P0420 Code

charlie2 · Mar 26, 2023

Alright, I'm back again but with a new code this time. I own a 2018 RAM1500 EcoDiesel and this time I have a P0420 that the engine threw this afternoon after I drove after a while. The code read "Catalyst System Efficiency Below Threshold." The truck runs great. I see no difference in MPG, and performance is great! I just want to know if anyone else experience this code and what was done in order to remove it. I want to try everything before going to dealer and having them fix it. Everyone keeps recommending a catalytic converter cleaner but how do I know which one will do the job? Any brand recommendations? Any advice is recommended!!

Also, is it safe for me to continue driving the truck with this code on?
Thanks in advance!

Bounty Hunter · Mar 27, 2023

Do not listen to anyone that recommended a converter cleaner LMAO.

Likely a clogged DEF injector. Remove the injector, inspect it, and steam clean it.

charlie2 · Mar 27, 2023

Bounty Hunter said:
Do not listen to anyone that recommended a converter cleaner LMAO.

Likely a clogged DEF injector. Remove the injector, inspect it, and steam clean it.

Will definitely try this and let you know if this worked. Truck is running great right now even with the code, so I am hoping it's just a faulty sensor or the injector like you stated.

Brokedownbutgood · Mar 27, 2023

That code means your not getting the expected temps during a regen. Its very possible you have a egt sensor not reading correctly or your doc is getting face plugged. An exhaust leak could cause it as well. Has your truck ever had a egr failure?

charlie2 · Mar 27, 2023

He was actually in the dealer about a year ago because the truck had a P0299 code, I think. I can't remember what code it was, but I know it was the EGR cooler that needed to be replaced. Truck was in the dealer for about 1 week and I picked it up and it was running well once again. I did not experience any issue after that.

RamCares · Mar 27, 2023

We regret to see that you're having these concerns with your truck. If you do decide to have this looked at by your dealer, let us know. We're available via direct message and can help with this process.

Callie
Ram Cares

Kazimodo · Mar 29, 2023

there is a pdf on step by step DEF injector removal , I got it somewhere on the site .

Jmo · Oct 19, 2023

What was the fix you found for the P0420 code. I've been deleting the code but it comes back every 100 miles or so.

amcockriel · Nov 21, 2024

I’m wondering the same. I just got this CEL code too and have turned it off a couple times but comes back every now and then. No issues with MPG or anything else. I have a 2019 Eco.

ekalb89 · Mar 27, 2025

Anyone find resolution on this code? Cleaned my injector which was clogged. I was hopeful, but it keeps coming back.

P0420 Code

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