Code P0420

[abc_kid]

Hi guys,

Long time member, my car now has 210k miles. Only mods I've done are the EDM HID conversion and a Mugen Suspension setup. Recently, in the past six months, I've had a bunch of stuff go bad related to the engine:

Replaced Vtec Solenoid
Replaced Knock Sensor
Replaced O2 Sensor
Replaced secondary O2 sensor

My cat was actually replaced awhile ago and the mechanic said it looks relatively new. Unfortunately, recently I've had another code p0240 show up. Last time (like last month) we replaced the secondary O2 sensor which seemed to do the trick for only about 500 miles and it popped back on again.

I took it back today and my mechanic rechecked the sensor (it's working properly). He says my car is doing something weird, where the voltage to the secondary 02 sensor is pulsating, giving readings at 2,4,6, and then zeroing out, where the readings should usually be around 4 (sorry I forget what unit if it's ohms or what not).

Anyways, any advice? New cat? (although I think it was replaced at around 75k by my stealership.) My mechanic said it may be an ECU issue because he checked all the wiring and he said that looked good. Code was cleared again, but I'm sure it will pop up again. Thanks for any help.

[saidguler]

so last replacement of the cat was at 75k?

I assume you put 135k miles on it. I believe you need a new cat,

[L0ki]

Hi guys,

Long time member, my car now has 210k miles. Only mods I've done are the EDM HID conversion and a Mugen Suspension setup. Recently, in the past six months, I've had a bunch of stuff go bad related to the engine:

Replaced Vtec Solenoid
Replaced Knock Sensor
Replaced O2 Sensor
Replaced secondary O2 sensor

My cat was actually replaced awhile ago and the mechanic said it looks relatively new. Unfortunately, recently I've had another code p0240 show up. Last time (like last month) we replaced the secondary O2 sensor which seemed to do the trick for only about 500 miles and it popped back on again.

I took it back today and my mechanic rechecked the sensor (it's working properly). He says my car is doing something weird, where the voltage to the secondary 02 sensor is pulsating, giving readings at 2,4,6, and then zeroing out, where the readings should usually be around 4 (sorry I forget what unit if it's ohms or what not).

Anyways, any advice? New cat? (although I think it was replaced at around 75k by my stealership.) My mechanic said it may be an ECU issue because he checked all the wiring and he said that looked good. Code was cleared again, but I'm sure it will pop up again. Thanks for any help.

i'm actually having the same code, it's been pending during the time i got a smog check last december (luckily i passed, though i have a evap code as well i think). i've been reading around and it seems like that cat has to be replaced..but i've also read that it can be the secondary sensor. if you find a solution please do post it ! i'll be checking what i can do about it as well during spring break.

[turkish]

I got code p0420 (cat system efficiency below threshold bank 1) after i let my car warm up when it was covered in snow also snow was blocking exhaust. I redlined 4th gear on the highway and the code cleared. This was 6weeks ago. I read a post about this error and explains that bank 2 sensor needs to be cooler then bank 1 and I think the snow covered exhaust help produce this error code which is fine now, for me.

[klik]

I hated that code on my old ep3. I bought a kpro and new cat and thats how i pass smog even with the crazy california emmission shit.

[abc_kid]

Klik, did you have any issues with that Catco cat? Wondering if it will last. Yeah, my mechanic felt it might be an ECU issue because of the pulsating reading he was getting on the diagnostic tool

[Flip05]

any word on the catco cat? im also having the same prob p0420