Hi all,
Got an X3 in with an unusual problem - when accelerating through approx 3200rpm the 4x4 traction control light will flash and the engine power is cut, almost like its in limp mode, but when you lift off the throttle the light goes out and normal operation is resumed until the next acceleration/light episode.

Car is fault-clear in all modules. Tried so far:

Steering angle sensor has been reset & calibrated
EGS reprogrammed with latest file
DSC reprgrammed with latest file
Gearbox adaptations reset
Tyre pressures checked & monitoring system reset
Battery voltage checked (13.51v at idle, 13.71v at 2000rpm)
Wheel speeds observed during fault condition but all appear equal and correct.

Anybody seen anything like this before or have any ideas?

Scoped the AFM and all is as expected....

We scoped the outputs of all four wheel speed sensors and the NSF one does not output a signal (well it does, but its only just above background noise and in the mV range).

We tested the voltage against that of the OSF sensor and the rear sensors and all are the same at around 12.5v and 0.5v on each wire (so wiring and voltage supply from ECU must be OK?)

We swapped the front speed sensors over and the NSF still exhibits no signal.

We 'wafted' a magnet across the tip of the OSF sensor and noted a pulse on the scope - same test on the NSF one results in no pulse.

Whats confusing is that if we have voltage, indicating the wiring must be OK and continuous and that the ECU must be outputing the voltage, why dont we have a signal pulse?

I'm thinking that there may be an internal fault in the DSC ECU that is dragging the signal level down, but thats a pure stab-in-the-dark.

Any more ideas?