I store a 2001 Ram Air TA with the battery unhooked and on a float charger. I took it down off the jacks, hooked up the battery fired it up no problems.

Failed emissions test with a bone stock LS1 with under 16K miles.

I drove it 30miles and it still failed. Several items are "not ready" to test.

Why does power off the computer for an extended period of time (months) cause an OBDII to fail emissions test?

 

Don't have emissions here, guess your state does more than just the sniffer test. 30 miles probably didn't complete all the required OBDII tests. Maybe try www.obdii.com/drivecycle.html

 

You failed because the not ready signals. This is caused from a computer that is reset like yours. Your car probably will pass a sniffer but a lot of shops just read data off the PCM to see if any(at most 2-3) emission DTCs are active indicating a problem and youll fail the test. You just have to drive it around for so many miles/hours to get rid of the not ready signals.

 

Yes you may have to go through 2 tanks of gas to get enough monitors reading ready.
Mine's a 97 so I'm allowed 2 not readies vs your 1.(for 2000 and newer cars)
The EGR and O2 and O2 heater should reset within 100-150 miles, AIR and Catalyst will take a little longer.
My car doesn't have an EVAP monitor so don't know about that one.

 

Thanks for the link up there....that is what I needed. It sux when I'm preserving an F-Body with "minimum" mileage on it. I have had it over 3 years and put less than 1000 miles on it....now I gotta go drive it.....I'll just keep the battery hooked up and put the float charger on so that the computer does not lose it's memory.

 

As well as a certain number of miles or hours of ignition "on" time, the PCM might also need to see a minimum number of "cold" starts, with a minimum ignition on time for each, to count as a cycle. You're just going to have to drive it normally for a while. I know, it's not a daily driver, but you'll have to drive it like one...

 

I'll second that. I had the same proble with my Silverado. I ended up having to drive the truck to work a couple of days (I have a company truck). However you do have to do a couple of steps to get the readiness test complete. You have to start out with the engine cold and drive at 55 for about 10~15 minutes, let the vehicle cool completely, the do this step again at 65. If you do a search on my posts you'll see the complete procedure. However those two steps and drive it on a couple of 30~40 mile freeway trips will complete all the readiness tests.

 

I completed 2 GM drive cycles, about 40miles total and that was enough. Since I am a datamaster and LT1 Edit user for my 95, I went ahead and sprung for AutoTap, and it showed EVAP and Catalyst systems "incomplete" at first, but switched to complete and it passed.

 

Cool. Did you have to follow the drive cycles exactly like in the link - or just close?

 

I did not follow it exactly because where are you able to coast from 55mph down to 20mph without getting your gluteus maximus run over by probably someone else on this board......screaming....."if you don't know how to drive, you shouldn't be in an LS1 !!!!" with a few explicatives (colorful metaphors) thown in....

Just kidding....


I just coasted as much as I could.

This is a 16K mile 2001 LS1, so I bet an older car with more mileage would take more driving I would think....