very rough like it was running on 2 cylinders and began sending out code P0019E. I found that all 3 glow plugs were open circuit so replaced them. Still the same condition running rough but starting was getting a bigger problem. I swapped the cam sensor and the crank sensor to try and get rid of the P0019E but it remained and everything stayed the same. I can actually remove the cam sensor connector whilst it is running and it keeps running rough as before. I understand that the Crank sensor drives the tacho which indicates about 800 rpm when the engine is running and the engine speeds up fine when i press the accelerator.
This is a strange one. When the engine is running the code will be present if i clear the code with the engine running the engine will appear to fire on all three cylinders for maybe a second then reverts back to running rough so the P0019 seems to indicate the fault that is causing the rough running.

I have the engine light on and the glow plug light flashing. Also changed Brake light switch which was faulty. Engine still running on 2 cylinders plus code 19 still up.

Hope this makes sense to someone!

Any help would be great. Thanks