I am trying to get my daughters car to pass emissions inspection.Check engine light has been on for months but car ran ok so didnt bother checking it. Car failed inspection so must take care of this now. Turns out ecm fuse was blown.Put new fuse in and runs ok with no light but fuse blows again after a couple of days.Has happened twice now.What can cause this problem.?

Welcome to AF, you need a wiring diagram to see what is in that circuit and trace the harness down looking for a pinched wire, also get the code that might help. No short cut or quick answer to this.

Absolutely.

It's likely that one of the outputs from the PCM has a circuit problem or is shorted, but finding which of the numerous possibilities it might be would be a long and possibly fruitless process. It's fastest and easiest to retrieve the stored trouble codes and analyze that information to direct you in your search. Many auto parts stores will offer a code scanning service free, in order to try to sell more parts. If you take advantage of one of those, make sure to get the actual trouble code numbers instead of the generic description of the trouble code(s). Make a note of the code numbers and you can find further and detailed information on each of them - Right here.

Plan on having a good fuse installed when the code scan is performed.