Car failed the hi nox area of emissions. Ive replaced the cts and pcv since. Just wondering if I should pull codes even though i'm NOT getting any cel's. Car is driving fine otherwise and idling under 1k. Noob question but i'm a bit unfamiliar with toyota. I thought cels usually came on after something went bad.

 

When a vehicle fails for high NOxs its most likely the EGR, EGR modulator, or the VSV that controls the EGR modulator. The Catalytic converter also can contribute to NOX failures but should be the last option.

Do some tests on the EGR components to see if they test out fine.

 

Thanks. I'll have to do a more thorough check. I did check for codes and got nothing.

 

high nox means your running lean. Change your fuel filter and retest. That would be my first step if it hasnt been done.

 

I'll give that a try as well. I wish i didnt have to test everytime to figure out if everything i've changed actually worked.

 

You can also try a gallon or 2 of alcohol in the tank after you change the filter... high nox can ultimately mean bad cats, but i start with the easy fix first.

CO gives you one free retest for every paid test. Does GA do that?

 

Got my free retest today and failed Nox only lol. Which is rather annoying considering I have no codes.

 

Yeah its not always something that will cause a CEL. most cars arent that smart.

 

Well i guess my next question would be, how do you test for a bad cat

 

How many miles are on the car? What year and is it a 2JZ or 1UZ?

Hows the numbers look on the HC's and CO? If the HC's and CO are high, your CAT is shot.

But like mentioned before, this should be the last option cause CATs are so expensive to replace

 

these can cause high nox: bad o2 sensors, dirty maf, egr problems, bad/cheap gas.

 

post up the readings on all the gases.

 

Like I said its only the NOx area i'm having issues with. 92 Sc4 btw. Sorry fot the crap cel pic

 

I'll put money on it that its your EGR modulator or the EGR valve itself.

HC's and CO are really low so the CAT still good. I see this all the time when Toyota/Lexus FAIL NOXs.

 

EGR is a good bet since its a sc4. I would still change the fuel filter too, just to be sure.