beak

Resetting your ECU. Your ECU is your cars brain. It tells your engine what to do and how to do it based on tons of readings it recieves along with how much throttle is being applied and so on.

After you perform any modification to your car. You should reset your ecu so it can clear its memory and re-learn and adapt to the new parts. Instead of having it try to optimize in with its old parts. Its best to reset and let it learn from the new setup....instead of trying to get it to forget the old.

It can be easily done by unplugging the negative battery cable connection. If I remember correctly my chilton manual says 30 seconds. I still try to leave it off as long as possible. Into the night and possibly next morning if you can.

Then you connect the cable back on. Then start the car outside , let it run till its full warm. Normally 5-10minutes during the summer. Some wait till they hear the fan kick on....but you really just need to see the temp gauge at its normal operation position. Do not touch the gas pedal. Then once warmed.

Shut off and use when you are ready.

Also some like to take the car out and run it hard around 3times. Basically 1st through 3rd like you are racing. Of course this sounds kinda weird , I dont know if to believe this. But it cant hurt and it sounds logical , so it doesnt get some weak run and try to learn from that , you immediatly feed it some hard runs to set it self to and you should be good.

You also have to reset it for every mod. I also do it for every season change. This also lets your car adjust to the environment , different humidites and oxygen levels and densities. All are different variables that can effect your cars performance. So to take full advantage , you again want your car to learn and base its settings off a smaller period of time. So resetting it in lets say winter, its like its whole life was driven in the winter , and so on and so forth. Instead of having it try to adapt from its summer time conditions over to the winter...its best to just start fresh.

-- NOTE , do not try resetting your ecu when you have any sort of fuel additives or things in your car that you wouldnt normally have. So fuel cleaners , higher octane fuel , different fuel than you normally run...dont try this then.

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Don't fry bacon when you're naked.

96 EK Hatch 343whp, and 245ft/lb torque at 11psi - Stock GSR Motor

demigod

step 1: take your car for a brisk drive to get the motor to operating temperature.

step 2: take your car home, and take the fuse for the ecu out. it'll more times than not be labeled, but on civics and integras it's under the hood for sure. wait 15 minutes.

step 3: put the fuse back in.

step 4: turn the car on. DO NOT TOUCH ANYTHING. GIVE IT NO GAS. let the car idle for roughly 15 minutes, or until the car is idling smooth at lower rpm's.

step 5: turn the ignition off. ONCE AGAIN, DO NOT TOUCH ANYTHING OTHER THAN THE KEY. immediately turn the ignition back on after you have gone to full off. this will store the new settings your ecu has made.

These steps will properly reset your ecu. After they are accomplished go do whatever, the new settings have been stored.

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All Motor H22 Civic, stock internals.

12.61@107.56 on BFGs with highest MPH of 109.12

demigod

The ECU of your car is like its brain. For your car to deliver it’s best performance you have to keep it in a fit condition at all times. This is the only way to ensure that you get the best in both driving as well as handling. Modern day cars do not have manual controls. Nowadays sophisticated technology is being incorporated in the form of computerized controls that guide and ensure Engine performance. Whenever you make a physical intervention the data pertaining to such intervention gets recorded in the memory banks of your car’s computer. The computer uses the mapped data to work out the optimum control conditions in which the engine should function. The ECU shuffles through the tons of data that come to it in the form of readings to decide the course of action that should be taken by the engine to ensure an ideal drive. The ECU tells your engine not only what to do but also how to do it. Thus the ECU in order to make accurate diagnosis on engine control utilizes stored data.

Even though you have made modifications in your car, the ECU still continues to get an input of the old data which is stored in it’s memory. This old data no longer is credible as it pertains to conditions that existed before the modification. The input data to the ECU should pertain to the post modification situation of the components and parts introduced, while making the modification. This means that you have to erase the old data from memory and new data pertaining to post modification should be logged into the ECU memory by mapping in new readings. This is the reason why ECU resetting is essential for optimum performance after any modification has been carried out in your car. The moment you have carried out the modification you should purge out existing data in your ECU’s memory. You should then feed in fresh data pertaining to the conditions that have come into existence post modification. The ECU has to operate on the newly acquired data as this new data reflects the true conditions post modification.

You should be well versed with the vital art of resetting the ECU of your car. You have to let your ECU adapt itself to the new situation arising out of the modification. Allow your ECU to relearn and perform.

Now therefore the step to be performed is to purge the old data and reset your ECU. Doing this allows it to adapt itself to new parts and efficiently perform post modification also. To reset the ECU you simply have to unplug the negative battery cable connection. Theoretically it is best to leave it in this disconnected condition for as long as you can. Practically leaving it disconnected overnight is more than enough.

After having left the cable disconnected for sufficient time you have to connect back the cable. Start the car and keep it running so that it warms up. This would not take more than 10 minutes at the most in summers. Once you have done this you have accomplished the ECU resetting. Shut off the engine.

You can now use your car whenever you feel like. ECU resetting is over.

You should remember a few points when doing the ECU setting. One important point that you should remember is not to reset ECU when using fuel additives or different octane fuel than you normally use. The idea is not to reset the ECU when using anything in your car that you normally don’t use. You should prepare the ECU to get adapted only to the conditions that it would normally encounter. This would also reduce the number of resets you will have to do to the ECU.

However if you are going to change the operating conditions on medium or long-term basis then you should reset your ECU. One such instance could be when you think of boosting octane. Resetting the ECU when you choose to boost Octane becomes necessary because your ECU has a memory bank for octane. This means that if you've been using lower octane, the response of ECU will correspond to lower octane with the booster matching lower octane performance. The ECU response will continue to correspond to lower octane even though you have started using higher-octane fuel. This is because the ECU has not been reset for higher octane. Thus even though higher octane is in actual use, the data in ECU memory still corresponds to that of lower octane. This mismatch affects performance, as you are unable to derive the benefits of boosting the octane. Therefore you should reset your ECU periodically after filling up full tank in order to ensure that ECU adjustments for its octane memory are made afresh corresponding to the octane actually in use.

You can even customize resetting of your ECU so as to enable it to adapt itself to seasonal changes. Since humidity, air density, oxygen levels etc in air affect performance you could reset the ECU to adapt to these variables too. The advantage of such resetting made to your ECU is that your car performs the best in every climatic condition. This lends versatility to your car- and all this at no cost.

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All Motor H22 Civic, stock internals.

12.61@107.56 on BFGs with highest MPH of 109.12

demigod

The TechnoMotive ECU Theory Series
ECU Reset Definition

The ECU "learns" about your engine as you drive the car. The "learning" is actually a process that the ECU uses to track the tolerance changes of the sensors and actuators on the engine. Two examples of these values are the position of the idle-air bypass valve (automatic choke) at idle with the A/C on, and the trim gain on the injectors. The ECU stores these "learned" values in battery backed-up RAM so that it doesn't have to start from scratch the next time you turn your engine over.

"Resetting the ECU" is the process of clearing all the long term memory from the ECU's memory. These variables trim idle speed, fuel, spark, and more. The ECU will also store trouble codes for diagnostic capability. By resetting the ECU, the trim values will be set to some neutral default value and all of the trouble codes will be cleared.
How-To

To "reset" the ECU, all you have to do is remove the source of backup power. To keep the memory alive while the car is off, the ECU has a direct line, through a fuse, that goes right to the battery. This is usually the same line and fuse that supplies backup power to your radio so it doesn't forget all of its settings. In a DSM, this is the fuse that controls the footlights that go on when you open your car door. On a 1990-1994 DSM, this is the 10A fuse in the lower-right-hand-corner of the fuse box near the driver's footwell. On a 1995+ DSM, this is the 10A fuse on the right-hand side of the middle row of the same fuse box. Pull this fuse with the key out and wait for about 15 seconds, then put the fuse back in. Your ECU has now lost all of its long term memory values and will "reset" them all to defaults when it next powers on. By the way, the factory radio's memory lasts for a minute or two, so you probably will not lose your saved stations.

Sometimes people like to pull this fuse when they are working on or cleaning the interior of their car. This fuse also controls the lights that go on when you open the door, so many pull this fuse so they don't drain the battery during their job. However, this will also cut backup power to the ECU.
Myth

There is quite a bit of mythology revolving around resetting the ECU. Many people mistakenly believe that they need to reset the ECU after installing major engine modifications. Others believe resetting will resolve engine problems. Neither are correct.
Reality

The ECU is always tracking the engine's sensors and actuators. Resetting the ECU does not cause the ECU to learn engine changes any faster. The ECU is always tracking the gradual changes in the engine sensors and actuators. The ECU never gets satisfied with a setting, and is always updating the trim values. It will discover whatever change you made to your engine and make the appropriate changes. In fact, unplugging the ECU will most likely increase the learning curve of the new part.

On a DSM, there are only two reasons why you would want to reset your ECU. One is to clear a CHECK ENGINE light or error code after fixing the problem that caused the error. The other is to reset the spark advance trim value. The advance trim controls how much the timing is retarded from what the factory engineers considered optimum. This particular trim value is the only one the ECU "resets" to a non-neutral MAX value. If you are driving on low grade gas, the pinging picked up by the knock sensor causes this trim value to be lowered, and your timing to be retarded. If you go to the track and put good gas in the tank, you might not want to wait for the ECU to learn about the new gas and advance the timing. So resetting the ECU in this case makes sense. However, in the process, you will lose your idle and fuel trims (probably not too important for drag racing, though).
Questions

Won't clearing the trouble codes make the car run better? On a DSM, no. If the ECU notices a problem with a sensor, it will flag a code and possibly turn on the CHECK ENGINE light. Should the problem go away, the ECU will turn off the light and start using the sensor as normal once again. The code will be stored inside for later diagnostic retrieval. But that code being stored does not affect the ECU operation in any way.

I reset the ECU, and now the car runs rough! Why? The engine may run rough or idle poorly right after ECU reset. The ECU now has default numbers in its trim memory - it has to adjust them to match the tune of your engine and its sensors and actuators. It might take a day or two of driving in traffic before the engine will settle down again. Now you know why the ECU remembers these values in the first place!

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All Motor H22 Civic, stock internals.

12.61@107.56 on BFGs with highest MPH of 109.12