2004 Honda Civic Si with code P0420
#1
2004 Honda Civic Si with code P0420
Hello forum members
I have 145,000 miles and have the CEL light on. Periodically, the light goes off..then comes back on. Had the codes read at Autozone and came up with the P0420 code:
Definition: Catalyst system efficiency below threshold bank 1
Probable Cause:
- A/F ratio concern
- Air Leak near H02S (Heated oxygen sensor) bank 1
- Ignition system concern
- Faulty catalytic converter
The car is running great; no change in performance or MPG.
Thanks in advance for any input/advice!
I have 145,000 miles and have the CEL light on. Periodically, the light goes off..then comes back on. Had the codes read at Autozone and came up with the P0420 code:
Definition: Catalyst system efficiency below threshold bank 1
Probable Cause:
- A/F ratio concern
- Air Leak near H02S (Heated oxygen sensor) bank 1
- Ignition system concern
- Faulty catalytic converter
The car is running great; no change in performance or MPG.
Thanks in advance for any input/advice!
#4
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Re: 2004 Honda Civic Si with code P0420
Sorry to bring this back, but I have the same issue. Are the sensors the same, but with a longer set of wires? Seems the only upstream sensors I find are stupidly $$..
#6
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Re: 2004 Honda Civic Si with code P0420
A p0420 means more then likely the car needs a cat. If the car had a faulty a/f or 02 sensor then it would have a defferent DTC then the p0420. The car trips that DTC when the computer doesn't see a big enough change between the primary and secondary 02 sensor readings. Now if the car had a p0420 and another code for the 02 system then I would start with the sensor. the faulty sensor may trick the PCM into seeing a faulty cat. But since there is only that single code it is safe to say your cat is bad.
#7
Re: 2004 Honda Civic Si with code P0420
Hi guys, long time Honda enthusiast, first time poster..
My FRS got totaled by a dumb kid a few weeks ago and I've been craving another naturally aspirated high revver... so... Honda.
I just drove a 2005 civic si and was taken back by how slow it was. After watching acceleration vids on youtube, I think this car was much slower than it should be. The CEL was on and the two codes that came up were both catalyst related, one of them being P0420, I forget the other one.
Question is: Would a bad cat really be hurting the acceleration that much?
There wasn't a drop of oil anywhere on the lower engine or trans, car was right around 100k, seems pretty well taken care of, maybe needs new cat AND tune up? I could feel vtec hit somewhere around 5 or 6 grand, but just not very strong.
My FRS got totaled by a dumb kid a few weeks ago and I've been craving another naturally aspirated high revver... so... Honda.
I just drove a 2005 civic si and was taken back by how slow it was. After watching acceleration vids on youtube, I think this car was much slower than it should be. The CEL was on and the two codes that came up were both catalyst related, one of them being P0420, I forget the other one.
Question is: Would a bad cat really be hurting the acceleration that much?
There wasn't a drop of oil anywhere on the lower engine or trans, car was right around 100k, seems pretty well taken care of, maybe needs new cat AND tune up? I could feel vtec hit somewhere around 5 or 6 grand, but just not very strong.
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