After five successful years using Chevron Techron to clear the P0420 code, it seems my luck has run out. Even after two doses (20 oz in a full tank and 12 oz in a half tank), the Check Engine Light (CEL) returned quickly. The first time, the CEL reappeared after 250 miles, while the second time, it took only 10 miles. A battery disconnect (overnight for the first attempt and a couple of hours for the second) didn’t seem to make a difference.
Resigned to finding a new solution, I purchased a Dorman spark plug non-fouler (42002) for $4.00 at AutoZone. I drilled a 1/2 inch hole in one of the non-foulers, attached the two together, and installed them onto the catalytic converter. Finally, I carefully screwed in the O2 sensor, ensuring the wiring remained untwisted and stress-free. Applying anti-seize to all threads helped prevent future issues. Fortunately, the Vegas weather made removing the O2 sensor easy with a standard 7/8 inch open-end wrench; no special O2 sensor socket was necessary. After erasing the code, I’ve driven 20 miles without the CEL returning.
The non-fouler positions the O2 sensor tip approximately one inch away from the exhaust stream. This increased distance should prevent premature catalytic converter failure triggered by Honda’s sensitive parameters. It might even be far enough to prevent a CEL even if the catalytic converter performance dips below the legal limit. I’ll find out in eight months during my annual smog check. I’m considering removing the non-fouler before then, when the summer fuel blend returns, to test if the P0420 code reappears.
In my Vegas smog check experiences, the inspector hasn’t visually examined the O2 sensor. However, the extended length due to the non-fouler would be noticeable upon inspection. I’m unsure about the legality of this fix in Nevada, but I’ll know by August if it passes the smog test. I don’t plan on volunteering this information to the inspector. I’ll keep you updated on the results.
