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On the DI engines the cat code P0420 is very likely to be caused by failed fuel injectors, in my experience.
One or two injectors squirting too rich can and will cause a cat failure code, and it can set that cat code without setting misfire or injector balance (trim) codes even when the injectors are the root cause.
Most of the time this requires replacing the injectors, then let the car go so we can wait and see if the cat code returns later.
The only scanner I know that can run the fuel injector self tests is the dealers HDS scanner
On the DI engines the cat code P0420 is very likely to be caused by failed fuel injectors, in my experience.
One or two injectors squirting too rich can and will cause a cat failure code, and it can set that cat code without setting misfire or injector balance (trim) codes even when the injectors are the root cause.
Most of the time this requires replacing the injectors, then let the car go so we can wait and see if the cat code returns later.
The only scanner I know that can run the fuel injector self tests is the dealers HDS scanner
Well, I reset the code and it hasn’t come back yet.
Besides using the HDS scanner, are there any other symptoms I should be on the lookout for that would indicate bad injectors?
On the DI engines the cat code P0420 is very likely to be caused by failed fuel injectors, in my experience.
One or two injectors squirting too rich can and will cause a cat failure code, and it can set that cat code without setting misfire or injector balance (trim) codes even when the injectors are the root cause.
Most of the time this requires replacing the injectors, then let the car go so we can wait and see if the cat code returns later.
The only scanner I know that can run the fuel injector self tests is the dealers HDS scanner
ezone thanks for the additional info! My experience has always been with non-DI p0420 codes. Usually bad coil or old plugs and the person waits to darn long and burns the cat up. DI wise I’ve had to deal with carbon buildup but never went long enough to get a p0420 code. Overfuelling makes a lot of sense. Thanks again!
i know its an old Post BUT im have this issue, and you guys are the closest of my diag all around the internet
So here we go, I'm a mechanic for lil bit less then 20years, just buy a 280K km fit at the scrap yard xDDD and i had couple issue, including this one (p0420), cleared, and come back 20-30km later , 2time. so i found couple solution so far, found the TSB for 2015 (all) and 2016 (some) : TSB https://static.nhtsa.gov/odi/tsbs/20...33022-9999.pdf
now im here just to say that i have a Autel Scan tool at work and i got there as soon as i found this TSB to check if i have the A/F Test function, and i have it, run the test 2 time :
so here, first time Cyl 4 too rich (probably leaking in cylinder and missfire was not that high rate has cyl 1 . then Cyl 2 came too at the second test.
So my question is: anyone have saved their injector with a Cleaner of some sort, OR Install a O2 sensor spacer to fix the trouble :
So yeah, if ur mecanic have an autel, he can run this test for you to see if its a bad injector.
I had a P0420. Fixed it by running a tank of Chevron Premium AND cleaning the air filter.....it's a K+N cleanable......
Went back to cheap gas and got the code again.......BUT, I'd already passed Smog after I fixed it, so now I'm thinking of using an EDM auto o2 sensor spacer adjustable on the downstream O2 sensor to see if the engine light will clear........
it might work to clear it....which sounds like all you need....but it might be a bad cat caused by bad fuel injectors...like ezone alludes to..on a 2015 only
Run fuel injector balance test, I think that's what you did there on your scanner. I didn't even bother "cleaning" them. You can if you have the time to fudge around with a backup beater car, taking off intake manifold, putting in back on then rescan and drive to test constantly.
The failure of modern direction injection car = direct injection fuel injectors and crusted valves. $1000 that can be used on fuel or other maintenance parts but used to replace injectors instead to get 33mpg+
