[Johnjj]

OK, my sons car will not start, at first ee had to jump start it with leads it did go, a few days later we tryed o start it but same again we had to jump it
We put ew battery in it and it I'd not start so we jump started it again went fine for a small drive but next day battery volts where right down and again we jumped it
So we changed the obvious thing from battery, the alternator but car would not turn over it was saying on dash engine system fault so we checked the wiring all good so we changed the starter motor and it still says the same on dash so we checked he wires on it all good but on checking the wires we seem what looks like a lose connector hanging down that as a L shape and looks like a push n type that would o on to some kind od sensor but. Can not see any where this may go any answers on this would be most thankfull

[NMNeil]

I believe the alternator is controlled by the PCM.
Assuming the car will start with a fully charged battery.
Grab a voltmeter and measure the battery voltage with the engine not running. Should be between 12 and 13 volts, the exact number is unimportant.
Start the engine and the voltage at the battery should be over 14 volts, again, the exact number is unimportant.
If it's not you may have a bad PCM, or the PCM may not be getting or sending a signal to the alternator.
Buy a cheap OBD2 scan tool and this will also tell you if there are any charging circuit related error codes.
But whatever you do, stop throwing parts at it before you do a diagnosis.

[Grimm]

That loose connector could be the culprit try tracing it back to see if it connects to a sensor related to the alternator or PCM, as that might sort out the issue.