06 Chevy Suburban

I have an 06 chevy suburban in our shop with two codes a c0292 accelometer needs replaced and a c0074 code ebcm internal fault. The c0292 code needs a reflash by a gm service tech after install. Now heres the problem the gm service tech will not reflash unless he installs the part for $987.00 for the part and $450 labor charge. I installed the part at my shop for a cost of $260 for the part and $48.00 labor charge but I can not reflash. Is there something i'm missing here. I replaced a transmission model in a chrysler car and the chrysler tech reflashed for a charge of $50.00 with no problem with me installing the part. I am an ase certified master tech with 27 years exp.