I usually test Hall effect sensors by breaking into the circuit at the connector and measuring current (in series with the sensor). They usually switch between 8 and 16mA as the wheel is revolved. Take care not to reverse the polarity to the sensor as they don't like that.
I have had several now where the signal measures good but the ECU still cannot see a speed reference. I think this is unlikely in your case, I would say it appears to be a short circuit sensor causing the ECU to shut down supply to it.
Shaun.