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Honda Ridgeline 2008 P0420 Code after extremely cold weather


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I have a 2008 Honda Ridgeline, well maintained by a trusted dealership.  I've had the truck since 2010 and it now has 260K KM (162K Miles).   Last week we had several days of extremely cold weather -24C (-11F).  (Western Canada)  While driving the check engine light came on.  I checked the ODB system and found that the P0420 code was the only error being reported.   This stayed on for several days with no additional codes.  

I tried to reset the error the first day but the check engine light stayed on.  On the weekend the check engine light has gone out but when I read the ODB system the P0420 code is still showing as present.   

Last year I had an O2 sensor error on Bank 1 and replaced the sensor. 

I've been researching this emission problem but don't know if this is a sensor problem caused by the sudden cold weather or if there is a problem with the catalytic converter system.   The truck drives fine.  Accelerates normal with no perceived loss of power.

Any advice on how to test the sensors to determine if they are a problem? Is this something that is known to happen with sudden extreme cold?  

If I need to replace the catalytic converters, are aftermarket reliable?  There are 3 on this truck. The OEM are almost 3 times the price of the aftermarket here in Canada. I typically have used OEM for maintaining this truck. Reliability has been great with minimum costs beyond the scheduled maintenance.  I just had the timing belt and water pump replaced as part of scheduled preventative maintenance. I still love this truck...


PS Though many people here scoff that its not a real truck. Its great in the snow and I can do most of my urban truck duties like pickup lumber and dirt (on the few times a year its needed), it can tow my family camping trailer, it is a pleasure to drive on the highways and it fits in my garage.


Thanks for your advice,



1 Answer

What, exactly, is a "trusted dealership?"  I have never seen one.  The pre-heater coil in one of the 02 sensors may have burned out.  Check them.

I met a customer that was getting his Toyota truck fixed at this Honda dealership because he had better experience with their mechanics than where he bought his truck from. They operate their service like an independent shop. I've gone to other dealerships in town but these guys atleast know their engines and have seen them rebuilding older civics and CRV's.

Anyhow, still having a strange issue with the P0420 code. I've tested and got voltages off Bank 1 Upstream and Down Stream Sensors and got graphs to compare to Bank 2. The voltages all seem to be in range. I've ordered new Air Fuel and O2 Sensors for both Bank 1 and Bank 2. But I had a shop recheck the computer and they were getting the P0420 but didn't see anything wrong either. They reset the computer and the code came back the same day. Someone told me to try use a higher grade of fuel for a few days and see if anything changes. I drove the truck for a few days on the highway and reset the error codes expecting the code to come back again. But now its been 3 days and the computer isn't reporting any error codes.

I'm not understanding why using premium fuel would have made any difference. I'm still expecting the error to come back. But would this give more credit to replacing the sensors?

I've got renewed vigor to fix my aging truck after going shopping for a new one and basically seeing what I get for $40K more than my old truck isn't really that much different. Just 13 years newer and probably even harder to repair.