TL;DR - I've started seeing P0420 and P0466 check engine lights (CELs) as often as once a day on trips.
Easy to clear but still annoying.
I've been getting a P0420 check engine light (CEL) every now and then for about the last three years. It's been infrequent enough that I've mostly just cleared it using my Kiwi 3 OBDII Bluetooth Adapter (here's a cheaper alternative) and kept on with my day.
However, in the last six months, it's started to become more frequent, and in the last three months I've also begun to get a P0466 - EVAP Purge Flow Sensor Circuit Range/Performance - every now and then, perhaps related to the strange clicking that I heard coming from the gas tank area, which I blamed on Fred the Marmot - when we were in the Canadian Koots.
Now that I'm getting these more regularly, I'm going to look into whether there are easy solutions. Cleaning the MAF, perhaps a new rear O2 sensor, maybe a EVAP purge valve if they aren't too pricey. I'm not planning to go as far as a new Catalytic converter - if it comes to that - though.
Easy to clear but still annoying.
In this Series
![I've Worn Out My TPS (Throttle Position Sensor) [P0120 Check Engine Light]](https://live.staticflickr.com/65535/54550578694_197ca25c09_c.jpg "I've Worn Out My TPS (Throttle Position Sensor) [P0120 Check Engine Light]")
![My Cats are Empty [P0420 Check Engine Light]](https://live.staticflickr.com/65535/54550567999_6bda364eed_c.jpg "My Cats are Empty [P0420 Check Engine Light]")
Ah the dreaded P0420 code. Eventually caused me to get rid of my late, not-very-lamented Subaru Outback. I'm with Todd on the magic elixir though eventually I was backed into the replace-the-cats corner. Hopefully you will fare better.
As for that UBJ cotter pin, eeeuuuwwww... that would never pass muster in the aviation world. Add a washer under the nut to space it down a bit. Inconvenient at this point but really, easy-peasy.
And thanks as always for the thoughtfully written how-to's. Always enjoy them.
Agree a washer sounds like a good idea. I have seen some thick Grade 8 washers at Ace that might be just the right fit.
Cat getting worn out for P0420 code maybe?
Possibly; details of what I think it could be in the story... going to try MAF And O2 first.
Could try cleaning MAF if you want as a dirty MAF can set a lean coded but that's usually a P0171 code. P0420 is a specific code for catalyst efficiency which can be a worn out convertor or possibly a post cat 02 sensor. I doubt the MAF is gonna fix anything. Obviously remote keyboard diagnostic but I am a retired 30yr ASE former tech and shop owner so have a little experience to help the keybord diagnosis a bit.
Yep, I always appreciate any insight. I've had the P0171 before and that turned out to be the MAF; hoping this one ends up being the rear O2, and I figured that cleaning the MAF at the same time would just be "good hygiene."
I will of course keep everyone posted as to the results! 👍
If you have access to a scan tool not just a code reader you can access the 02 sensor readings pre and post convertor. There should a drastic change in readings from pre to post cat sensors with a good convertor. The post cat 02 sensor reading should be much more sluggish and more of a flat line if the convertor is doing its job and the 02 sensor is good. Obviously if the post cat 02 sensor is bad then that throws things off as thats how OBD determines the efficiency of the convertor
Interesting. My OBDII dongle does do scans, so I'll pop into that mode and see what I see. It was super cool to watch the LTFT and STFT numbers as I was diagnosing the P0171 I got many years ago now.
Even if the rear O2 sensor is bad, it'll be cool to compare graphs for the bad sensor and good sensor and include those in the write-up of whatever the solution ends up being.
Thanks for the suggestion.