When you say they show no resistance, do you mean your meter reads all zeros? Or does it show infinite resistance, ("OL")?
The new ones on my bench show infinite resistance due to the nature of the circuit inside the sensor tip.
Expecting to see an AC voltage when you spin the wheel is not valid, from what I make of the circuit. There is nothing in the sensor that would generate an AC voltage.
The ABS module sends 12 volts to the sensor. As the teeth on the tone wheel pass the sensor tip, the 12 volts and the amperage are changed. This changed signal is sent back to the ABS module.
It's likely one of your sensors is not getting the 12 volts the ABS module is sending to it.
2008 Unlimited Rubicon Automatic