Can MMo cause p0420 code? Got one using MMO

[mk378]

P0420 almost always means the cat is bad. This can be investigated further by scanning live data. Or if you have to do a tailpipe smog test and it fails, then you know.

Remove the question of if additives are harmful by not using any. They aren't helping anything.

 

[kschachn]

I used Lucas ucl, big gallon and half container all spring,summer,fall. No hi ssues.one tank mmo...set off the upstream sensor /CAT. It is an aftermarket cat,I had a new exhaust system put on 3_4 years ago. Old cat was shot. Mechanic showed me old one..the comb in it,was completely broken ,cracked,holes in hi t from pieces missing,and rust galore. I do know aftermarket ones are nowhere near the quality of factory..won't last as long I have out at least 37,000 miles on it since installed.
Made me think.maybe the cat is on way out and not the mmo?I believe the cat,new one installed was a bosal.
I question it,because they did not install new muffler tailpipe.though it was on receipt.the clamps.were not new...I looked under it after.mechanics often do things like this. Why I try to do mY lol an stuff..so not ripped off.

Just interested, what’s wrong with your engine that you’re trying to fix with Lucas and MMO?

 

[PimTac]

Just interested, what’s wrong with your engine that you’re trying to fix with Lucas and MMO?

It’s a LeSabre. There seems to be a few members here with problems on this model of car.

 

[Kurtatron]

P0420? Maybe cut back on the MJ?

 

[ziggy]

Well,I went avoid 175 miles,no code.put 8 odd ammo in 13 gallons( I'm assuming their 4-5 gallons still in tank,though needle was halfway through orange empty indicator on fuel level on dash). Used citgo 87,triclean. Drove 40-50 miles now,maybe 60,code came back.
Its a new AC Delco upstream I hug ad put in months and months ago.should only have 10-20,000 miles on it.
I did note,in car tonigjtt,idling few minutes at store,a sweet smoky smell.that tells me exhaust leak.windows up too..you could smell it.somewhat a exhaust fuel smell.
I USD Lucas ucl..not onecode. Don't think my exhaust system likes MMO.
I'm funny discontinue mom next tank.use Lucas ,see what happens.
I have a code reader,tells you ect.bought it walmart. You can see live data...02 is checked green.but engine diagram is red x...its showing me,02 sensors are both green checked.

So,either cat is bad then,or mmo n car don't Like eachother.

 

[CourierDriver]

After many years here , I have come to the conclusion that all of us are experts on car repairs, and medicines and how to cure all sorts of ills....lol, so this MMO thing is nothing new...we always blame the last thing we do that destroyed the system ......MMO has been around longer then most of us have been on the planet. It is a mild cleaner, it usually does not dissolve co2 sensors, but it will clean your rifles and pistols, of course I'm correct because I say so...enjoy your day and don't forget to wash your hands,,lol

 

[PimTac]

Well,I went avoid 175 miles,no code.put 8 odd ammo in 13 gallons( I'm assuming their 4-5 gallons still in tank,though needle was halfway through orange empty indicator on fuel level on dash). Used citgo 87,triclean. Drove 40-50 miles now,maybe 60,code came back.
Its a new AC Delco upstream I hug ad put in months and months ago.should only have 10-20,000 miles on it.
I did note,in car tonigjtt,idling few minutes at store,a sweet smoky smell.that tells me exhaust leak.windows up too..you could smell it.somewhat a exhaust fuel smell.
I USD Lucas ucl..not onecode. Don't think my exhaust system likes MMO.
I'm funny discontinue mom next tank.use Lucas ,see what happens.
I have a code reader,tells you ect.bought it walmart. You can see live data...02 is checked green.but engine diagram is red x...its showing me,02 sensors are both green checked.

So,either cat is bad then,or mmo n car don't Like eachother.

We are being played.