Possible Electrical Issue Causing P0420 and P0430

Hey all, I've been dealing with a check engine light for probably the last year and a half. It's been slightly on and off at times. Code readers say that it is P0420 and P0430. I've gone to a few mechanics and the first time we went through all the 02 sensors and all of them checked out. The truck only has about 88000 miles on it (had much less when the issue first started) and doesn't make much sense for the cats to be bad. I had a mechanic tell me to run seafoam through the vacuum hose to clean the cats, told me that if they were really dirty it would throw those codes and the seafoam would produce a lot of smoke. I ran through the process and almost no smoke came out of my exhaust. It also didn't fix the CEL like he thought it would. This leads to me thinking there is a possible electrical/computer issue that is causing the codes. The issue started from a loose add-a-fuse that was tied into the INJ fuse location under the hood. I did the raptor light mod and apparently the fuse was not pressed all the way down, it popped loose one day while driving and sent the truck through a whole lot of fits. Started flashing all sorts of warning lights and messages on the dash and shut the truck completely off while driving. I was on the freeway at the time and pulled over, turned the truck off and back on and it was like nothing had happened for a few miles and then it did it again, and again, and again a few more times until I could get off an exit. I found the loose fuse, plugged it all the way in and the truck has ran fine ever since, but the CEL remains on. I'm stumped on what to do but I have to register the truck which requires it to pass emissions and it won't do that with the CEL on.

 

Basically you need an educated mechanic to test the cats. It's very unlikely electrical.

There's two ways to test it.

1: Sniffer/exhaust meter.

2: Watch o2 sensor voltages and trigger a fuel trim change.

So you watch the upstream sensor before the cat, then trigger a big change, like a vacuum leak. Then watch the downstream o2 sensor after the cat to see how long it takes to react. A bad cat the downstream will virtually mimic the upstream. A good cat will have a 1 second or more delay.



Most bad cat's you can smell, it will smell "rich" or like unburnt fuel and stinky like an old car.

Toyota advises lately to replace the upstream A/F sensor prior to changing the cat, but I'm not sold. If there's no exhaust leaks, and the sensors are reading, its the cat. There's probably 30 codes for the o2/af sensors so its testing them all the time.

Cat's are mechanical/chemical, they are simply monitored, but not controlled electronically.

To me it sounds like the cats are pooched but I'd have them tested by someone that won't sell you snake oil.

 

You tapped into an injector circuit to power up some lights?

 

Yeah in hindsight I'm not sure why I didn't think twice about it. Found some thread on here or YouTube video that said that's what fuse they chose so I just followed suit.

 

When first looking at it with a mechanic we did look at the voltage readings but I don't know if he tried any triggers. As far as smell goes I haven't sensed even the slightest smell from it. Wouldn't there also be a significant drop in performance if bad cats was the case? I haven't seen any noticeable change to my MPG's. At times the CEL light will also just kick off by itself. Would that be possible with pooched cats?

 

Have you relocated this?, get that off injector circuit.

 

Yeah that was done long ago haha

 

Did you clear codes after doing that?

 

I would get it to a qualified tech. Nothing against your mom n pop places, but in this case it doesn't sound like they saved you any money.