Rep Power: 217

Just my luck. When it rains it pours I guess. Although I'm not too shocked. My car is approaching 140k soon. My car threw a p0420 code. Something about being below the catalyst threshold or something. Guy at Advance said he couldn't get more specific, but that's where I need to start. What am I looking at, guys? CatCon? O2 sensors? Leaky exhaust? NY requires my emissions be up to snuff, so I gotta get it cleared for good. It only seems to come on once I've been driving for a little while. If the result is a new CAT, I'm guessing OEM is the way to go? Guess it wouldn't hurt to get a new cover as well? I plan on driving this car until it no longer starts. I'm probably just gonna bring it by the guys who did my exhaust and have them double check everything before I start tossing money everywhere like I'm in a strip club or something.

 
Rep Power: 388

Usually its just the secondary O2 sensor that needs to be replaced. If that doesnt work, return the sensor and replace the cat with OEM.

There are also lots of other threads on this, just search "p0420"

 
Rep Power: 217

Thanks, Triz. Yeah. I thought there was. My phone doesn't seem to work very well with forum searching and I've been away from my pc the past few days. I'm assuming the secondary o2 sensor is the one behind the cat?

 
Rep Power: 235

Replace the sensor. If that doesn't work, replace the cat. The sensors should be replaced anytime you replace the cat.

 
Rep Power: 388

Yes, secondary is the second, or last sensor in your exhaust system, after the cat.

 
Rep Power: 200

i got obx header and full cat back, i only replace the front sensor.
car is at 137k miles and yes i do have emmission every year n
im on the same boat as u when it comes to inspections.
i thought i was going crazy with that code
it said bank1
its urs first sensor. i replace it at 100k other wise i fail emission.
another thing is that if u change ur air filter or go with intake u have more air going in
so it trips the cel light
i done this plenty of times on my si. the engine is sensitive to air diffrence.
i take some pics of my o2 reading both front and back

 
Rep Power: 217

It hasn't thrown a code since I made the thread yesterday. Put techron in the tank, though I doubt its going to do anything. Guess we'll wait and see! As for the intake, its had one in for as long as I can remember. It had one when I got the car. But, like I said, I'll have to wait and see what happens. I'll replace the o2 sensors though, because I know they do go bad. At least they didn't fall off like on my old Corolla. Lol. Long story.

 
Rep Power: 200

so i went to take some reading from my car
and here how it went
i got the obd2 scanner for 20 bucks off ebay
it was the best money spent cuz it hook up to ur laptop
then i got the laptop charger for 20 bucks so i can take readings while driving
and a laptop for 300 with 3 years warranty so still best money spent ha



on and another thing what i have notice is that everytime when the air in the atmosphere changes i have that code that was mention on this post and most of the time i just reset ecu
so from cold to hot like summer i would get the code but most of the time i just reset it without any problem
this is probly becuz i have a intake and aftermarket headers

so heres the program




so heres my o2 sensor reading both said bank 1 but it also say sensor 1 and sensor 2


here it is at 2k rpm as u can see sensor 2 has higher reading than sensor 1


engine seem to be running fine


so with this you able to source out the problem
and you can also reset the ecu with this software and get ur readings
if 1 one of the o2 sensor fail you will see very low voltage going to ur ecu
and it throws off a code

 
Rep Power: 217

Ha. That's actually pretty sweet. I did some searching on fleaBay and found one similar to that. I think I may just get it to have around just in case. I'm gonna pass some rep around since you guys have come through once again .

 
Rep Power: 200

i paid 20 bucks for the program
cuz the one came with the unit is just a demo
but if u get the same one i can hook u up with the program
same one that i have and also dyno tuned program so u can tuned it on the street

 
Rep Power: 388

Nice OBD2 tool, what seller did you get it from... link??

 
Rep Power: 200

http://cgi.ebay.com/ebaymotors/SCANN...motiveQ5fTools
this was the tool that i got

 
Rep Power: 200

yess it came from china but it work great
i also plug into any ob2 cars and get readings
its better than any portable ones cuz it gives you more details

 
Rep Power: 200

what i learn from this is the
Multi-Protocol Support:

SAE J1850 PWM (41.6 kbaud)

SAE J1850 VPW (10.4 kbaud)

ISO 9141-2 (5 baud init, 10.4 kbaud)

ISO 14230-4 KWP (5 baud init, 10.4 kbaud)

ISO 14230-4 KWP (fast init, 10.4 kbaud)

ISO 15765-4 CAN (11 bit ID, 500 kbaud)

ISO 15765-4 CAN (29 bit ID, 500 kbaud)

ISO 15765-4 CAN (11 bit ID, 250 kbaud)

ISO 15765-4 CAN (29 bit ID, 250 kbaud)

so if u buy any ob2 programs these is wat u look for ^^ so you know its compatible with your tool that if you want to go advanced

 
Rep Power: 0

Just had the same code thrown last night, Is there certaing symptoms that can help rule out other possibilities for the code poping up? At idle the engine sounds kind of rough as if it is starviing for air, the rpm drops and it makes a rumbling sound. Also some times when I fire up the engine it tries to stall for the first 2 seconds. I have that same obdII hardware, how can I see if the o2 sensors or working properly? At idle, from the live data they seem to be ok.