Hi I don't think the ECU inhibits cranking. I wouldn't take the engine apart, seems a bit extreme unless something tells you you have a problem with it. You could do a compression test on all 6 cylinders that would tell you if you have an engine problem. Check you have a spark on one of the spark plugs by connecting to the HT lead and placing against the engine, then crank, just dont hold the lead or plug whilst cranking. Have you checked to see if there are any codes in the computer via the OBD port ?