O.k. now that I have your attention (I hope). I have a problem. I'll break it down below and maybe one of you LS1 truck geniuses can help me (I mean that in a non-sarcastic way, trust me).

Went to get my truck smogged today and it failed because I reprogrammed my truck back to stock. I have an aftermarket power programmer. I won't go into any details about the programmer because it's not important. Reason it failed was because my truck's computer was still in it's "learning stage" according to the smog guy. He said this happens when you reflash your computer or disconnect the battery.

Well, I'm trying to sell my truck ASAP so what does it take to get the computer to complete this learning process (or whatever it's called). One Chevy dealer told me it takes two days of driving and another told me to put about 100 miles on the truck for it to re-learn what it needs to learn. What do you guys think? Thanks!!!

 

I was told about 50-100 miles will re learn a pcm

 

A hundred miles should take care of It

 

That and it will have to go through a few drive cycles........not sure how many though.........

 

Ive heard the same as mention by everybody, about 100 miles

 

Do this and follow to the letter. It works, I've done it.

GM Driving Cycle

A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.


This is how to perform an OBD Type II Driving cycle:



1.) Cold Start. In order to be classified as a cold start the engine coolant temperature
must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature
at startup. Do not leave the key on prior to the cold start or the heated oxygen
sensor diagnostic may not run.



2.) Idle. The engine must be run for two and a half minutes with the air conditioner on and
rear defroster on. The more electrical load you can apply the better. This will test the
O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved,
Fuel Trim.



3.) Accelerate. Turn off the air conditioner and all the other loads and apply half throttle
until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge
Flow diagnostics will be performed.



4.) Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During
this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim
diagnostics will be performed.



5.) Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.



6.) Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will
perform the same diagnostics as in step 3.



7.) Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes.
During this time, in addition to the diagnostics performed in step 4, the catalyst
monitor diagnostics will be performed. If the catalyst is marginal or the battery has
been disconnected, it may take 5 complete driving cycles to determine the state of
the catalyst.



8.) Decelerate. This will perform the same diagnostics as in step 5. Again, don't press
the clutch or brakes or shift gears.

 

Wow, thanks for the info. GREGGO. I just got back from a trip to a friends place. Just so happens it was just over 100 miles (round trip). But, it was all pretty much varying freeway speed (65-80 mph). I did notice that my speedo needle was kinda sticking when I got home (after the trip) when I was on the streets around my house. The sticking I'm talking about was the speedo needle not moving smoothly (in either direction, accelerating/decelerating). What the heck is this all about. Does this have to do anything with the computer learning process? Or is it another problem. The speedo wasn't acting funny when I started on the trip today (weird).

GREGGO, when you say get the electrical load up in step 2 can I just turn the AC, radio, and headlights on? I don't have a rear defroster but I'm sure that doesn't matter, but I just wanted to check.

 

Cool Greg.

From what I've noticed, I get a somewhat noticeable "wake up" on the fourth day after a fuel trim reset or reflash. It could be just the type of driving I do in relation to the above post.

It's odd. I reflashed last night after a VE table change. I scanned this morning, and saw some strange LTFT and STFT's. I did a FT reset while driving, and watched the LTFT's start to get influenced pretty quick - but they all looked normal. Nothing strange like before the reset. From what I saw there, it'll take a little longer for the LTFT's to be completely "sorted" unless you can do a full computer reset.

 

Thanks everybody for the help. I put on about 100 miles the night I asked this question (took a long freeway drive) and it worked. I took it back the next afternoon and it passed the smog check. Only the evap system hadn't been learned yet but the smog guy said it's something that didn't matter for the truck to pass the testing process. Well I'm happy now and the truck is SOLD! Now onto my next purchase/project