Explained by self 😀 jojojo
Step 1 – Insert debug breakpoint
Execute Transaction SE37 within Function module ‘AUTH_CHECK_TCODE‘, click on dysplay and insert a break-point the ABAP code line ‘if sy-subrc = 0.’, straight after the call ‘AUTH_CHECK_TCODE’ id ‘TCODE’ field tcode command.
Step 2 – Execute your desired SAP transaction code
Execute your tcode and SAP should go into debugging mode and stop at your break point. If it doesn’t type /h into the command line field(where you enter transactions) and press enter, then try executing your transaction code again. If it stops at a point which is not where you inserted the breakpoint in step 1 keep pressing F8 until it gets to it!
Step 3 – Change SY-SUBRC value
When the code reaches the ‘if sy-subrc = 0’ statement, sy-subrc should have a value not equal to 0 if you are not authorised for this transaction. Change this to 0 using the usual method relevant to your system (i.e. by clicking on the change pencil icon, change value and press enter). When value is changed press F8 to continue the SAP program on its way.