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Truck Cant Get Through Emissions


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Alright my truck has failed emissions not once but twice. For some reason everytime they plug it up it doesnt read the computer and it fails. the evaporative system, heated oxygen sensor, oxygen sensor. I called Chevy and the told me if me since I unhooked my battery to install some new lights thats why it was failing but that was last sunday, then they said that it can take a day for it to reset to 10 days. Then they told me that the computer resets itself just by driving around and I asked them how will it pass since it does that and they couldnt answer my question but they get calls all the time about new gm trucks not passing all day long. my step dads 08 sierra was having the same problem. anyone got any ideas on anything?? :thumbs:

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Ive always heard that once you unplug the battery for so long and the computer resets then for the inspection to pass, you have to drive X amt of thruway miles , (not stop and go) so the sensors can relearn ... otherwise if it were that easy to unplug the computer and reset to fool the inspections, everyone would... :thumbs:

 

So to cure this, go take a small road trip, getting your truck up to operating temp, and cruise at highway speeds...

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The way I take his post is they are not making a connection to the computer. That would be a dead port. It shouldn't matter that he disconnected the battery. They should still be able to connect to the computer.

 

When you get it checked they look for trouble codes stored in the computer. I have took a scanner and cleared the computer just before I went to the inspection station and never had a problem.

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my truck has never had a dtc but i cleared them about a week before i had it tested. there is no reason why its failing nothing is done to it just a airaid intake tube and exhaust. My sheet from emissions says

OBD INSPECTION:

MONITORS NOT READY:

EVAPORATIVE SYSTEM

OXYGEN SENSOR

HEATED OXYGEN SENSOR

 

When it fails they give me this yellow paper that says that the computer has been reset and can take 2 or 3 days of normal driving to reset, and they also ask if i had any work done to it, battery died or changed the battery

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Maybe I'm missing the point, but if a 2008 wouldn't get through an emissions test I believe I'd be handing the keys to the service writer at the dealership and saying "Make it work." It's under warranty.

 

Exactly!! That is what federal Emissions warranty is for. So long as it has not been modded, let them fix it.

 

Keep us posted.

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Maybe I'm missing the point, but if a 2008 wouldn't get through an emissions test I believe I'd be handing the keys to the service writer at the dealership and saying "Make it work." It's under warranty.

 

A big +1

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First, they said to drive it for at least 10 days and try again and if it fails to bring it in and let them work on it

when you disconnect the battery, the ecm resets it self. what you have to do is go Thur what is called a drive cycle. so many starts and runs, allowed the ecm to recalibrate the emissions. after that it will pass.

i replaced my battery about 2 weeks before my smog test, and about 100 mi of driving all was good..

hope this helps

 

good luck

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HEY MODS :D

 

Is there a battery replacement sticky on here?? May be a good idea. Tell what has to be done, from having all accessories turned off,what to do after install, to how long you have to drive after wards for all to be reset.

 

What do you think??

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First, they said to drive it for at least 10 days and try again and if it fails to bring it in and let them work on it

when you disconnect the battery, the ecm resets it self. what you have to do is go Thur what is called a drive cycle. so many starts and runs, allowed the ecm to recalibrate the emissions. after that it will pass.

i replaced my battery about 2 weeks before my smog test, and about 100 mi of driving all was good..

hope this helps

 

good luck

 

 

This is correct, if you reset DTCs or anything soon before the test they won't pass you because you could be trying to get it passed with a DTC that's just delayed or something. Plus the computer needs to adjust the parameters properly. There's a company out there that sells a little device that plugs into the ODBII port and has a red and green light, all it does is let you know if it's been driven long enough since a reset to go in for a smog test.

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  • 4 months later...

I have a 04 GMC Sierra with the same problem. They can scan for MIL and DTC, but the Catalyst Efficiency, O2 Sensor, and Heated O sensor come back Not Ready. The "Air Team" gave me the same song and dance about driving cycles. I have put 8,000 miles on since changing the battery and the test results came back the same Not Ready.

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  • 5 years later...

The way I take his post is they are not making a connection to the computer. That would be a dead port. It shouldn't matter that he disconnected the battery. They should still be able to connect to the computer.

 

When you get it checked they look for trouble codes stored in the computer. I have took a scanner and cleared the computer just before I went to the inspection station and never had a problem.

 

 

I know this is now 6 years later, but I worked for nj state inspection and people would clear their codes all the time trying to "trick" the computer into thinking there were no codes present, however, the software we used, would fail you because it would show up as those sensors not being ready.. So it may depend on where you live.. But states with strict emissions laws will likely have similar emissions testing to nj..

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