joeli27

Hi guys, here are my problems. I just had a b16a2 swap into a 96 civic cx about a month ago. After the swap was done my cel came on and i pulled the code. It was the primary o2 sensor. I replaced with a ntk o2 sensor and i also cleaned the TB and IACV. The code for the primary sensor was gone but there's another code. The new code was for the iacv. I replaced it with my friend's b16a iacv and it works fine and the code was gone. Just the other day i was driving on the highway, the cel came on again (only comes on during highway speed). This time it was the Catalyst low efficiency P0420. What does that mean? Does it mean my cat converter is bad or the rear o2 sensor? It is a Magnaflow 2 inches universal cat converter. I brought it brand new. So i don't think is the cat converter. Would it be the rear o2 sensor that gone bad? I am sure someone had this problem before with P0420 catalyst low efficiency. How did you fix it? Any help and suggestion would be very helpful? Thanks

joeli27

will the blox cel eliminator work? cause i see some people use that for test pipe and high flow cat

SiR831

Cat is Bad....Catalyst isn't operating efficiently anymore...

phootbag

The monitor P0420 evaluates the secondary oxygen sensor feedback voltage pattern. If the voltage pattern nearly matches the primary oxygen sensor feedback voltage pattern the monitor fails and P0420 sets.

I have never seen a failure of a secondary oxygen sensor which caused a false P0420 to set. OEM catalytic converters are expensive but what's more expensive is buying countless aftermarket catalyitic converters that only last a short while. There is a reason factory cats cost more.

honda_luvr_2000

Aftermarket catalytic converters are much less efficient and much closer to the efficiency threshold limit than factory catalytic converters. Yes more than likely it is your aftermarket Magnaflow catalytic converter that is setting the code. P0420 will "never" set for a bad O2 sensor & I have yet to see it falsely set for a catalytic converter that is okay.