P0441 is for: “Evaporative Emission System Incorrect Purge Flow.”

P0420 is for: “Catalyst System Efficiency Below Threshold (Bank 1) DTC Severity 2 of 3 Repair Immediately If Drivability Issues.”

For some background info - MAF Sensor, Intake Filter and Catalytic Converter have ALL been replaced with brand-new OEM parts (minus the air-filter which is K&N Aftermarket from Walmart; not actually entirely sure it’s considered ‘Aftermarket’ since I believe it claimed to be ‘OEM-equal’ or however it’s phrased on the packaging — I threw it away already and don’t remember exactly what it said or the part #, although I could find out fairly easily by checking w/ Walmart Auto Service; I believe it was 2031 or 22031 or something along those lines, but it was a perfect & easy installation/fit and the MPG improved rather markedly from ~18.6mpg to ~20.3mpg, after resetting the mpg reading through holding down the “info” button on the time/distance-mileage-measured reading, not the ‘real-time’ reading, with about 120 miles driven since.

So, I’m thinking it’s the O2 sensor(s), but not entirely sure and wondering if anyone has had the same problems (especially after same/similar prior fixes were made, such as the filter, cat & MAF sensor - but I suppose that may not necessarily matter, just positinf the possibility..)

If it IS the sensor(s), how many are there in each location (which - I believe - are the engine block & cat..?) and if it’s not (or *may* not be) then what other possibilities could it be?

I appreciate any help that can be offered and thank you for any suggestions in advance. Pics included.

P0441

P0420

 

I would suggest take care of the purge flow issue first [should be easier to locate and fix].

The other issue is more complex as it in a closed loop [intake, burn, exhaust (unburnt)].

Salim

 

Well I guess that’s kinda what I’m asking about. From just some cursory searching, I’ve been led to believe that that could be due to the O2 sensors, but I’m not at all confident w that answer, so just wondering what I would need to be checkin first?

As for the other issue being ‘more complex’ are you saying it’s not just the system reading potential catalytic converter fouling due to the purge issue and it wouldn’t be fixed by fixing the first code?

 

Also - the code specifies “Repair Immediately if drivability issues,” but I’ve had quite the contrary since replacing the cat, MAF and intake filter. The car has gone up, in total, from about 13mpg when I first fixed the CAT (plus 2 misfires which I’m sure were a major component - but I’m not worried about those at all being part of the equation really cause I did a full spark plug and coil pack swap just to be safe, as I just recently got the car and it’s got 220k miles, so like… yeah.. was probably due for all new stuff for sure.) and now it’s around 20.3mpg consistently which is pretty good for this car being a ‘99 AWD w/ 220k miles, I think.

And now the car is running perfectly fine, switching gears fine, accelerating fine, idling fine, no strange smells or leaks.. only thing is some crazy squeaking for about 10 seconds on really cold starts (gets down to around 8° sometimes where I’m at) but I assume that’s just the belts and I’ll get to that eventually.

Mainly just want to make sure there’s nothing wrong with the system I just most recently worked on and spent a good amount of $ on, so as to avoid undoing any of the ‘progress’ I’ve made - like foulin up a new cat.