Friends, thanks for all the excellent advice. I will check all the things mentioned. @Nippy I'm sorry, but I don't have a Windows computer with Protune, and if I had, I'm not so good with computers, so I'm not sure if it would be of any help.
I've collected some courage and will start searching again to solve this problem.
I see in the parts book five ground connections at which the two looms are connected to the chassis. I've found one under the bonnet just behind the engine. From the drawing, it looks like the speed sensor has earth on that spot. But does anyone know where to find others?
I also see three wires in the chassis loom drawing at the speed sensor. YB and YR both go to the engine/chassis connector. Does anyone know where the YK go to?
YK121 (yellow/pink) is one of the three wires from speed sensor and seems to be the shared signal. To this end it's joined to three other wires in a "bomb tail (as shown in Roger's pic) at a point 50 cm from the main chassis loom where stalk, ignition switch and immobiliser sub looms split off, so likely in the dash or fusebox area. This connection allows the speed signal on yellow/pink wire to be shared with ECU (yellow/white), TSM (yellow) and speedo (pink) wires.
The speed sensors other two wires, yellow/black and yellow/red, both go to ECU via chassis/engine connector as you have noted. Note there are NO chassis/ground connections directly related to speed sensor therefore.
Hope this helps Laurens.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone
