low ideal after disconnecting battery

[DRBROOKSZ]

Quick story on what happened.---on vacation for one week, came home uncovered my 2003 nsx and the door is ajar and battery is completely drained. So i disconnect the battery cables from terminals and charge fully. Car starts right up an runs great--i come to a stop sign put the brake on --car dies--start up again come to another stop sign an idle drops --car dies==whats up--is the ecu effected? I'll drive it again tomorrow and see what happens--any ideas? Thanks-drbrooksz

 

[ftuhy]

Definitely weird. Considering cranking the engine takes hundreds of amps, its highly unlikely its the battery. And if the alternator was bad, the battery would easily sustain the load from the brake lights, etc because it is able to re-start the car.

I think you may be correctly suspecting the ECU. Now that the battery is fully charged, I would removed the clock fuse for a few minutes to force a reset of the ECU. That might at least clear out any "confused" settings. Then start the car and do a variety of driving (warm up, then some quick acceleration, some driving at highways speeds, etc) to re-train the ECU.

Hope that helps.

 

[Larry Bastanza]

Quick story on what happened.---on vacation for one week, came home uncovered my 2003 nsx and the door is ajar and battery is completely drained. So i disconnect the battery cables from terminals and charge fully. Car starts right up an runs great--i come to a stop sign put the brake on --car dies--start up again come to another stop sign an idle drops --car dies==whats up--is the ecu effected? I'll drive it again tomorrow and see what happens--any ideas? Thanks-drbrooksz

This actually is not wierd. Your car has a DBW throttle (Drive By Wire). The ECU "learns" the throttle position. There is a procedure in the 1995+ service manual that describes how to teach it. You need to install the OBD "Test Jumper" in the blue connector under the glove box, and then start the car and idle it at 1000 rpm for a minute or so. Should return to normal.

I recommend reviewing the service manual for details.

HTH,
LarryB

 

[ftuhy]

Larry,

Some PITA curiousity questions.:biggrin::biggrin:

I figured the problem came from low battery voltage putting the ECU in a somewhat random state, and that re-setting the ECU would probably help.

What's interesting, there is no reference in the manual to doing this after a battery replacement. (However, once I knew where to look, I did see the section on re-setting the DBW idle speed.)

1. Was it just "luck" that this happened to DRBROOKSZ, or is it a "normal abnormality" with a total battery discharge or whenever the battery is disconnected or replaced?

2. Once it happens, would it eventually clear with the ECU re-set and re-train via some driving as I suggested? Or, is the only cure to follow that specific DBW idle speed re-set proceedure?

 

[Larry Bastanza]

Hi Frank,

It seems that once you disconnect the battery it is the same as removing the clock fuse, the ECU gets reset and it needs to learn all over again. But here is the strange part: not all the time. Because I always disconnect the battery for any service, and I have done many 1995+ cars. Typically I do not have to go through this procedure, but we had this same issue with DocJohn's car, and this was the way to get the idle correct.

John's car was stalling all the time and the reset procedure was the only thing that fixed it. Subsequesntly, at Kid's Day John had a check light is I decided to reset it once I read the code. Darn thing would not idle worth a damn after that, and needed the procedure again.

With that said, I cannot explain why a certian car may "lose it's brains" vs. another car I do a service on then reconnect the battery and all is fine.

That is one for the Honda engineers to answer.

Regards,
LarryB

 

[DRBROOKSZ]

Thanks guys for your feedback--i tried pulling the fuse and disconnecting the battery again, also tried holding at 1000 rpm for a few minutes----no success----next week i'll call john martin at cerritos acura--- let you know what happens. Drbrooksz

 

[ftuhy]

Larry,

So now I fully understand your "fun time" at Kid's Day on DocJohn's car. You were mumbling enough bad words at the car that I left you alone.:biggrin:

DRBROOKSZ,

I don't at all mean to be condescending, because getting a step out of order can halt the re-train procedure. So, take a deep breath then, as Larry noted in his first response, (once again) read the manual carefully on this procedure. Its probably worth one more try.


If that doesn't work, let us know what the dealer finds. That's how we keep building the "experience library".

 

[DRBROOKSZ]

Well i called john martin at Cerritos Acura ---- he said this will happen to the newer NSX when the battery is drained for a long period of time. He said it's electronic control, he had me start & idle for 10 minutes ---it worked --- thanks again for your help-- Lance