Z wont go into Diagnostic Mode
 

Hello, I am a new member, hello everyone, I have an NA 92 300zx
I'm having an issue, getting the car to go into diagnostic mode. I did the thing at the ECU where you turn the screw clockwise, wait, then turn it counter clockwise, also did the opposite. When that didnt work, I tried doing it by connecting the pins on the connector under the driver dash, that didnt work either. I cant find anything online, can anyone help?
Thankyou.