Dodge Repair Questions? Ask a Mechanic for Answers ASAP
the p0420 means the cats are junk and could easily be causing the "rls" especially if they (or just 1) are beginning to clog, the p0171 is bank 1 system lean bank 1 is on the DRIVERS side which can also cause the truck to run poorly, a lean code can be caused by a clogged cat OR a vacuum leak at the drivers side OR if you used a BOSCH or any universal o2 sensor, for some reason BOSCH sensors throw codes and never work properly the OEM manufacturer for our o2 sensors is NGK and they work ok.
to see if the cats are clogging remove and set aside the o2 sensors ABOVE the cat this will allow the exhaust a clear (but loud) path to escape if the truck now runs ok the exhaust is clogged and the cats need replacing.
other causes of a lean code is low fuel pressure (55 psi UNDER ALL LOADS, that means you may need to drive the truck under a load with a fuel pressure gauge safely secured where you can read it)
overdrive has the highest load on the engine so if anything fuel related is weak well that's where it will show up, when were the spark plugs last changed?
due every 30k on this engine and absolutely NOTHING but the oem NGK or champ's COPPER CORE that came out, when is the p0171 setting? does it set right away or after a drive, bucking is rarely a trans problem UNLESS it is shifting in and out of overdrive, do you have a good scan tool? you will need one to see what is going on, with a p0420 the firt thing is eliminate any clogged or partially clogged cats GOTTA start with the obvious and you stated the engine computer is throwing cat codes ad a lean code you need to resolve these FIRST then see how the truck runs, it's how a proper diagnosis is started.
map sensors are super rare modern sensors last a while and the last map that I had fail was on a hemi some years ago, o2 sensors yup they have a life span of 100k and universal ones don't work, bosch are junk lately with sensors I head to NAPA or OEM too many times chasing my tail on a cheap part, crank sensors fail too BUT WILL set a code, OBD2 rules state every part that can effect emissions HAS to be monitored for 1) being properly installed, and 2) working properly so we now have literally hundreds of codes that can set
the exact plug that came from the factory SHOULD BE CAMPION RCMCC4 don't bother with platinum or any other plug they never work right and usually cause misfires.
as for the o2 sure pull the drivers upstream o2 and see how she runs but since these are cats that come as a package of all 3 (from the factory that is ) you get all 3 general rule is if one is dead the others can't be far behind
a decent scan tool from OTC on amaon is around 2 bills but you do need to know what the data you are seeing means
the third one is for NOX the 2 upper ones are for CO and HC my state of CT we are a California emissions state and the fine is huge to remove the third cat, I don't know about your state but if you have adopted California emissions and have an inspection they will catch it and either fine you and fail the truck or fail the truck and not report it up to the inspector, we are watched on the inspection lanes (all independent shops with cameras linked to dmv) and they randomly send rigged vehicles to test and see who is cheating
btw since your truck is a cali emissions truck you need to use cali emissions cats or you will throw codes for bad cats still, cali emissions programming is much stricter than federal and NO once a vehicle is built to cali spec it cannot be downgraded that's a federal mandate, and 99% of vehicles built now are California emissions anyway
I would try NAPA or anyone that sells WALKER exhaust parts the OEM number is ***** and NAPA can cross that over, but they don't show a cat to fit your truck in MY area your store will very likely have a huge catalog and can get one and rock auto shows one as well here is a link to them, they are out there but may take a bit of research on you part
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