ECU Reset, when and why?!

[amirh]

Question for you guys(and gals)
When do you need to reset ECU? I am not getting good MPG, should I try reseting ECU?

Thanks,
Amir

[airportguy770]

you can try, all it does "brain wash" your car, after 90 miles or so it will re-learn everything. How many miles on your car, I have approx 22K on mine and startting getting bad MPG. I cleaned my airfilter, checked tire pressure and ran a bottle of fuel injector cleaner through. I MPG went back to "normal." Also, try getting a lighter right foot. That always kills my MPG.

[amirh]

Originally Posted by airportguy770

you can try, all it does "brain wash" your car, after 90 miles or so it will re-learn everything. How many miles on your car, I have approx 22K on mine and startting getting bad MPG. I cleaned my airfilter, checked tire pressure and ran a bottle of fuel injector cleaner through. I MPG went back to "normal." Also, try getting a lighter right foot. That always kills my MPG.

I have 800 miles on my car .
Can you tell me how to reset my ECU? Can I do it in my garage or I should take the car to dealer?
Thanks
Amir

[airportguy770]

Just unplug your battery for a couple of minutes that should do that trick.

[CaliGuy]

Usually people reset the ECU to get the CEL (Check Engine Light) to go off when installing aftermarket parts. Or to get the car to "learn" a new aftermarket part. You can try it to get better MPG but I doubt it will help (can't hurt though). Just disconnect the battery for 20 minutes or so and ECU will reset...

[Yodums]

What they said. Generally you want to reset the ECU after installing aftermarket parts, so it can apply settings that are suitable to the new setup.

[catchx34]

Originally Posted by Yodums

What they said. Generally you want to reset the ECU after installing aftermarket parts, so it can apply settings that are suitable to the new setup.

what happens if you dont reset it? I remembered taking my battery off when installing the SRI but didnt disconnect it after i started it up.

[si_civic]

If you don't reset periodically, it'll keep in memory your dirty filter, injectors, etc etc. This is why it is important to reset your ECU after every oil change when you change your filter, or every time you add a performance part, OR after a certain amount of miles.

My .02

[dannn]

Originally Posted by si_civic

If you don't reset periodically, it'll keep in memory your dirty filter, injectors, etc etc. This is why it is important to reset your ECU after every oil change when you change your filter, or every time you add a performance part, OR after a certain amount of miles.

My .02

not true
the ecu does not have to be reset for those reasons.
basically what you do when you reset the ecu is reset the long term fuel trim and any other settings stored in the KAM (keep alive memory).

long term fuel trim is changed based on what the short term fuel trim wants to do. when you change something like an intake the stored settings will not work the way the ecu wants with the new part.
so the short term will start to compensate. if the short term cannot compensate enough the long term with change to allow short term to do its job.

long term fuel trims are used to compensate for wear that happens on the engine. things such as fuel filters flowing less over time, air filters getting dirty etc..

lets say the ecu got used to the clogged air filter. when you replace or clean it the settings used for the clogged filter wont work as well so the ecu will self adjust to the freer flowing filter.

the ecu will "reset" itself, no need to do it manually for maintinence reasons.

the only time i would reset the ecu is for diagnosis
also if you reset the ecu you will most likely reset your ODBII trip monitors and wont be able to pass smog.

[abs0lutexer0]

Originally Posted by dannn

also if you reset the ecu you will most likely reset your ODBII trip monitors and wont be able to pass smog.

So resetting the ecu will prevent you from passing smog??? How is that possible???

[dannn]

Originally Posted by abs0lutexer0

So resetting the ecu will prevent you from passing smog??? How is that possible???

my post explains it
your obdII monitors would not be completed
the machine at the smog place wont allow your car to be tested when its hooked up to the obd port.

[airportguy770]

Originally Posted by dannn

my post explains it
your obdII monitors would not be completed
the machine at the smog place wont allow your car to be tested when its hooked up to the obd port.

Thats not true. When you reset the ECU it will clear any trouble codes in the computer thinking the car is running properly. The codes wont come back for another 60-90 miles. I've had to pass a few cars through our emmisions systems down here in GA like that. I know here in GA thats all they really look for. To see if there are any trouble codes in the computer.

[abs0lutexer0]

Let's say if the car is completely stock (I mean there's no point to reset the ecu, but I'm just using it as if it were the case). So you reset the ecu for the hell of it. And just by resetting the ecu and this is w/o any aftermarket parts, you won't pass smog? Please educate me.

[dannn]

odbii systems run certain tests when the conditions permit.
such as evap and egr.
these tests happen in the background and the driver will not know they are happening.
if these tests are shown as not being completed the smog machine will not allow you to continue.

not all codes will clear by resetting the ecu
codes will come back if the fault it currently present. not after a certian amount of miles.

[CaliGuy]

Originally Posted by abs0lutexer0

Let's say if the car is completely stock (I mean there's no point to reset the ecu, but I'm just using it as if it were the case). So you reset the ecu for the hell of it. And just by resetting the ecu and this is w/o any aftermarket parts, you won't pass smog? Please educate me.

RESETTING THE ECU WILL NOT CAUSE YOU TO FAIL A SMOG TEST

I know this from experience...I've reset my ecu of prior cars many times and passed.

[CaliGuy]

Originally Posted by dannn

odbii systems run certain tests when the conditions permit.
such as evap and egr.
these tests happen in the background and the driver will not know they are happening.
if these tests are shown as not being completed the smog machine will not allow you to continue.

not all codes will clear by resetting the ecu
codes will come back if the fault it currently present. not after a certian amount of miles.

Where's the BS flag? Dude, here in Cali they don;t hook up to the ECU. They just stick in the sniffer, put you on the dyno and thats it. As long as the cel is not on thats all that matters as far as the ecu

[dannn]

Originally Posted by CaliGuy

Where's the BS flag? Dude, here in Cali they don;t hook up to the ECU. They just stick in the sniffer, put you on the dyno and thats it. As long as the cel is not on thats all that matters as far as the ecu

you do hook up to the odb port
we tried it with the machine
it wont even dial to the bar computer