Try both as Steve suggests - although the immo is part of the instrument cluster it is sometimes treated as an independent ecu from the dash.

Can you access the instruments at all?

To see if the engine ECU is communicating on the bus with immo / dash, use MVB's 125, 126, 127, 128 to see which systems are communicating with one another.
Did you carry out a full systems scan to make sure the rest of the systems are functional via the diagnostic interface?

The system functional path is KEY inserted > reader coil sends key signal> dash crosschecks key coding > OK > sends unlock message to engine > engine replies to dash> engine starts

The engine will have dual capability to communicate with the scanner via the K line on pin 7 or CAN on 6 & 14. When the bus is pulled down this can result in comm's with the engine only.

hth,

Jon.