dtc codes questions p0422 and more
 

i started a thread about this before but it is buried far enough down so i will ask again. i have these codes p0422 p0457 p0456 p0441
p0420 cat issues in this order
p0457 large leak
p0456 small leak
p0441 purge valve

ok in doing some research they say fist the first code and that may take care of the rest. i don't think the first code is the start of the issues. 457 and 456 are leaks in the evap system that we have talked about and some on 420. but not 441 yet. so i'm wondering if 420 is related to the 441 code? 441 is something to do with the purge valve or a blockage. might be a break in the line as well but then that will be in the 457 and 456 codes. but what might be causing the 420 cat code? can the other codes cause the cat to go wild? i did run a test on the cat before when that code came up but it was by itself now the 441 purge valve is a new one. any ideas? or do i start with the 457 and 456 and get rid of them and then see if the 441 and 420 go away by themselves?

when i ran the 420 tests before the front 02 sensor was going up and down like it should but so was the rear 02 sensor some sid normal but in some research they said the rear 02 should hold somewhat steady at around the center of the scale. they where saying if the rear sensor is going wild then the front sensor will also trying to keep up. my girl is telling me she is getting poor mileage and that may be what is making the cat go wild? and the 420 code? thanks

Spend a few dollars at a good Independent auto center and have a "smoke test" done to find leaks. It will save TIME and less head scratching(and pulling out hair), than to try and Electrically figure out the problem. EVAP leaks will cause O2 readings to go wacky, such as the P0420 code you are getting. Once outright leaks are found and repaired, go on from there with any other concerns.

rebel59 i just built a smoke tester and will do this in a few weeks when i can get my hands on the car. just asking if anyone had this type of situation and if the 420 code can be caused by the other codes. i believe the purge valve is failing. i had the car in the garage a few weeks ago and i did a vacuum test on the lines and they passed. i could not test the nvld or the purge valves at that time. and i was able to vacuum a test on the lines back to the tank but not the tank. in a few weeks i will do the smoke test on the complete system that will tell me more. thanks much

Sounds good, BUT hope you also have a hoist to put the car on and be able to easily pinpoint any potential smoke leaks!

i have jack stands and can get under the car easy to look for smoke. i built the tester and used it on my cobalt to find leaks as i was smelling gas and was curious if it was the evap system or something else. that turned out to be a rusted gas line at the fuel filter. but the smoke tester worked fine. and i do have a hoist as well but not yet available for working on cars as my antiques are using it. weather not good enough yet to move them off the rack.

when i get the car in a few weeks i will do a complete test and find the faults and fix it, then see if the cat code returns. i'm leaning towards that fault being caused by the evap not working and causing the rest. we will see then. thanks for the help.

well it looks like i get the pacifica this weekend and if so i get to dig into the evap issue we have been talking about. just in case i got a new nvld for it, i will install it even if the old one turns out to be good so i should not have to lift the car for that issue again providing that part is a good one. i will come back here after i'm done and post any and all issues i found. i'm going to start with the smoke test just to see if i can find anything before i tear it all apart, i may get lucky and find the issue/s and then have a good starting point. but the nvld will still get changed out for good measure.

one thing i did find out is the p0420 code could be caused from oil consumption. there is a lot of talk in some forums about that code and using oil from about 2008. and the code was gone for a long time, then my girl needed some oil to refill the crankcase and got some mobile one. that is real thin oil and then she said the engine light returned, i scanned it and got the p0420 so these may be related with the oil coating the cat causing the code.

if after doing this work the code returns i'm going to try the lacquer thinner treatment and see if that cleans out the cat. if not then i will take it off and clean it and if that fails then the extend the o2 out of the exhaust flow.

GOOD LUCK to you! hope you find an easy to replace split EVAP HOSE as the culprit. Had that happen 3 times on my last T&C. The last leak was hose connection leak at the NVLD unit!

i hope i find an easy one too. i'm hoping the smoke tester will show me any issues like that. if not i'm taking the complete system out of the car and testing each hose and part separately i will find it if it is there. even if i have to put the vacuum tester in each hose and run a vacuum test i will find it. or i will just replace everything new and then it will be gone. but for the sake of money i hoping i find a loose or split line or fitting somewhere.

thanks for the encouragement.

ok this is what i found so far! i did the smoke test and no smoke anywhere. so i took off the nvld and plugged that hose so i could put more pressure on the system. i put 2 psi on the system with the nvld out of the system and the hose plugged and after about 15 minutes and still no smoke i took off the gas cap to fe the smoke to that point anyway. then after 15 minutes i took out the rear passenger seat and opened the cover to the fuel pump and no smoke. that is one trouble point in these cars also. then i took off the problematic fitting that goes to the other pump and i got the pressure out of the tank and then the smoke started. so i put the fitting back on. so my system must be able to hold pressure or vacuum.

then i tested the old nvld and i got nothing when measuring ohms across any pin. the new one i got
pin 1-2 pl to .001 when blowing or sucking
pin 1-3 .001 blowing or sucking
pin 2-3 .9 to .001 blowing or sucking.

that is telling me the new nvld is doing something the old nvld was not doing, so i put it back together and cleared the codes and now i have to fill the tank so the evap will run the nest test tomorrow or tuesday.

if i get the same codes then i have to drain the tanks and take off the tank and check each hose but if it was holding pressure and now smoke i think the nvld may have been the issue. when smoking it i did get smoke out of the vent but that maybe a normal thing if i had more pressure than the nvld was able to hold back or a normal venting process thru the canister filter.

i took the old nvld apart and ohming out the pins in the switch i got nothing but if i shorted the connection just in front of the switching then i got a reading. there is a switch and what looks like a pressure type switch hidden under the lever. the lever hits that pressure type switch and the other switch is driven by the smaller diaphragm so for now i have to wait for a cold soak. i will post any changes thanks

Sounds like you may have gotten the fix. I had replaced the NVLD on my van, but found the hose connection to it being bad during the change. But since it was "in work" decided to put the new one in anyway!