04 bonneville won't stay started

[Drive24]

starts up and idles smooth
runs a couple minutes then shuts off and once in awhile it wont start at all.
took it to a mechanic and he found some wires going to the spark plugs that were chewed on by mice. he replaced them.
it doesnt cause a check engine light to come on but where he test it, it comes back with a code for the ecu.
he was gonna replace the battery that is in the ecu.

ANY IDEAS??

[Jrs3800]

No battery that I know of in the PCM... as well the PCM is a sealed unit..

I think you need a dealer to have a glance at the car.. You might have some other issues..