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Old 12-15-2008, 08:28 PM   #1
Scooby Newbie
Member#: 196946
Join Date: Dec 2008
Chapter/Region: NWIC
Location: WA
2007 Wrx limited WRB
07 FXT WRB,'15 model S

Default CEL P0420 + shift RPM question (5th to 6th)

So I've only had my 04 STI for a bit over a week now so I'm still getting used to the beast In that week + a couple days I've thrown my CEL almost every day. I had the code pulled and it was P0420. Depending on responses a trip to the dealership is around the corner but posting this question here first.

What RPM/speed do you shift from 5th to 6th? My previous car was a BMW which had more torque so I just always shifted low and was in the highest gear possible. I've noticed when I throw the CEL I've ended up being in 6th gear at 60MPH or just below (maybe 55mph or so by mistake).

Am I just lugging down the motor thus causing the CEL because of my habbit to be in the top gear on the freeway or does this sound like a problem with my O2 sensor? The car only has 31K miles on it so I highly doubt its the CAT thats the problem which leaves me thinking its the O2 sensor.... Or maybe my driving thats at fault

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Last edited by Screwbal; 12-15-2008 at 08:40 PM. Reason: formatting
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Old 12-15-2008, 08:51 PM   #2
Scooby Guru
Member#: 21808
Join Date: Jul 2002
Chapter/Region: E. Canada
Location: National Capital Region
02 GroceryGettAr
Nonemore Black


it's just that the ECU performs the catalyst efficiency check at that particular cruising RPM

nothing to do with your shift habits

the most common cause of that code is running a catless aftermarket downpipe - if your car is stock then yes a failing cat is the 2nd most common
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