The vehicle with AT will have pin 21 connected to earth and the vehicle with MT will have pin 21 open circuit
Bron: http://www.cardiagnostics.be/-now/Tech2_bestanden/Opel_Motronic1.5.pdf
Bron: http://www.cardiagnostics.be/-now/Tech2_bestanden/Opel_Motronic1.5.pdf