Turn C2401 to disable. Then go to DTC Test Enablers and set any associated DTC test to "X:Non Reported". Then go to DTC MIL Enablers and set any associated DTC to "No MIL". You can also mess with the B1502-B1505 but you shouldn't need to.
EDIT: I explained the procedure for an LLY because thats what you have in your signature, but now I see you put LBZ in the thread title.
For an LBZ, the disable/enable table is B1501. You can but shouldnt need to adjust B1502 thru B1525 to keep it from running test as well. Then go to DTC Enables and set every associated code to X: Not Reported, No MIL