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Discussion Starter · #1 ·
I have a RR HSE 2008 with 101k miles on it. During a long drive (at the 9 hr mark of a drive with maybe 2 stops of 15 min each) the check engine came on. The code is p0420catalytic converter insufficiency bank 1. This is the 3rd time it has come on, all after several hours of driving. I erase the code and then it doesn't come back until another long trip. It also does not come on with all long trips.
Any suggestion on what this is? what should i do?
thank you again to everybody for you valuable assistance in the past
 

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P0420/430 faults can only be caused by catalyst efficiency being low. That said, there are many things that can cause low cat efficiency other then the cats themselves.

Anything from incomplete combustion to burning oil to a failing thermostat. Step one with this is to have a full tune up, spark plugs, capacitor, PCV valve, and an induction service if there is any carbon fouling/oil in the intake. This will correct most of the outside sources that can cause cat efficiency to lower. Clear the faults, reset the adaptions(hard reset on the battery will reset engine adaptions) and see what happens. These cats are pretty good, but I have seen several fail, but most of the time I see these faults, they are caused by outside sources, and not the cats themselves.
 

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Discussion Starter · #3 ·
Dave
thank you for the feedback. Over the last 6 months this code has come up about once every 4-6 weeks. I erase the code and keep driving. I haven't done a hard reset. How do you do this? also, my mechanic said that it can be oxygen sensors, catalytic converter or even the gas that i use. the last time this code came up was 3 hrs into a driv, about 20 minutes after filling up the gas tank... any thoughts? suggestions? rover runs great and i love this truck.. hoping to get many more miles out of it.. i hav 115 k miles now.
 

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I had the same P420 error code. It came on and stayed on constantly. I had the dealer do the induction service, changed the gas, PCV valve, etc.. etc.. Nothing helped. I eventually had to get a new cat and the problem went away.

I also live in California, so I was raped on the new cat since California has draconian emission rules and I couldn't buy an aftermarket cat.

What I also learned from the dealer is that on these rigs, the P420 code is very specific to the cat and doesn't generally mean the sensors are bad unless the error is intermittent OR it is coupled with other error codes.
 

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Discussion Starter · #5 ·
so when i erase the code and then the code doesn't come back for several weeks or even months, what does that mean. i drove for 8 hrs o ver an 10 hr period yesterday (hghay miles) and no issues. does this mean anything?
 

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so when i erase the code and then the code doesn't come back for several weeks or even months, what does that mean. i drove for 8 hrs o ver an 10 hr period yesterday (hghay miles) and no issues. does this mean anything?
Not sure. Mine would trigger a "pending fault" within a day, and then it would "hard fault" (with check engine light) within 48 hours.
 

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Discussion Starter · #7 ·
since this code seems to come on some of my long highway driving trips, does this help in making a diagnosis?
Thank you to everyone for all your help. Without this forum Id be in big trouble.... and poorer
 

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Discussion Starter · #8 ·
p0420 code came up last at 120k miles. i now have 149000 miles on my 2008 range rover hse.... not sure what caused this, but i have used bg44k a few times over the last 50 k miles....... can that have helped? or was it more due to gas. i stopped using a particular BP gas station several years ago as well, so not sure if that caused this.
figured id update the group
 
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