dustinthehawk

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!

nahonda04

o2 sensor needs replaced

SickSi99

^This. Bank 1 sensor is the front sensor off the manifold.

BigZ88

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 $$..

BONTY_EP3

your cat is done.

SlowIntegraLS

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.

HerrFunf

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.