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Discussion Starter #1
I need to know if the ECU resets itself when you disconnect the battery. I have a 2000 Civic DX Coupe.

Also, does anyone know what the current output of a stock alternator with stock pulleys is at idle?

I just had my car at the honda dealership today to have them check a stalling problem I am having (have not had it since I last had the car in for service), and they are saying that it is due to the AEM underdrive pulleys I have on the car. I have had the pulleys on the car since last april, and no problems...ever.

About a month and a half ago, the car started stalling, my alarm started acting real wierd, and the clock on my car stereo was slow (CDX-C90). This lead me to believe that the battery was having issues. Sure enough, the battery had a bad cell.

They switched the battery, but the problem was still there, the car ran like crap that day. They told me that it was because I had put high octane gas in the car (YEAH...thats it)

Problem seemed to subside, but I wanted to get the stalling issue checked, so I took it back in. They diagnosed the car and told me that it was the AEM Cold Air Intake on the car that was causing the problem. So, I then took it to another honda dealership to get the car looked at.

They are telling me that it is the underdrive pulleys causing the problem. I think that it was initially the battery with the bad cell causing the problems, and all the other problems are just because the ECU keeps getting reset.

Any suggestions?

1fast2dr

Sorry for the novel..I needed to vent since I got charged $100 today for them to tell me its the pulleys (my car is under warranty by the way)
 

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Yes the ECU does reset when the battery is disconnected, but only if it is left off for about 20 or so minutes. If you don't think it is the pulleys, then put the stock ones back on (if you still have them) and see if the problem continues. Anyway Honda dealers like to blame other aftermarket parts on the cars when they see them, just because it gets them out of fixing any warrenty problems.
 

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I never understood why anyone would think that it takes so long for the ECU to reset.

Technically speaking, I think it is a myth for the ECU to take so long to reset. There is no back-up battery to hold the memory in the ECU (since the programming is the same kind of firmware as any computer BIOS). Any changes made in the ECU are stored in EPROM. Once the power is turned off, the ECU should lose all it's settings that it keeps. Ever had a TI graphing calculator? If you didnt have that backup battery, all the memory would be lost if u had to replace the main batteries.

The only possible way for the ECU to retain it's memory after a power loss would be for a slow discharge from a capacitor or a couple of capacitors. But even if it did have any, it wouldnt last for more than a few seconds. An old radio would do that.

So I'd say, disconnect it for a few minutes and it should reset to its default state and it'll pick up and "reprogram" itself with the information from the sensors after the power is connected. Make sure to leave the car idle for at least 5 to 10 minutes for the ECU to properly pick all the correct sensor information.
 

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Discussion Starter #4
Thanks a bunch

Thanks for the info guys...I was pretty sure that the ECU would reset, but I wanted confirmation..

Appreciate it...

1fast2dr
 

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take off the negative terminal for 10-15 mins, then put it back on, start up the car. let it idle without touching the gas for 10 minutes, turn it off then back on and drive for 10 minutes then you just reset the ecu. but with obd II you don't even need to really reset the ecu, if it detects more air it automatically teaches itself new fuel maps kinda nifty.
 

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CiVTEC said:
I never understood why anyone would think that it takes so long for the ECU to reset.

Technically speaking, I think it is a myth for the ECU to take so long to reset. There is no back-up battery to hold the memory in the ECU (since the programming is the same kind of firmware as any computer BIOS). Any changes made in the ECU are stored in EPROM. Once the power is turned off, the ECU should lose all it's settings that it keeps. Ever had a TI graphing calculator? If you didnt have that backup battery, all the memory would be lost if u had to replace the main batteries.

The only possible way for the ECU to retain it's memory after a power loss would be for a slow discharge from a capacitor or a couple of capacitors. But even if it did have any, it wouldnt last for more than a few seconds. An old radio would do that.

So I'd say, disconnect it for a few minutes and it should reset to its default state and it'll pick up and "reprogram" itself with the information from the sensors after the power is connected. Make sure to leave the car idle for at least 5 to 10 minutes for the ECU to properly pick all the correct sensor information.
Usually I would say 15 minutes but I like to make sure it is reset right. And you do have to wait for 15 or so minutes, I have a manual and it states to remove power to the ECU for 15-20 minutes!
 

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I was just looking at an EPROM manual and it does say it retains it's memory even after it loses power for about 5-10 minutes. After that time, all of it is lost. So I guess I may be wrong!

I still think that technically speaking, it wouldnt make a difference because the new numbers are recalculated and mapped again after a modification.
 
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