mattandchris

I understand that by disconnecting + reconnecting the battery, I reset the ECU.

My question is;
Do I have to do an idle relearn everytime I disconnect+reconnect ?

Or, do I only do an idle relearn when I replace a part in the engine compartment? remove+clean+reinstall an electrical part? Spark plugs?
Serpentine belt? O2 sensors?

In other words, anything that would affect / increase the performance of the engine?

I'm going to replace that external transmission filter today and was wondering if that would require an idle relearn, by the mere fact that I am going to disconnect / reconnect the battery?

TY...in advance...........mattandchris......2010 Civic LX......30K

palsana

excellent question

ezone

Wow.
"No" for a lot of that.
Mostly only necessary when you do something that will affect the idle or the PCMs learned parameters (memory).
No on the filter.
No on plugs, belt, or O2 sensors. Not necessary.
Hell, it doesn't even say to do it when you disconnect the battery!



Here's some C&P from the Honda site under 2010:
The idle learn procedure must be done so the ECM/PCM can learn the engine idle characteristics.
Do the idle learn procedure whenever you do any of these actions:

• Replace the ECM/PCM
• Reset the ECM/PCM
• Update the ECM/PCM
• Replace or clean the throttle body
• Disassemble the engine or the transmission

NOTE: Erasing DTCs with the HDS does not require you to do the idle learn procedure.


(NOTE: "reset" is a different procedure from erasing codes with the HDS, but SOME code readers make the PCM do a "reset" when codes are cleared. IF you have idle issues, then do a relearn. "Update" means upload new software into the PCM, pretty much a dealer only thing.)

HTH

mattandchris

ezone............tyvm for your reply

My thinking was along the lines of a rough idiling car because of bad plugs.
Change the plugs/ the idle changes to something smoother/ idle relearn?

A rough idle because the filter is plugged up. Change the filter/ car idles smoother/ idle relearn?

O2 sensor causing screwed up air/fuel mixture. Rough idling engine/ change O2 sensor/ idle relearn?

I just bought this car and am trying to get higher on the learning curve by stalking this forum. Thanks for your time/help.

My parents had alot of trouble with woodpeckers on my head when I was a kid.......

mattandchris..........2010 Civic LX..........30K

ezone

The reality is that is isn't really needed very often.
If you have it running poorly, just how often would you leave it idling in the pattern necessary for the learning process to be enabled?
I'm guessing not very often. Therefore, it won't learn new idle parameters on a SNAFU running engine unless you do. Fix the bad running, it goes back to normal.

When I do have to do it, it seems like nothing to actually do it: get it warmed up, leave it idling and walk away for 10 minutes while I do something else.


You have a 10 with 30k.
I think you are worrying about the wrong things.
You have some warranty left.
You only need a trans service and oil changes and fix what's worn out.
Yeah, I still think the cars need far more ATF services than what the book or maintenance minder says. I'm replacing torque converters at 60-70k on some.
You won't need a belt or plugs until 100k or more, filters won't make it idle bad, and there are a slew of codes and fail-safes related to O2 sensors if one does happen to go bad. It isn't likely to run poorly because of it.

ezone

That's almost funnier than mine:
I wasn't just dropped on my head......I was HURLED repeatedly.

danwat12345

Well this is an interesting topic. I understand that no car is mechanically the same. All engines have slightly different amounts of compression, vacuum, internal friction, etc and the computer needs to correct for that.
But why does it need to learn this behavior? Can't the sensors immediately tell the computer if the RPM or A/F is off and will correct? RPM with I guess a crankshaft sensor and A/F With an 02 sensor and correcting by changing the injector behavior or modifying the IACV/butterfly valve.

It's called idle re-learn, so the computer does not use learnt (yes learnt) stuff for when the engine is above idle, why not? I guess because RPM isn't important, but A/F still is... I guess spark timing is not ever learned but just uses stock numbers, and with newer engines, CVV timing is stock and never learnt (well duh it's purely mechanical I think, but Advanced VTEC is electronic, though not out yet)?

Whenever I've disconnected my battery to do stuff with my car and left it disconnected for hours, finished my project and drove the car, I have never noticed any difference in the idle or driving. Maybe because my car has the ideal engine so it doesn't have to learn anything or it is immediately correcting with sensors until it learns? Maybe sensors and computer learning is intentional redundancy in case unideal crap happens like temporary bogus sensor readings, but again, "IDLE" re-learn only...?

What year of Civic started having an ECU that stored behavior? All OBD2 and newer, all cars in the US?

ezone

^^This.^^

Idle is a learned parameter ever since the cars went to OBD2. Most people don't have issues with it, but some do.
Fuel trim is constantly adjusted and learned. LTFT is a learned value.
CKP can be a learned value (crankshaft profile) on newer cars, both low resolution and high resolution. Misfire monitoring depends on these.
Throttle adaptation/learn on fly-by-wire cars. And more.
I'm not going to explain the rest of the questions right now. I need sleep LOL.


Your car is a 99?, there isn't much more than idle and LTFT on yours, but that's like dinosaur tech to me now.... I deal with cars up to 14 years newer than yours. (We just got our first batch of 2013 Accords this evening.)


When your car drops dead and/or you get a newer car, you will probably be overwhelmed with the same technology you are denying now, though you may not have to deal with any of it until there is a problem. Right now, just about everything with wires seems like it runs off of a computer somewhere.
And Honda has been behind the curve in many areas compared to other manufacturers for a long time, while leading in other areas.


ZZZzzzz

gearbox

iTrader: (95)

just my own experience....on my auto trans civic if i disconnect the battery and do not do the idle learn, i will have idle issues all the time. when i accelerate and let off the gas, the rpms jump around a few times and act weird. same when braking to a stop. the parked idle speed is off and sometimes has rumblings or hunting up and down. doing idle learn completely fixes all these issues.