ABS Break lights ON

[lion2000]

I have a 2001 X5 4.4i. 130 miles after the two front axle assembly replacement, ABS and Break light comes on, Speedometer stopped, Techometer momentarily working, temp needle goes to max. After some web search, I decide to test the ABS Speed sensors myself.

After disconnecting the sensor connector in the wheel well, I measured the voltage coming out of the ABS module:
0V - ignition off; 2.8V - ignition key pos 1; 2.5V - ignition pos 2.

Measured the resistance across the sensor terminals:
Left front - 8.5MOhm; Right front - 8.2MOhm.

Attached a scope to the sensor output, spinning the front axle, I do not see any pulse coming out of the sensor.

Removing the sensor from the hub assembly, found iron powder on the sensor tip. cleaned sensor tip. Placing a magnet at the tip of the sensor and moving magnet, barely see any voltage change.

Looking into the sensor hole, spinning wheel, I do not see anything different after 360 deg rotation. It was just a metal drum. So what causes the sensor to pickup signal?

Now I am wondering if the sensor is bad, or installation of the axle causes the hub assembly to fail?

Thanks in advance for your help!

//Leo