ECU ECU coding coding wires wires (where (where fitted) fitted)
Some vehicles equipped with Motronic 1.5 has ECU pins 20 and 21 allocated as coding earths. The open circuit voltage at
these pins is at the 5.0 volt reference level. Connection of the pin to earth indicates to the ECU that the vehicle is equipped
with certain equipment. The non cat vehicle will have pin 20 connected to earth and the catalyst equipped vehicle will have pin
20 open circuit. The vehicle with AT will have pin 21 connected to earth and the vehicle with MT will have pin 21 open circuit.