I just bought a used 2001 Durango 4.7 4x4 this week. I am a novice so please explain in terms I will understand. My husband understands more and can do the work himself, but we end up doing more than necessary until we figure things out.

The check engine light is on and saw P0420 and P0551.

I bought a power steering pressure switch for my husband to replace, am I assuming correctly that this will correct the P0551 code?

Now to the P0420 code. Does this mean I need to replace the catalytic converter or I saw on other forums cat o2 sensors which I am not sure what they mean. There is white smoke coming out the back that smells like when I had an oil change and they spilled oil on the engine and it smelled bad until it finally burned off. Nothing makes it smoke more or less.

Thank you for any detailed help.

 

the 0420 is most likely the post cat o2 sensor gone bad, but if that doesnt fix it then id look at the cat.

the new power steering switch should fix the 0551 code, however i would check the harness for fluid while im in there, iirc the o2 sensors and the power steering sensor share a loom in the harness somewhere and when the pressure switch leaks it shorts out o2 sensors.

 

I assume post cat is the downstream O2 sensor? And looking in Autozone they have upstream, downstream and also both of those in Left and Right choices. Do I go with just downstream and ignore left and right?

Thanks.

 

post cat is the same as downstream, and the right and left only applies to vehicles with california emissions on it, if you dont have a CA emissions truck you dont need to worry about it (crawl underneath the truck and check for sensors on the exhaust pipe before the Y pipe, chances are you dont have any up there and its down farther behind the main CAT.

 

My 2¢. I'd swap the cat. The sensors are designed to tell you a part that eventually goes bad 100% of the time as miles go by has indeed gone bad. Just swapping sensors is like putting a bandaid on a melanoma spot.

 

however the combination of codes leads to the likely outcome of a short in the sensor wire, throwing a false code, and sensors are much cheaper than a new cat, so a replacement of the sensors and a cleaning of the harness is a much more financially sound place to start than replacing the CAT.

 

So do I need to replace both sensors or just the downstream? Also I live in SC so we don't have emissions control here, after replacing the sensor or sensors and if it turns out to be the cat converter, is there a problem by just running straight pipe other than sound?

 

My 2¢ again... I actually meant swap out both the cat AND the O2 sensors, just crawl under once. To me, cheap isn't the highest priority when talking about a once every 100,000 miles maint. Don't get lowest price O2's either. Get what has the highest rating for working the first time.

 

i would only replace the downstream sensor, and i second buying a decent on and not cheaping out on the o2 sensor.

the only problem functionally with running straight pip instead of a cat is that you will have the CEL on, if you can deal with that then its fine.

however if your car is still running right and the CEL doesnt bother you then youc ould even leave the CAT in place until it starts causing more issues (it might not ever be a problem except for the CEL)

 

You could always purchase a high flow cat (not allowed in cali) for cheap and not get a cell light. I put a MagnaFlow high flow and works great (you can find them cheaper ya don't need a MagnaFlow ).