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My 09 2.5i Impreza with 75k miles is showing a P0420 code. Catalyst System Efficiency Below Threshold (Bank 1).
This showed up a day ago right after I refueled at a Sams club in NJ, not sure if this had anything to do with it. About 2 weeks ago I had the car at the dealer for a oil change and they reminded me that my inspection is due in 2 months, not sure if this has anything to do with it.
I cleared the code and during a round trip from PA to DC, the light came back on during the trip back to PA. I want to run this tank of gas out and refill at my normal local gas station in PA to see if that will help.
My question is what can I do to investigate this before spending money. I do have a infra-red thermometer and read that it can be used to help diagnoses, but nothing I found online gave a clean how to.
Any help would be awesome!
Thanks!
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Check if there is a leak in exhaust, that’s the biggest cause for that code to come on, resetting code without doing anything could cause it to come back on, if determine there is no leak than the cheapest way is to change all O2 sensor.
Thx, not sure how I missed that video. I wanted to hop under the car today, but its raining. For now I’ll just use my scan tool.
I check the reading with my cheap scanner. I can only read O2 sensor bank 1 sensor 2 (not why I cant read sensor 1), which I think is the one after the cat. It jumps around like the one in Eric’s video. I can’t do a temp check today, but its this looking like a bad cat?
Also, the sensor after the cat is the downstream correct?
Most of the time when I see that code, it’s a bad catalytic converter. Do the testing as shown in the video and that should tell you if that’s the case or not. One thing to note, not all cats are created equal. I’ve had issues with some aftermarket catalytic converters causing the same code to come back even after replacement. If you go aftermarket, look for a quality part to avoid this issue.
Good luck and keep us posted.
I’ll check the temp tomorrow once it has stopped raining. I’m really hoping to avoid buying a new catalytic converter.
Also, I been reading around some more and found that there is a EPA warranty for 8 years or 80,000 miles.
EPA.gov PDFI have to call my local office in my state (PA) to double check this, but I may be covered on this repair.
I’ll post back tomorrow.
I drove for about a hour and did the temp test. I got about 360F before the catalytic converter and 260F after. Based on the video, it should be a higher temp after.
I also spoke with someone from the EPA and IF it is a bad catalytic converter, its covered. Looks like I’m making a appointment to the dealer.
Yep, the cat should be cooking and the outlet temp should be MUCH hotter than the inlet temp.
You also need to worry about WHY the cat failed. They don’t just crump on their own, either it burnt up due to too rich a mixture or misfires, or got covered with some glop that was in your fuel, like leaded gas or a gas tank additive, maybe. So you should first ensure that the engine is running well and there is no glop in the gas before plunking in a new cat converter.
I never had any issue with the engine, never added any additives, and I owned the car for a year (2nd owner). This is my first CEL. I had a oil change about a month ago from the dealer and was told I need to replace my drive belt, but I don’t think that has anything to do with this. The only thing I can think that may cause this was fueling up at a Sams Club in NJ. The light came on within 10 miles after filling up. I normally use Shell, Sunoco, or the Sams Club in PA. Never has any issues with them.
*Update*
Drove the car last night and no CEL lights. I filled up at a Hess the day before. I still have appointment with the dealer. I plan on refilling at the Sams club tomorrow to see if it comes back on.Last update
Dealer fix the issue, bad cat. Everything was covered and I got to drive a 2013 Legacy for the day.
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