Just got a P0420 a couple days after putting some additech in my tank. I know this is a cat problem - but I don’t smell the telltale signs of cat failure and the truck is driving, shifting and idling just A-OK. Is it possible it’s just the damn sensors? I went to a dealership here where I live and they couldn’t look at it. But the service manager cleared the code and said what I said “no smell, no engine issues - probably not the cat but if the error comes back make an appointment and we’ll check it out”.

anyone provide some additional thoughts on this? I’m not gonna even bother to ask if CataClean works. AutoZone already tried to sell me that crap. And that’s a big nope from me.

 

Did you mean P0420?

P0240 is Turbocharger/Supercharger Boost Sensor-2 Circuit Range/Performance.

 

yes. Sorry 420. It’s been a long *** day.

 

The possible causes for a P0420 are:

• Damaged heated oxygen sensor (HO2S)
• Exhaust leaks
• Damaged exhaust manifold
• Damaged catalytic converter
• Oil contamination
• Cylinder misfiring
• Downstream HO2S wires incorrectly connected
• Damaged exhaust system pipe
• Damaged muffler and tailpipe assembly
• Evaporative emission (EVAP) purge valve stuck open
• Leaking fuel injector
• Oil contamination of the catalyst
• Damaged turbocharger
• Base engine concerns

I can't comment on the additive you used. Never used it or even seen it available here.

 

Thanks! Additech is just a gas detergent. It’s the stuff Chevron puts in their gas normally (I think). But we don’t have chevron where I am. I live in a real small *** town in Texas so there’s not a lot of options mechanic wise. I’m going to ask one of the two guys in town if they can look at the o2 sensors.

 

P420 is for Bank-1 which is the passenger side so they only need to look on that side.

 

Think!
Why would you think a gas additive will make a code 420 clear? Does it say on the Label it has a use for that fault?
The Cat is no longer cleaning the exhaust well enough as detected by the REAR sensor.
That is why there is a rear Sensor.in the middle of the Cat case.
There may be a reason the Cat is failing, as Merc listed above.
Good luck.

 

OP stated the code appeared after they used the additive...

 

I think he was confused because I mentioned two different additives. And yeah, I agree. I doubt anything you put in the tank solves problems. Although I can imagine them causing problems. I’m taking my truck in to a guy in Corpus Cristi Monday and we’ll see what’s up. I think it’s an o2 sensor though. I smell no eggs, gas mileage is actually stellar for a 2017 with 100k miles on it - I’m hitting 20-21 on the highways here in Texas.

There’s no odd acceleration or rough idle. Or really any issues with the vehicle of any kind and I changed all the sparks, boots and coil packs myself with OE stuff at 88k. And I change oil and filter every 4500 miles with OE filter and penzoil platinum full syn.