Try the following

1) Disconnect the negative battery terminal for about 10 minutes and reconnect (by doing this you are clearing all error codes in the ECU)

2) Drive the car and see if the fault reappears (doesn't really matter if it does or not)

3) With OUT turning the ignition off measure the Duty cycle between pins #2 and #3 on the x11 diagnostic socket. If this is giving a continuous error code report back

Could be the road speed signal transducer (Could be other stuff - the point is to measure the error codes in the form of Duty cycle)

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!