Resetting a chevy computer?

LastDetail

LastDetail

Whose yer DADDY!??!?!?!?!
Hey everybody!
I just changed out my battery and now the car is idling extremely rough. I was wondering if anyone knows how to reset the computer on an '01 Chevy Tahoe? From what a friend told me it is idling rough because of the battery change. Any help would be appreciated.
 
Typically just removing the ground on the battery for about 30 minutes will reset a computer. If that doesn't work then pull the ECU fuse and that will basically do the same thing. It should run rough for a little bit while the ECU relearns what the engine is doing, but then it smooths out. I'd give it a couple days before you reset it again.
 
When you disconnect the baterry for a few minutes it shoulld clear the computer. As far as trouble codes go. You could go to Autozone or Advance Auto and they can clear the trouble codes. I have never heard of problems that you describe from changing batteries. I know that on trouble codes that the computer can go into a failsafe mode if a sensor goes into a trouble code.
Some computers are supposed to learn some driving parameters, that should clear without electric supply.
 
Allright the negative is cable is off the battery and Im gonna let it chill for a little while before re-attaching.
Apparently the problem was after we swapped in the new battery it reset the computer, but nobody told me that I needed to drive it mild for a little while so the computer could re-learn whatever it needs to learn, so I just got on the freeway and pounded the pedal down and drove all the way home, (about an hour and a half) at 70-85 mph. Then when I got off the freeway the idle was horrible.
Hopefully this fixes it, I was thinking that it was the fuel pump.
Thanks for the quick responses guys.
 
Remove the negative (black) cable, and cut on the lights for at least 30 min.
Before anybody ask, cutting the lights on will take out any power in the system out.
 
Sparkie said:
Remove the negative (black) cable, and cut on the lights for at least 30 min.
Before anybody ask, cutting the lights on will take out any power in the system out.
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I could only see this if there is a capacitor in line. Some people with large
sound systems have these inline to handle system draws on peaks. Newer
cars do not use these and should not be affected. If you have them it might
be prudent to discharge or disconnect them for a reboot of the computer.
Be carefull about compacitors if you are unfamilar. They can be dangerous.
I learned this the hard way back when points were the norm. Touch it and
ouch, Where in the he double fiddle sticks did that come from.
 
belcherm58 said:
I could only see this if there is a capacitor in line. Some people with large
sound systems have these inline to handle system draws on peaks. Newer
cars do not use these and should not be affected. If you have them it might
be prudent to discharge or disconnect them for a reboot of the computer.
Be carefull about compacitors if you are unfamilar. They can be dangerous.
I learned this the hard way back when points were the norm. Touch it and
ouch, Where in the he double fiddle sticks did that come from.
Click to expand...

Oh man! I completely forgot about the Cap! I do have a 1 farad capacitor for my system and it is still connected in line. Maybe this is why the reset didn't work the first time! Thank you so much.
 
LastDetail said:
Oh man! I completely forgot about the Cap! I do have a 1 farad capacitor for my system and it is still connected in line. Maybe this is why the reset didn't work the first time! Thank you so much.
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Be carefull. You can eiather ground it out with the battery disconnected to the frame or disconnect the wires, both sides. I can't say this enough. You would not beleive what they can hold as far as current is concerned.
 
All I had to do is pull the fuses for the amps, they are before the cap in line. So fuses out now the system is %100 disconnected. Thanks for caring about my well being though! :howdy
 
LastDetail said:
All I had to do is pull the fuses for the amps, they are before the cap in line. So fuses out now the system is %100 disconnected. Thanks for caring about my well being though! :howdy
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That is from the up side. Disconnect one wire from the down side. Different people wire these in different. I did a lot of upscale sound installations at one time.
 
Also the ECM must relearn and it does that VERY slowly if you let it idel, it needs to be drievn about 30-50 miles before is has enought long term fuel trim saved
 
DKKNE said:
Also the ECM must relearn and it does that VERY slowly if you let it idel, it needs to be drievn about 30-50 miles before is has enought long term fuel trim saved
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All other things being equal (meaning you didn't knock a vacuum hose off etc.) this is the answer you are looking for. The computer has what's called a block learn function. It has to relearn your driving habits. Assuming you don't have a trouble code it should take care of the problem by doing nothing.
 
*update*
I reconnected the battery and left everything off - i.e. amps, head unit, air conditioning, fans, etc. - I started it up and drove about 30 minutes, driving pretty tame; for me. At stop lights it was very rough I kept thinking it was about to stall, then it would come back up to idle. Once it got through the rough spot at the bottom of the rpm it ran smoothly and I kept it around 35 mph with maybe a couple touches to 45. Never WOT (wide open throttle) or hard acceleration.
It is still idling rough though.
So you guys are saying that I should just drive it normally and that in a couple days this problem will just work itself out?
Thanks.

P.S. The response to this question has been just great, I put the same post on LS1Techdotcom and even though it got 8 or 9 views not a single person deigned to respond to such an apparently simple question. I love that nobody here is being an elitist auto guy and not getting down on me for not knowing very much about engine mechanics. :dcrules
 
How old are the spark plug wires? if its running rough to the point that its going to stall then its not the computer trying to learn something. I would test the plug wires if it doesn't smooth out in a few hours
 
harry444 said:
How old are the spark plug wires? if its running rough to the point that its going to stall then its not the computer trying to learn something. I would test the plug wires if it doesn't smooth out in a few hours
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You know its weird that you mentioned that. I just had (as in 3 days ago) my mechanic check the plugs and wires. He said that the wires were fine but that the plugs needed to be changed. I gave him the go-ahead and he changed out the spark plugs but used the original wires. This guy has never steered me wrong so I would imagine that the wires are fine. The only other thing that I can think it might be is the fuel pump. I am still on the original stock one at 107K.
Also my mechanic just did a full fuel system clean out, where he put an addititve in the fuel and a leak down through the intake manifold.
 
Fuel system clean out HMMMMMMM Fuel filter may be clogged... if it was the fuel pump your car wouldn't run at all in the old days the fuel pump ran off of your cam shaft today there electric so the chances of it being bad is slim to none next thing you can check is your fuel filter that would make your car run bad also check to see that the plug wires are on tightly around the spark plugs if one is not on corectly the car would be running rough big time
Good luck! keep looking you will find it ...:)
 
So I checked all the plugs, pressing them firmly at both ends, and now the check engine light is on. I think I might be doing more harm then good here. Sometimes I regret having never learned jack about motors.
 
DKKNE said:
Also the ECM must relearn and it does that VERY slowly if you let it idle, it needs to be driven about 30-50 miles before is has enough long term fuel trim saved
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this is the best advice I seen here yet....

Never disconnect a battery cable while the veh. is running... EVER. this is the fastest way to wipe out a PCM.
not sure if the 01's had 2 computers in them or not I do know that today there are as many as 3 systems on board. ECM, PCM and TCM.

with the caps on the larger sound systems you can discharge these by (engine Off)removing all power leads to the units and turning the unit on for a moment or two.

do as DKKNE stated first.... this is most important to relearn the computer before you move on to other problem... if you do to many thing you will end up chasing your tail,

relearn the computer first,
there are some veh that need to be driven at a constant speed for a period of time before a relearn will happen, stop and go traffic will only extend the time for the computer to relearn. if you are NOT throwing a "Check engine" light the system will reset sooner.

if the problem still occurs you might want to find someone with a good scan tool to look at the values the computer is seeing and trouble shoot from there.
 
OK so now I have checked all of the plugs and they seem to be making a good connection and the car is throwing a Service Enging Soon light. It is still idling rough, and it doesn't seem that I know anything about engines. Thanks for all the help guys, seriously from the bottom of my heart, but I think my limited knowledge is what is preventing me from properly fixing whatever is wrong. I guess I am just gonna take it back to my mechanic on monday. It just steams my clams that I just paid to have the tranny replaced, and the fuel system cleaned and the plugs changed and a new battery, yadda yadda A month of down time and it is STILL having problems.
But seriously your help is very very much appreciated especially Harry and Belcher who took time repeatedly to post in this thread trying to help me out.
 
Well too bad your on the west coast and not the east I would have checked it out for ya if you were close good luck I know its going to be something stupid like a fuel filter or a disconected sensor let us know what it was :howdy
 
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