(G) CAT issues/How can i find out the engine code of my scudo

Hi
Have a 01 Y Scudo JTD, pretty sure I have a blocked or collapsed CAT. Low power LOADS of smoke whistling from what i assume is wastegate and engine warning light.

Hoping to get someone to check code tomorrow (assuming it is exhaust manifold pressure sensor - which is opening the wastegate) I need a new cat.
Ordering one from a extremely price competitive supplier in Kent requires that i can check the engine version.

Can someone help me out with a simple way to check the engine code?

thanks

'zul