Having spent several hours researching last night I now believe that this orange/black input has three functions. On an auto it provides a straight to earth (0v) solution which in conjunction with the road speed sensor tells the car when it’s come to a stand still and to raise the idle by 100rpm if in neutral or leave lower if in drive to avoid gearbox drag. On a manual it’s supposed to prevent ‘confusion’ by using the resistor to tie pin 34 to 5V thus telling the ecu not to adjust the idle speed.
It’s just possible that with pin 34 floating it will attempt to change the idle speed by opening the stepper motor and cause a stall.
So testing the road speed sensor is on the cards today.
