2001 Dodge Neon Fault Codes on 2001 Dodge Neon: P1684 &

Hello.
My check engine light came on this morning and I took it to the Auto Parts store where they said the code came up for "Power Steering Sensor/Wiring"

I figured out how to look up the codes myself and got two:
P1684 *The battery has been disconnected within the last 50 starts (I was told this is a typical fault code and doesnt need any followup)
P0551 *Power Steering Performance Rational?? I think?? I'm not sure what this code means and what I need to do in order to repair it.

Any advice would be greatly appreciated.

Thanks,
Christy