2002 Saturn SC2 BCM Reprogramming

HI
i OWN A 2002 SATURN SC2. HAD AN ISSUE WITH THE BCM LOSING MILEAGE, WENT TO 000000. THEY SECURITY FINALLY WOULD NOT READ THE KEY AND TUMBLER ANY MORE AND NOW WILL ONLY START FOR A FEW SECONDS THEN THE PCM SHUTS DOWN THE FUEL.
I BROUGHT THE VEHICLE TO A GM DEALER TO HAVE A USED BCM PROGRAMMED TO THE CAR. THEY TOLD ME THEY TRIED TO PROGRAM IT BUT IT WONT TAKE SO I NEEDED A NEW ONE. I PURCHASED A NEW BCM AND HAD THEM PRGRAM IT. THEY ARE TELLING ME IT HAS A SECURITY ISSUE AND MAY REQUIRE A NEW KEY AND TUMBLER.
THIS WAS ALREADY REPLACED BEFORE THE BCM ISSUE. SO THERE TELLING ME THERE HAS TO BE SOMETHING IN THE WIRING.
I AM HAVING A HARD TIME BELIEVING WHAT THERE TELLING ME SO I PICKED THE CAR UP AND BROUGHT IT HOME.
THE MILEAGE THAT WAS ON THE CAR WITH THE ORIGINAL BCM WAS 138421KM. THE NEW BCM HAS 174000KM SHOWING ON IT. THEY TOLD ME THEY DONT PUT THE MILEAGE IN THE CAR, IT PULLS IT FROM THE CAR.
IS THAT TRUE? I WAS OF THE UNDERSTANDING THAT THE MILEAGE IS STORED IN THE BCM ON A SATURN AND NEEDS TO BE TRANSFERED TO THE NEW ONE ALONG WITH THE VIN, ETC.
WHEN I TRY TO RELEARN THE SECURITY SYSTEM IE. THE TURN KEY ON, CRANK ENGINE, WAIT 10 MINUTES, ETC. FOR THREE KEY CYCLES. THE SECURITY LIGHT JUST KEEPS FLASHING NO MATTER HOW LONG I WAIT. IT DOESNT COME ON STEADY OR GO OUT. JUST KEEP FLASHING.
I HAVE CHECKED THE 3 WIRES THAT COME FROM THE KEY CYLINDER TO THE BCM WITH AN OHM METER. THEY ARE NOT BROKEN AND I DO HAVE A RESISTANCE READING WITH THE KEY TURNED BETWEEN THE YELLOW AND BLACK WIRE SO I AM ASSUMING IT IS WORKING CORRECTLY.
ANY HELP WOULD BE GREATLY APPRECIATED.