how to display DTC?

[jettacelebration]

Hi

I need to how I display DTC ?

I some budy know the jetta 1994-1995 OBD1 have a OBD adapter used to access blink codes. and the adapter is located beneath the rear seat.

The point is when I put the adapter the books (service manual from bentley) say with the ignition key on!!! but I need to start the engine or with the engine off to read the code because I tried with the ignition key on but I dont turn on the engine and when I put the adapter the check engine light turn off and dont show any code. and I dont try with the engine on becouse it had the ECM result damage.

I some budy do this in the past please tell me is the procces is with the engine on becouse the book dont say (with the ignition key on and engine run)

Please some budy help me. Because when the engine is runing over 3k rpm the check engine light turn on but when the engine stay in low rpm the check engine light is gone.

Thanks for your help