failed smog but not because of emmisions?

[mattss90]

Hey all,

i think this is my first post here, so sorry if this is in the wrong spot. but i recently obtained a 96 2 door Tahoe that runs like brand new. ONLY 78000 MILES! I went to have it smogged because it's due in February and it failed smog. Not because of bad emissions (passed like it was brand new) but because of it not being mechanically sound.

Has anyone ever heard of this or experienced this? did the tech doop me so I'd come back for a retest? He said it could be from the computer malfunctioning or from me disconnecting the battery. He said I need to drive it up and down the highway for 20 minutes so the computer can reset itself and then bring it in. I replaced the battery 2 weeks ago which since then I've been on a road trip which definitely was longer than 20 minutes.

Any help or experience with this issue would awesome. Thanks in advance!

 

[TxDrewski]

"Mechanically Sound" is a very broad subject. But, you cant fail a "smog" test for anything other than emissions...Somethin smells fishy...

 

[mattss90]

i just looked at the paper he gave me. it passed emmisions tests at 15mph and at 25mph. and failed the functional check. something to do with the air injection.i did install an aftermarker K&N performance system. but that still doesnt explain the whole battery and computer conversation i had with the guy.

 

[TxDrewski]

Id have me a 2nd opinion lol.

 

[SunlitComet]

It sounds sorta like the computer was not in a state ready for testing. Specifically the inspection readiness monitors. If you disconnect the battery for a given time these monitors resets and the vehicle needs to be driven for a while for the computers performs some internal testing of its own to know it is ready for emissions testing. Do your normal driving routine as return for the retest before the free retest time frame runs out.

 

[CaliBoi209]

I had that same issues on my little commuter car. The check engine light was on because of the cas cap not sealing correctly and I disconnected the battery and the light went off, but during the smog check it still registered and a fault in the cars computer being that it didn't clear on it's own.

 

[mattss90]

Thanks sunlit. That's the conclusion I was starting to come up with. I took it back in after driving it for 15 miles on the highway and it still wasn't able to register the monitors. The cat and the O2 sensor monitors aren't ready for testing so I'm gonna make a little road trip today and hope that helps to do fix it. I had read somewhere that using all your accessories like AC rear defrost etc. would help the computer kick in due to high use of the vehicles features. Idk if it's true but I'm gonna give it a shot

 

[SunlitComet]

Ideal method.

 

[mattss90]

Awesome. Where did you find that?

 

[SunlitComet]

In the service manual. But this and much other data has been published in the open.