So Ive failed emissions twice now.

[OffshoreDrilling]

I took my car for emissions last weekend and ended up failing. The front O2 sensor wasnt ready. They told me that there is nothing wrong with the car, and I just need to drive it more. Well, 400 miles and a week later I went back and the same shit again. Ive got one more chance to take emissions, and its due by June.

I was doing some scans yesterday and noticed my O2 voltages are really erratic. At WOT they usually sit around 890mV give or take about ten. My scans had them at around 890mV then they would drop to 20 or 30mV randomly.

The car isnt throwing any codes, but to me its looking like the O2 sensor is acting up. I dont want to go out spending money and throwing parts at something not broken. Im just looking for some opinions besides my own. A few of you guys work at dealers, so I though you might be able to throw some advice my way.

Click to read more...

 

[Turbocharged400sbc]

backprobe the signal wire on the sensor connector (at the O2 connector, also as a control you can do this at the PCM if your carefull with a thin T pin) and hook up a dvom and go for a drive compare your readings.

by now all of your drive cycle test should have run, have you had alot of that driving as steady 45mph+ cruise/light accel/decel? this is where most diag monitors are run on the evap/sensor response etc

i've had bad o2's more than a few times that didnt trigger a ses light so yes it can be bad

 

[OffshoreDrilling]

backprobe the signal wire on the sensor connector (at the O2 connector, also as a control you can do this at the PCM if your carefull with a thin T pin) and hook up a dvom and go for a drive compare your readings.

by now all of your drive cycle test should have run, have you had alot of that driving as steady 45mph+ cruise/light accel/decel? this is where most diag monitors are run on the evap/sensor response etc

i've had bad o2's more than a few times that didnt trigger a ses light so yes it can be bad

I'll pull out my meter and try that out. About 200 of those 400 miles were highway, between 60 and 90mph for about an hour at a time

 

[EmersonHart13]

G2P (Guaranteed to Pass) AND a full take of Mobil 93... Run it all the way out, then throw in a few gallons of 93 from Amoco/BP... Drive around with the AC blasting, get the car good and hot...

Then test, works "every time."

 

[Bob Kazamakis]

i'm confused. they plugged it in and it said the 02 wasnt ready? i had thought they only checked for dtc's or pending codes.

 

[Nasty93]

your saying the front 02 goes from 900 ish to 50 ish?
thats because it supposed to, its called Min/Maxing. The engine monitoring O2 is supposed to jump, The catalyst monitoring one is supposed to stay at about 450mv (stoich)

 

[Nasty93]

oh yeah, if it says its not ready, sounds like a heater issue

 

[OffshoreDrilling]

your saying the front 02 goes from 900 ish to 50 ish?
thats because it supposed to, its called Min/Maxing. The engine monitoring O2 is supposed to jump, The catalyst monitoring one is supposed to stay at about 450mv (stoich)

Ahh, okay. Ive never knew that. I just know what voltage I want it to be at for tuning purposes. Im going to ohm out the heater circuit, since you said that may have taken a shit.

I'll get back to you guys with what I find.

 

[DanJ]

I'm not sure that the state of illinois checks the heater function. I tested a couple weeks back and under O2 Heater it said "Not Supported".

 

[02BlueGT]

i'm confused. they plugged it in and it said the 02 wasnt ready? i had thought they only checked for dtc's or pending codes.

Emissions tests are often misunderstood, all OBD2 cars have what are called readiness monitors, While most of your emissions equipment is running continually, it only gets tested during very specific conditions of load, temp and many other variables. The readiness monitors can be in 3 positions, not run, run/pass, and run/fail. If they say it is not ready than the monitor hasn't run yet. When you delete codes it resets all monitors to not run, so that is why you cant clear a code than just go pass emissions....

now to the issue at hand, Do you have a stock temp thermostat, or a lower one, cause the 02 readiness monitor probably requires operating temp of 180*(just a guess)..... A full mod list may help us diagnose :smile:

 

[OffshoreDrilling]

didnt know about the deleting codes thing. I think that my have been my problem. This past time Im positive that I deleted some codes right before I went to have it tested. Last weekend, I may have also, but cant remember for sure

 

[02BlueGT]

Deleting codes will cause a no-pass....Drive at least 200mi in varying conditions after code deletion to make sure monitors have run, some scan tools can tell you if the monitors have ran

 

[Lord Tin Foilhat]

Emissions tests are often misunderstood, all OBD2 cars have what are called readiness monitors, While most of your emissions equipment is running continually, it only gets tested during very specific conditions of load, temp and many other variables. The readiness monitors can be in 3 positions, not run, run/pass, and run/fail. If they say it is not ready than the monitor hasn't run yet. When you delete codes it resets all monitors to not run, so that is why you cant clear a code than just go pass emissions....

now to the issue at hand, Do you have a stock temp thermostat, or a lower one, cause the 02 readiness monitor probably requires operating temp of 180*(just a guess)..... A full mod list may help us diagnose :smile:

correct

 

[DanJ]

if you deleted codes then that's it. I did the same thing. You need to get the codes taken care of.

 

[02BlueGT]

correct

What do I win :smile:

 

[Lord Tin Foilhat]

5$ for the casino

 

[OffshoreDrilling]

if you deleted codes then that's it. I did the same thing. You need to get the codes taken care of.

There are no codes.... anymore. My TPS was acting up so I unplugged it and plugged it back in. When I started the car it threw a code, so I removed all the DTCs with my powertuner. Then the next day, I cleared them again to make sure nothing was on there before I tested. I guess I fucked myself then.

Hopefully thats all it is now, because this is my last try at it.

 

[Bob Kazamakis]

is your tps still good? that could cause a whole host of issues if its still acting up.

 

[OffshoreDrilling]

Its working fine right now, and no problems in the past. I started my car and it was idling at 1800 rpms. My IAC count was good so i messed with the TPS. Its been working fine now.

 

[DanJ]

if you're "rejected" again you can go to the DMV and get a 7 day registration pass for 10 days while you get your issues worked out.

 

[Chrisco]

Also to ensure all ready checks have been made, be sure to drive the car ALOT directly before you go to the DMV. Don't just do the highway cruise it might take you to get there. Put 10-15 miles on it in town too and make sure it's at full operating temperature. This was more of an issue with OBD1 cars, but again it may help to ensure all ready checks have been completed.

 

[OffshoreDrilling]

Thanks for the advice guys, I plan on re-testing this saturday. Hopefully the problem is just my dumb ass clearing the codes both times.

 

[OffshoreDrilling]

Just got back from emissions, and I passed. It was because of deleting fucking codes. Damnit.