[Koolstude]

I've had the traction control light and the ABS light come on, the car seems to loose a bit of power, the radio volume dims a bit & the speedo stops working.
As for the cruise control not working - I've not tested this.

I've also had the same thing happen with the traction control light and the dynamic brake control light (the yellow exclamation mark) coming on.

This is sporadic.

Is this likely to be a faulty sensor or something major like the ABS unit?
Could the loss in power mean the brakes are being applied a bit by the ABS unit?
Will disconnecting the sensors cure the problem temporarily until I can get it in to be repaired?

 

[Ronnie]

Have you checked the charge rate at the alternator?

Also the ignition switches are known to play up on e39s

 

[mrbarry]

I had much the same. The abs was cutting in at any speed and braking level, traction control kept cutting the power and the warning lights finally came on. It was a dirty abs sensor. The sensors are basically read switches that pick up a load of ferrite sections in a rubber band fixed to the hub, any iron filings sticking to the magnetic parts will tell the abs ecu the wheel is stationary and it will assume it has locked. This makes it try to unlock it by applying the abs system. Also as it thinks the difference in wheel speed front to rear (front undriven and thus reference) is too great it assumes the rear wheels are spinning, at this point the traction control cuts power to try to stop it. After a bit it realises its not working and goes into fault mode.

First step get the fault codes read. This will tell you the wheel to start looking at. In my case the front drivers side, on strip down the bearing was a bit tight and very rough so I also replaced the front wheel bearings.