Originally Posted by ozzy

Its not the IFZ that prevents the engine from starting its the HFM, the HFM is always locked until it recieves a CAN message from the IFZ, so as soon as you turn your ignition on, the HFM is powered up and then it waits for transmission on the CAN data bus.
The DAS infrared control module (IFZ) evaluates the transponder data transferred and, if valid, releases the engine control via the CAN data bus.
now if the key, transponder coil and IFZ were all working as they should and validation is then put onto the CAN data bus, then the IFZ has done everything it needs to do, from here on its up to the CAN data bus to deliver validation to the HFM, but if it gets to the HFM and the HFM wont accept validation (fault in HFM) the engine will not start.
As far as coding the HFM, this is refering to version coding i.e: what eng, what transmission, what body type, what country etc. when a new control unit is fitted these codings are directly transfered to the new control unit, If HHT (hand held tester) can't communicate with the control unit, you would then have to enter codings manually. these codings are generally YES/NO options. The IFZ would not be part of version coding because its not an option.
I realise this is all a lot to take in and understand but hopefully it helps