If the EML isn't on, that's a sure sign that power isn't getting to the ECU *OR* the ECU is sometimes failing it's checksums on boot, however that should leave a code logged regarding Internal Checksum Error and I'd expect it to leave the EML on, that is pretty unlikely though, I'd go with the no power option.
If the immobiliser is blocking start, the EML will be on, I can tell you that this is not an immobiliser issue. Does the EML ever come on? Remember it doesn't look the same as most other cars - it looks like this:
https://i.ytimg.com/vi/ieINjwpaIoI/maxresdefault.jpg
If the immobiliser is blocking start, the EML will be on, I can tell you that this is not an immobiliser issue. Does the EML ever come on? Remember it doesn't look the same as most other cars - it looks like this:
https://i.ytimg.com/vi/ieINjwpaIoI/maxresdefault.jpg
