''I've checked the voltage at the VSS connector near the wheel. The R/Y shows 4.99 volts, and the W/Y shows 4.88 volts. This is the same as on my other car.' unquote.
The W/Y is probably the signal and will really need an oscilloscope to measure when the car is moving. There would be pulses so a meter should read 2.5V when moving. A duff TSM could pull that signal permanently high so you may see 4.88V when moving.
Not sure where that info comes from Alister but the wire colour codes mentioned do not relate to those of the VSS (speed sensor) on the M3W
Originally Posted by AlisterW
Proof is to disconnect the VSS signal going into the TSM, but leave it going to the ECU. Maybe you could jack the car up and run the rear wheel off the ground? I guess the VSS is on the gearbox output shaft somewhere.
Note that Laurens has already proven the front wheel mounted VSS itself works ok with both the TSM (cancelling indicators below 10mph) and Speedo giving normal reading. Furthermore he has swapped out the VSS from his other car with no change. It's only when this same shared signal is connected to ECU (as normal) that his idle problems appear although TSM and Speedo still work correctly with speed signal.
@Laurens it may seem a desperate measure but I would be tempted to very thoroughly check the shared speed signal bombtail again. I know you said it looked ok in the crimp. I would particularly check the YW wire out of this tail as well for vibration induced partial fracture of copper strands within.
If nothing found then maybe try the suggested removal of this ECU speed feed YW wire. If driving tests reveal no negative issues with idle under a variety of driving conditions then it could be assumed it's not needed on your particular car.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone
