Hey guys I had this problem over the weekend and after searching on forum info was poor at best. Here is what I have found. This sensor is used by all the dodge cars that use this platform and this seems to be a common problem. The process is pretty simple.
First off this code will only come up when you are traveling at 50mph or higher and engine coolant is 86F and above.
The 0551 code will only come on for two reasons. bad sensor or something is actually wrong with the power steering system.
In my case, I wasn't having any indications that i was having a real problem. After reading in the service manual, one of the jobs of this sensor is to maintain idle when steering (like maneuvering in a parking lot) it tells the pcm to up the idle so the car doesn't bog down. Well I never thought anything of it but my car would bog down if i was setting still and moving the steering wheel. I replaced the pressure switch and it fixed it.
The pressure switch can be bought from Autozone for about 28 bucks (part#PS399). I called napa and O'riely and they do not have it. You can also get it from your dealer or from RockAuto Parts Catalog
So you will need the switch, power steering fluid, 7/8" deep well socket, extension longer then 8" long, jack, jack stands, something to catch the fluid, and some rags.
- Jack the car up on the driver side, enough for you to get under it
- crawl under behind the front tire and look about the crossmember you will see the pump and a sensor coming straight out toward you(see picture below)
- unplug sensor(its bitch due to the lack of space)
- get your oil catching container ready and use your socket wrench to unscrew the sensor(the deep socket allows you to go over the connector)
- let as much fluid drain as you want. Make sure the old rubber o ring came off with the old sensor and install new sensor BY HAND.
- Tighten new sensor but be careful not to over tighten to damage the sensor or worse the pump.
- Take your time and clean all the old fluid off car. the cleaner you get it will help you know if you have a leak
- reconnect the sensor
- lower the car back off the jacks and fill the power steering pump back up.
- start the car and go from lock to lock on the wheel. Turn off motor and recheck fluid level.
- After the fluid has reached the full mark let the car run and look under to see if you seeing anything leaking.
- I turned the car off and rejacked the car up and checked to be sure.
- reset the code and take a 30 minute highway cruise to see if the problem is fixed.
Here is a picture of the sensor from the service manual
Here is the two pages from the service manual for deeper trouble shooting of the switch and wiring and a little more details of what I just went over.