Check Engine Light Came On Again, Code P0420 Options

[LewFX]

I got a new code after i got the header on, P0420, catalyst effieciency below threshold...so either the O2 sensors are bad or not tight enough?

This post has been edited by LewFX: May 27, 2006 - 2:53 PM

[Batman722]

try reseting the ECU and seeing if it comes back again. Sometimes it will be nothing, sometimes it won't.

were you driving your car hard when it happen (high RPMs) ?

it happen to me once, I was behind a friend (about 60ish mph) and I dropped it in 3rd and pulled hard around him to be cool. My CEL came on and when I checked it it was my lower 02 sensor. The light went away a few minutes after the pull, I reset the ECU the next day and haven't gotten the code since.

[LewFX]

first i tried resetting the ecu and it came back and now i just erased the code and nothing yet.

This post has been edited by LewFX: May 28, 2006 - 12:14 AM

[presure2]

make sure the plug is securly connected

[toyotacrazy]

Do you have a catalytic convertor? If so its probably deteriorated.

[presure2]

Do you have a catalytic convertor? If so its probably deteriorated.

I got a new code after i got the header on

he dont have the primary cat anymore.
thats prolly part of the reason for the code.

[LewFX]

still no problems with it yet, as soon as the light comes back ill let yall know

[bindertch]

If it does come back on you should think about moving your sensor to after the second cat. I was fine for about a year without the rear sensor and then all of a sudden the CEL came on and even after clearing it it comes back so I am looking into the cure. It won't help you pass emissions but it will help cure the sensor issue.

[LewFX]

well today the CEL came on again, what to do now...car still runs fine to me.

This post has been edited by LewFX: Jun 1, 2006 - 8:11 PM

[Bitter]

some 3rd gen eclipse folk have had luck using a spark plug anti-fouler to space the sensor out a little so it gets a cleaner sample and doesnt trip the light. but im not sure if this would work for the toyota sensor, it needs to be the kind that screws into the pipe, not the flanged type.

[LewFX]

the guy who sells the header told me that it was suppose to come with a bolt end for the bottom hole...which piece is the actual o2 sensor? the top or bottom? should i cap the bottom and hot wire the bottom wires into the top wires?

[Bitter]

ok, does your car have a black plastic thing near the drivers side strut tower that says diagnostic and do you have a multimeter?

[LewFX]

diagnostic

[LewFX]

bump

[Bitter]

diagnostic

look in the cap of that port and you should see someting labeled OX1, OX2 and E1. hook the OX1 to the red meter lead and the E1 to the black lead and read the volt scale, then do the same with the red lead in OX2. make sure you use a computer and sensor safe meter.

OX1 should read an average of .5-.45 volts, it will fluctuate up and down from .8ish to .1ish which is normal.

OX2 should read fluctuations as well, but much smaller and be stable around .3 or .4 volts i beleive. im a bit fuzzy on what O2 sensors read post cat.

[LewFX]

possible probs are:
1) three-way catalytic coverter
2) open or short in oxygen sensor
3) oxygen sensor

[bindertch]

The problem is that the second O2 sensor is suposed to be reading after the first cat which with a header like mine you removed it. If you get it inserted in the pipe just after the second cat it should get a low enough reading that you won't get the CEL but it won't help your emissions. I hope you kept what you could off of your stock manifold so that you can put it back on when it comes time to pass smog.

This post has been edited by bindertch: Jun 5, 2006 - 6:41 PM

[LewFX]

ya i kept everything when i get it smogged. so theres no way at all that it will pass!?

[LewFX]

well bought a new O2 sensor and reset the ecu, hope this rids this problem

[toyotatech]

well bought a new O2 sensor and reset the ecu, hope this rids this problem

it won't, the second o2 sensor is just for monitoring the cat and if you removed it they are seeing a problem