P0420 Trouble Code
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P0420 Trouble Code
My check engine light just came on. Read it and came back P0420, Upstream catalytic converter (left clinder bank) efficiency. Anyone have any idea where to start on trying to fix that?
I was gonna start with plugs, wires, simple stuff.
Thanks, Jake
I was gonna start with plugs, wires, simple stuff.
Thanks, Jake
Record Breaker
Joined: May 2009
Posts: 1,130
Likes: 1
From: Eastern, NC
Well, could have started with a search for p0420 and should have gotten you plenty of info. But, since you didnt do that, that code comes from the downstream o2 sensor and indicates a catalytic deficiency. In a perfect world, it means your CAT is not working properly. When accompanied by a sudden, noticeable drop in mpg, it is a pretty sure bet the CAT is failing. However, it is not a perfect world and an upstream exhaust leak or simply a faulty sensor can also cause that code.
So, first check for exhaust leaks upstream of the sensor. Next step would be ro replace the sensor itself with a quality one (by quality i mean one that doesnt come from Bosch). If those steps fail, then you probably need a new CAT. I had this code on one of my other vehicles and it just needed a new sensor.
So, first check for exhaust leaks upstream of the sensor. Next step would be ro replace the sensor itself with a quality one (by quality i mean one that doesnt come from Bosch). If those steps fail, then you probably need a new CAT. I had this code on one of my other vehicles and it just needed a new sensor.
Last edited by 04HemiGreg; Aug 30, 2012 at 10:23 AM.
Professional
Joined: May 2009
Posts: 123
Likes: 0
From: West Point, Kentucky
Well, could have atarted with a search for p0420 and should have gotten you plenty of info. But, since you didnt do that, that code comes from the downstream o2 sensor and indicates a catalytic deficiency. In a perfect world, it means your CAT is not working properly. When accompanied by a sudden, noticeable drop in mpg, it is a pretty sure bet the CAT is failing. However, it is not a perfect world and an upstream exhaust leak or simply a faulty sensor can also cause that code.
So, first check for exhaust leaks upstream of the sensor. Next step would be ro replace the sensor itself with a quality one (by quality i mean one that doesnt come from Bosch). If those steps fail, then you probably need a new CAT. I had this code on one of my other vehicles and it just needed a new sensor.
So, first check for exhaust leaks upstream of the sensor. Next step would be ro replace the sensor itself with a quality one (by quality i mean one that doesnt come from Bosch). If those steps fail, then you probably need a new CAT. I had this code on one of my other vehicles and it just needed a new sensor.
He basically hit the nail on the head there. In my experience mine has always been the damn "CAT", never the O2 sensor which would have been nice. But my last vehicle got lucky and was still in the 8 year, 80,000 mile epa warrenty and was replaced for free; thankfully.
But just start diagnosing things or if you got a buddy at a dealer have them test it. It might even be worth it just to pay the 80-90 bucks for the diagnostic fee to know exactly whats wrong if you can't seem to solve the issue. Nothing worse than throwing money at the truck over and over trying to fix it on a prayer and it not fix the issue.
