Rep Power: 0

I will be replacing the battery in my 2001 Civic EX in a few days. This is the first replacement. It looks like a straight forward procedure. However, after reading in the Haynes manual, it sounds like it might not be. The manual says that after replacing the battery, the PCM has to re-learn the correct idle. The procedure says to start the engine, bring it up to 3000 rpm's, and hold it there until either the cooling fan starts or the coolant temperature sensor reads 194 degrees. Then you are supposed to let it idle for 5 minutes. I am wondering if doing this procedure is absolutely necessary, thinking that maybe the PCM will re-learn the idle itself after having been driven for a while. Does anyone have any experience on this?

 
Rep Power: 329

Do you "Have to do it" NO
Is is recommended that you do it. YES.

I have replaced the battery in my car a few times. I have not done this.

If you have the OEM radio you WILL need the code to turn it back on.

 
Rep Power: 254

Yea, if you dont want to it will just relearn on its own its really not that serious.

 
Rep Power: 0

Thanks for your reply. I have the radio that came as standard equip. Where do I find the code and what is the procedure to turn it back on?

 
Rep Power: 254

You may have to get it at the dealer free of charge. Once you get it write it down and dont lose it. Someone on here may be able to help you if you put up the serial number on your radio or your VIN number. Once you get the code your simply start your car and enter the number and put your presets back. Simple as pie.

 
Rep Power: 812

just goto walmart and get a "memory saver" for $5 which is a cig lighter socket and a 9v battery attached to it. plug that in, turn the ignition to ACC position to energize the socket, then change the battery carefully. the 9v will keep all your radio settings and ecu settings intact so you dont have to worry about idle learn and all that crap.

 
Rep Power: 0

can anything bad happen by not doing this? ive changed or disconnected my battery in my 01 a few times and my 05 multiple times and have never done this nor did i know you were supposed too.

 
Rep Power: 254

nope nothing can happen, your car eventually relearns after so many key cycles. I never do it either to be honest.

 
Rep Power: 812

my idle never learns by itself. i will always have jumpy rpm when letting off the gas unless i do the learn procedure every time. i think its mainly a problem for auto trans.

 
Rep Power: 308

Are you talking about the RPMs dropping down low and then bouncing back up somewhat when you let off the gas from a normal city cruising speed ??

I have noticed my 05 does this quite a bit. Not everytime though but a lot.

Also the idle just gets so low when it is hot outside (no stalling or bogging, just a very low idle speed)

 
Rep Power: 812

yeah exactly that. like you accelerate to a certain speed, let off the gas, and then notice weird things like the rpm isnt where it should be but then it recovers. doing the idle learn always fixes it. about the low idle, i havent noticed, altho i think 650 rpms is still within spec. ive never had the idle drop low enough to affect the idle or stall.

 
Rep Power: 308

Thanks for the reply, I need to clean & tighten my terminals, I may go ahead and do that and perform the idle learn afterwards.

 
Rep Power: 277

Wow, didn't know about this. I unhook my battery at least once a week to work on the wiring. And I swapped out my battery earlier this year.

 
Rep Power: 812

thats really bad because you lose all your fuel trims too. then the ecu has to relearn everything as you drive, and that could take upto a full tank of gas. otherwise you will never be getting the mpg or power youre supposed to.