P0720 code is the Speed Sensor. It is located on the driver side end of the transmission. It is easy to replace approx $100 on rockauto.com and $140 at the dealer. Take of the drivers side front wheel and the plastic guard and it is visible just forward of the axle on the top of the transmission.
This is going to be harder for you due to the fact that you most likely do not have the computer diagnostic tools to properly diagnose the problem. There is good news though. In my experience with this in nissans about 95 percent of the time it's a bad speed sensor. As long as you have a good ohm meter you will be able to test it yourself. If it tests out good then you may need to take it in unless you are able to track down the wring short or problem which in worse case it's the ECM. The P0720 is basically telling the computer to let you know there is a problem and tells the ECM to turn on the MIL (engine light, malfunction indicator light). The P1574 like I said in most cases it's the speed sensor. Below I took some snapshots out of the factory service manual for your vehicle. two of them are a description of the DTC's (diagnostic trouble codes) you pulled from the ECM. The other snapshot is how to test the speed sensor without any real fancy equipment to where you are able to just use an ohm meter to check resistance. If the ranges are off then you need to replace the sensor which if I was a betting man would say that's your problem but always test before you start spending money for nothing.
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For error code p0720, this is the sensor, that has to be replaced:---
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remove driver side splash guard to access. held in place by 2 screws and a 10mm. Sensor is held down by 10mm.
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Top part of sensor:--
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old on the left, new on the right. old sensor was lightly covered w/ fine metal shavings.
