The dealer did not change the belt if it was done under warranty.
You will have to pull the timing belt to replace the crank sensor which means removing the drive belts, crank pulley, belt tensioner and timing covers. To remove the covers the upper engine mount needs to be removed so you can raise and lower the engine to get ot the bolts.
The crank sensor has a shutter wheel that is around the crankshaft and runs through the gap in the sensor. The teeth come off the timing belt and land in the bottom of the timing cover where they are caught in the shutter wheel which forces them through the gap in the crank sensor cracking it. The sensor works sometimes=mes after that and totally fails after a short time.
It is very difficult to hold all the cams in time as you install the belt, I use a helper to hold the back two while I align the belt. Book time is about 3.5 hours but the first time is more like 6.
The procedure to replace the belt and sensor is below.
Once the belt is off remove the two bolts holding the sensor and install the new sensor. Route the wire EXACTLY as the old sensor wire was run or it will get cut by the timing belt
If you want to double check that the sensor is not putting out a signal you will need a voltmeter
Let me know what I can do to help you with this