Issues with speed sensor

[anso-engineer]

Hello, I have ZAZ Sens car (very similar to Daewoo Lanos). Before yesterday I saw that at the dashboard speedo showed 200+ km/h at the idle. When I started to move, it jumped from the zero to max randomly, but mainly stayed at zero.
Yesterday, I saw the same behaviour, additioanlly got 0501 error and check engine light appeared.

I disconnected speed sensor socket and decided to the check amount of voltage which came there from the harness. It appears only with turned on ignition, which is ok. The strange thing I found, that with stopped engine and enabled ignition only, signal wire throws 10+ V. I thought normally it should gives 0V isn't it?

View attachment 149576
Here how this sensor looks like, it based on the Hall effect as I know:

 

[rjenkinsgb]

As it's an active (powered) sensor & presumably a digital output type, the output will be high or low depending if it's over a tooth or a gap on the gear is senses, even when stationary.

The ECU side also likely has a pull-up resistor for broken wires sensing - eg. if the normal signal is 0V <> 5V, going to 10V indicates a fault.