So, we finally got around to installing the K&N intake last night...presumably followed instructions exactly, no little parts left over etc...took it for a 10 mile little drive and all was well.

Today I went for a slightly longer trip and when I pulled up back in the driveway, noticed the check engine light came on....hmmm. Aside from a tad bit more engine noise under acceleration, it seems to be running just as before with no problems.

Is the light from an error in installation, the computer not adjusting to more O2, a MAF issue...all of the above, none of the above, how are you supposed to know you aren't psychics....I have not taken it to have the code read yet as I just noticed it and won't have time to until tomorrow anyway.

Thoughts?

 

The computer may have noticed a change and is alerting you to what it thinks may be an issue. Retrace your steps to make sure your sensors are in place and plugged in properly. Also, disconnect the battery terminals and let them sit for at least five minutes. Before reconnecting them, touch them together, make sure they are NOT in contact with the battery posts!
This resets your PC and it will re learn the new configuration after start up. If the light comes on again, take it to a parts place like Pep boys or Auto zone and have them run a free code check. Check those code with the forum and you may find your answer.

 

That's an old wives' tail about disconnecting the battery to reset the computer. You have to go back to 1994/95 for a disconnect of the battery to reset anything.

Current flashed based data storage is not dependant on power to save data, and GMs save the last 300 start cycles (that is the start of the motor up to normal operating temperature, then until it is shut off).... even if you "clear the code" at the auto parts.

Now, if you are getting a short, or sending the wrong voltage to the PCM, a disconnect may diagnose that, or possibly cure the component creating the voltage issue.

If you are getting a CEL from an intake, 98% of the time it is because of a leak, pipes/hoses not coupled together correctly, loose clamp or MAF connecter. Double check your instal work, make sure all clamps are snug and the MAF connector is snapped on all the way.

Good luck. Email K&N and see what their customer service has to say.

 

Thanks for the informative responses, guys. I'll check everything mentioned here and if I still get a warning light I'll go get the code read then call K&N for their take.

Thanks again.

 

Doc, I wouldn't argue a bit concerning an actual full reset. Some newer Dodge diesel trucks can loose data this way, but as you wrote, normally only older trucks and cars. The post wasn't meant to instruct on how to hide, lose, or delete data from the PC, only to have it register a different input sooner. I'm sure you have put in your fair share of exhausts, engine mods, and air intakes. Most manufactures suggest disconnecting the battery for more than just liability issues I suppose. There sometimes seems to be a learning curve with the PC when some mods are made. While the PC will not "forget" what it has learned, it can correctly adjust to new data. Sometimes it only takes a good three or four times starting and driving a few miles to correct a code fix, changed adjustments, or read replacement parts. Leaving the battery disconnected during engine work is not only safe, but tends to force the PC to recheck input as a hard reboot of sorts. At least thats the best way I can describe it since technically the PC doesn't contain a functional HD.

The Hummer line is only about a year or more new to us. So I would definitely take your word over others in my shop. We have however been through more Jeep Cherokees than I would like to admit. While the Standard and sport models have always been good to us. The Grand Cherokee always was, and always will be a nightmare from way back. Especially when dealing with the computer! Sometimes unplugging the darned things and leaving them sit overnight, was the only way to get one to start properly after engine mods, lift kits, and tires packages were installed. And it was definitely the only way that stupid center dash readout would quit with the flashing!

 

Same thing happened to me after k&n cai install... took it to the dealer and the code came out to my engine running to lean, which I think means its not getting enough gas. They reset the computer, two days later the light was back on... eventually turned off then back on a week later, then off a few days later... its been off ever since. I read somewhere on the forum that the engine is trying to adjust to the new oxygen to fuel mixture and thats what causes the light to come on... although I could be wrong.

 

OK....these are the things that worry me ...I just ordered the catback and was about to order the AirDoc or do the Intake shown on the forum....BUT..I really didn't just spend almost 20 grand for a Rig and want the check engine light going on and off...I had also planned on doing the PCM ...but the website says complete the payment option and then we will ask you question and builded you a PCM... what does that Mean???
I would really like to do some MODs because I plan on using my H3 to tow my trailer..But I'm just Skeptical and worried on what to do...Mike

 

I Installed the k&n first, magnaflow catback second, airdoc third and had a PCM tune without any problems with my check engine light going off. At PCM forless after you pay you get a form to fill out asking questions on how you want your new PCM programmed (shift points, type of gas you use, etc.). They are very helpful if you have any questions, so between them and help from everyone on this forum, you should't have any major issues that can't be fixed pretty easily.

 

Follow Motley's lead. If your are a bit nervous, just proceed with one mod at a time. If you for some reason get a check engine light, you would then have a better idea where it may have come from, versus doing all the mods the same day or two.

However, please understand, and do so by looking at what Brick was saying back there...that a light on the dash does not mean you have a problem, it means you "may have" a problem.... look at me...... If the truck is running smoothly, idles properly, starts fine, a light is an indication your PCM has sensed a "new" condition outside of what it is programmed and learned to expect. A CEL showing up a couple times and then never comming back is not a bad thing, but rather an indication that your PCM learned the new condition and now understands it ..so to speak.

I am aware that more than a handfull of the K&N CAIs for the H3 and GMT 355s (Colorado/Canyons) have thrown a CEL for a lean condition, a couple freaked and returned the product, the rest went away some time later, or had the auto parts place clear it for them. This does not make the K&N CAIs a bad product.

If you get a PCM tune.... they program it to expect the extra air flow of an intake and know what to do with it, IMHO making it less likely a CEL will kick with an Intake and CAT back.

We have never been able to identify a CEL from an AirDoc Install ... yet.

 

When we installed the exhaust, we diconnected the battery per Magnaflow instructions. Installed the Air intake, Catback exhaust, And Jet performance chip all at the same time. We never had an issue with the engine light whatsoever. Some folks are not so lucky, but I have never heard of serious issues yet, or read them one on this forum that couldn't be figured out quickly.