This Partial Change Correction (PCC) feature is relatively new to the SAT IV’s programming. So if your SAT doesn’t seem to be responding to the STO + MSR command it’s program may need to be updated. Being able to correct partial changes is unique to the AccuTuner. An FAC tuning has fewer partial changes (3) than any other tuning system, and yet it is the only device capable of correcting them. (Contains button pressing video).