2006 Pathfinder P0420 & P0430 Code Question

[CiK]

Sorry for the long story. I don't want to miss any detail as I ask for help.

In September 2018 I was driving from Indiana to Wyoming. Indiana elevation of 1,100ft, Wyoming elevation of 10,000ft. In Nebraska (4,000ft elevation) and on the interstate, my 2006 Pathfinder started chugging like the gas tank was empty and stalled at cruising speed. I had a full tank of gas. After pulling off the side of the highway, I turned the key off and restarted the engine. The Pathfinder started up ok but the Check Engine Light came on immediately. I tried a few of the things I read to reset the ECM, but the Check Engine Light always came back on immediately after starting the Pathfinder back up.

I decided to not bother with it until recently because the fuel milage decrease is annoying me (18mpg to 15mpg even when I got home to Indiana). I recently changed out the rear O2 sensors on Bank 1 and Bank 2. While I can get the Check Engine Light to clear and not come on immediately, it does come back on at highway speed with the same P0420 and P0430 codes.

For those with more experience, should I be looking at changing A/F sensors on Bank 1 and Bank 2 next? Can catalytic converters fail instantaneously like that and they be the root cause?

Thanks for the help. 2006 Nissan Pathfinder with 145,000 miles on it.

Tony

[CRC11007]

I ended up with the same codes, and replaced both primary cats and upstream O2 sensors. But it never caused any drivability issues like you described.
My engine did die a couple times while driving, similar to what you described. I replaced both camshaft position sensors and the crankshaft position sensor (using genuine Nissan dealer replacement parts) and it hasn’t died since. That’s been over three years ago.

[smj999smj]

If the engine was "chugging" then likely it was misfiring at the time. Misfiring can cause unburned fuel to be sent to the upstream converters, which can damage them. It's not uncommon to hear from people whom have had catalyst efficiency codes trigger after replacing a bad cam position sensor, or sensors. Cam position and crank position sensors can sometimes fail, cause drivability issues and not trigger a trouble code or turn on the CEL. It's impossible to say if that's what happened to your vehicle, but it is entirely possible. If you haven't already done so, it might be worth checking for stored codes even if the CEL isn't illuminated. If you do end up replacing the upstream converters, it should be noted that most companies require replacement of the upstream oxygen (or air/fuel ratio) sensors with converter replacement to enforce the warranty.

[CiK]

If you do end up replacing the upstream converters, it should be noted that most companies require replacement of the upstream oxygen (or air/fuel ratio) sensors with converter replacement to enforce the warranty.

I was thinking about just changing the upstream A/F sensors to see if they make a difference by themselves, but I bought an OBDII scan tool because I nerd out and like to understand things. I don't like to use blanket statements, but I have read that if the downstream sensors are not charting with the upstream sensors then the catalytic converters are most likely shot. Attaching images of what I am seeing after the car got up to temperature.

Any thoughts?

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