First off, I know nothing about cars... except how to hit the gas peddle. However, I need help. My car needs to be inspected by the end of the month, and my engine light is on. My boyfriend can fix whatever is wrong, I just need to know what the codes mean. The car is a 2002 neon, automatic. I have gotten the CEL codes p0551 and p1684. I hope it is a cheap and easy fix, because not only is it due at the end of the month but I'm also due to have a baby at the end of the month and money is rather tight. I've googled these codes and the p1684 says battery a lot...I know there is a lot of corrosion on my battery, and a few months ago my boyfriend had cleaned it but it came back. Thanks in advance for any input.

 

The 1684 should be the power steering pressure switch, those are the same 2 codes for my car ATM.

 

p0551 - Power steering Pressure Sensor Circuit Range/Performance
and
p1684 - Battery Disconnected within last 50 starts

 

If you are getting P1684 and haven't disconnected the battery, but have a lot of corrosion as you say, it could be losing ground causing the code. That code will not trip the CEL though. Clean the battery terminals and posts and either buy the anti-corrosion spray or coat the post and the terminals with some petroleum jelly to stop the corrosion.

P0551 is likely either some bad wiring or the switch itself. Check the wiring first to make sure it is good. If the wiring is bad and you replace the good switch, you'll still have the problem.