Reseting the ECU

[Jbeni96]

Can someone please explain to me how to reset the ECU on a 05' S2000. I am having an idle issue that someone said might be fixed by tapping on the Map Sensor and resetting the ECU. Thanks.

José

[ottokrat]

Resetting the ECU can be done by disconnecting the battery for a while. Most people say 15 min is enough, but I usually do it overnight when I want to reset the ECU (I'm sure it's overkill, but it is easy enough).

For some of the model years, there is a fuse that you can disconnect instead (I think its called "backup") but that went away, mabye in 06. (In the 06+, the ECU does diagnostics for 15 or so min after shutting off the ignition, so best not to mess with the car during that time.)

Map whack is usually not an issue for AP2s; I think that was a big issue only for the early AP1s.

Also for idle issues, check throttle body area right around where the throttle plate would be when its closed, to make sure it is clean and free of soot, deposits, or sludge.

You might also consider cleaning fuel injectors - have a service done, or, do it self: for that I like Chevron Techron Concentrate Fuel System Cleaner (not the ProGuard); it takes about 3/4 of a tank to work. After using it, I like to run one or two tanks of gas more (w/o any additive), then change the engine oil and reset the ECU.

There might also be some kind of Idle Air Control valve that can be cleaned, maybe someone else can comment.

[Jbeni96]

Thanks Otto. I appreciate the input. The idle problem normally occurs when I start the car up in the morning with a cold engine. It idles rough for a few seconds and stops. After that it's fine the rest of the day. I noticed that if I turn the key and wait a few seconds before pushing the button, it doesn't do it as bad.

José

[ottokrat]

That's interesting informatiion.

One thing that happens when you turn the key on is that the electric fuel pump starts pressurizing the fuel rail & injectors. (If you don't start the car, on most cars this pump will shut off after about 2 seconds, having brought the system up to full pressure.)

So, if there is a small pressure leak in the fuel system, this action of waiting with the pump on before starting can help. In a brand new car, the pressure will hold overnight and then some, so it is not necessary to wait before starting to have full pressure.

If it is a small pressure leak in the fuel system, that is probably a fuel injector that weeps a bit when it's off, which allows the fuel pressure to go down (and might let a bit of air in the fuel line too). Because your car runs fine after the first start of the day though, they can't be weeping very fast. One could live with it, using that start delay techinque, and, eventually, have the injectors replaced. In the mean time, cleaning them might help the problem, as a such a weep could possibly be caused by deposits (or could be caused by wear, in which case cleaning probably will not help).

You might try doubling the start delay as an experiment: turn the car on w/o starting, and after two or more seconds, then turn it off. Wait a bit (don't know how much, try different amounts, like 10-60 sec, maybe try like 30 min one time). Then turn it on again w/o starting, and wait at least two seconds, and then go ahead and start it.

Of course, it could always be something different... Best of luck!