Ecu Function

[hatharasinghe]

Dear All,

Is there any effect when disconnect or removing Battery to the ECU unit will it effect to fuel economy as I went to do smoke test at Kiribathgoda Eco and the Manager told if Battery remove or disconnect without giving external supply then ECU loss its data and nextime it may not functioning properly to optimize Fuel economy until vehicle drive at higher speed at least 100kmph then it again self calibrated is this true as i seen when at garages disconnect the battery and even if Engine light display at dashboard to off disconnect and re connect the battery so will it effect to ECU pls update me .Thanks .

[Ripper]

to put in simple word an ECU "learns" a bit of your driving habits and apply that to how it runs the car.

if the present "learnings" of the ecu is for somebody with heavy right foot...it will running the engine more towards performance over economy.

resetting the ecu by disconnecting power supply to it will erase those learnings and it will be running on factory defaults once you fire it up again.

after this the car might run a bit off for a while until the ecu learns how you drive the car... economy driving or performance driving

but in my experience...ecu re-setting wont improve economy drastically cos most of the time... bad fuel efficiency is linked to so many other factors.

[Dinuk]

Yes, Ripper is right... And I also dont think a fault hat failed the vehicle from the emission test won't be corrected by ECU resetting. (You haven't mentioned about a emission test fail...) An ECU always try to use a closed loop to control the fuel delivery. Unless the ECU running on safe mode or at several engine situations, such as cold start or full load conditions, the efficiency is maintained at highest level. performance vice it may have a effect....

And another thing... high performance means low economy..... resetting ECU and driving economically will reduce your fuel cost..... but I'm sure that will not be a large measurable figure....

[Ek3 Ferio]

to put in simple word an ECU "learns" a bit of your driving habits and apply that to how it runs the car.

if the present "learnings" of the ecu is for somebody with heavy right foot...it will running the engine more towards performance over economy.

resetting the ecu by disconnecting power supply to it will erase those learnings and it will be running on factory defaults once you fire it up again.

after this the car might run a bit off for a while until the ecu learns how you drive the car... economy driving or performance driving

but in my experience...ecu re-setting wont improve economy drastically cos most of the time... bad fuel efficiency is linked to so many other factors.

Hello ripper, will ECU gets reset as soon as we disconnect the battery wires or does it need to keep some hours with out battery power to reset?

Please explain.

Many Thanks

[Ripper]

Hello ripper, will ECU gets reset as soon as we disconnect the battery wires or does it need to keep some hours with out battery power to reset?

Please explain.

Many Thanks

well the ecu doesn't have an in built power source. at least not the ones i've seen so some settings will get erased after power supply gets cut off.

i'm not sure the exact time frame it takes and that too might differ from model to model.

The only time i did this...i kep the battery disconnected overnight.

[civicferio]

Hello ripper, will ECU gets reset as soon as we disconnect the battery wires or does it need to keep some hours with out battery power to reset?

Please explain.

Many Thanks

Following document explain how to reset the ECM of a EK3

[asanka424]

well the ecu doesn't have an in built power source. at least not the ones i've seen so some settings will get erased after power supply gets cut off.

i'm not sure the exact time frame it takes and that too might differ from model to model.

The only time i did this...i kep the battery disconnected overnight.

Even we unplug battery cables the charged capacitors in the ECU will remain charged and will hold up the memory for sometime. Therefore you need to wait until the capacitors discharge. Some say you can do in instantly after disconnecting the battery and then pressing break paddle few times. Since break lights are controlled by ECU it will waist the remaining charge of the capacitors by consuming it at the ECU. This does not mean that ECU will try to light up the break lights from capacitors but it will drain the capacitors by taking their charge to operate ECU itself.

I am not 100% sure but it worked on my car.

Thanks.

[Ek3 Ferio]

Even we unplug battery cables the charged capacitors in the ECU will remain charged and will hold up the memory for sometime. Therefore you need to wait until the capacitors discharge. Some say you can do in instantly after disconnecting the battery and then pressing break paddle few times. Since break lights are controlled by ECU it will waist the remaining charge of the capacitors by consuming it at the ECU. This does not mean that ECU will try to light up the break lights from capacitors but it will drain the capacitors by taking their charge to operate ECU itself.

I am not 100% sure but it worked on my car.

Thanks.

How do you get to know that ECU was reset in your car? And what is the car?

[hatharasinghe]

Deal all thanks lot u all update me greatly

[asanka424]

How do you get to know that ECU was reset in your car? And what is the car?

Error codes stored in the ecu were not there after the reset. car was hyundai elantra.

[fonfe]

to avoid having to wait long periods for remaing charge that left in the ecu a "hard reset can be carried out" this is meerly joing both battery leads once dissconected for 2-3 mins. this causes the power to be shorted in a way but because its such little power it does no harm.

i would not reccomend this as a means for fault clearing though, it does work on some models for that purpose but isnt good practice to do so.

but i would not be worried as in short the manager is making you worry over nothing. you do NOT need to drive at 100kph for an ecu to learn. a simple 10min drive to the shops and back is usually enough for most cars, but the saving in fuel economy is going to be so minimal that if for what ever reason you have to remove the car battery, just get in the car when you next need to go somewhere and dont worry about it.

you wont notice a thing different as the ecu is constantly changing fuel and igniton tables depending what demands are placed apon the engine. an ecu is not just one default running setting, it releys on its sensors to adjust the fuel and ignition accordingly especially the o2/lambda and knock sensors.

easy example of this is today where i was it was chucking down with rain, not a very hot day....so the ecu will alter for this, tomorrow it may be baking hot and no rain so again the ecu will adjust for this because the inlet air temperature will be far greater than it was today, also there will be less humidity so the engine cant run with as fast an ignition table as it could today.

aka its allways changing

[Kavvz]

Some say you can do in instantly after disconnecting the battery and then pressing break paddle few times. Since break lights are controlled by ECU it will waist the remaining charge of the capacitors by consuming it at the ECU.

I am not 100% sure but it worked on my car.

Thanks.

I've done it that way, and it works. (Reseting the ECU: Do this by removing the battery terminals and pumping your brakes 3-5 times to drain the current from the electrical system- be warned though that unplugging the battery is going reset everything electrical in the car including your clock, radio presets, trip data, etc. so things will be a bit weird for a day or two.)

[Kavvz]

Dear All,

Is there any effect when disconnect or removing Battery to the ECU unit will it effect to fuel economy as I went to do smoke test at Kiribathgoda Eco and the Manager told if Battery remove or disconnect without giving external supply then ECU loss its data and nextime it may not functioning properly to optimize Fuel economy until vehicle drive at higher speed at least 100kmph then it again self calibrated is this true as i seen when at garages disconnect the battery and even if Engine light display at dashboard to off disconnect and re connect the battery so will it effect to ECU pls update me .Thanks .

Partly true.

As 'Ripper' stated, resetting the ECU will cause the ECU goes into a default setting. From this baseline setting it will try and recognize how you drive and recalibrate itself to your driving patterns. Driving conservatively means it will align itself with a conservative profile that leans towards fuel economy rather than torque. Driving aggressively will cause the car to go into a 'sport' mode where the ECU will calibrate the engine settings so as to provide more torque (pulling power) to be available- unfortunately this does cause the car to consume more fuel.

As the outlet manager told you, resetting the ECU triggers this process of 'learning your driving habits' that the ECU is capable of. Where he was mistaken is that: As 'fonfe' mentioned the ECU is always monitoring various sensors and constantly changing your cars settings as it tries to optimize the car's performance. Therefore as pointed out by 'fonfe' it doesn't take much for the ECU to notice your change in driving and shift between a 'economical / conservative' mode and a 'sport' mode/setting/profile.

The ECU will in fact alternate between the 'conservative' and 'sport' settings on its own, based on your driving. If you drive conservatively comparatively more that you drive aggressively it should, without you having to reset it, chose to stay in the 'conservative' or 'economy' mode and vice-versa. Resetting the ECU is a short cut to speeding this process up- think of it like hard rebooting your PC instead of patiently waiting till the hour-glass icon does it stuff and stops flipping and turning.

How quickly the ECU changes between a 'economical / conservative' mode and a 'sport' mode/setting/profile depends on your car. More sophisticated cars will have more elaborate monitoring and adaptation to driver habits and switch faster between the modes. In more sophisticated cars features such as adaptive dampening (adaptive suspension), adaptive steering based on vehicle speed, traction / anti-skid control, turbo activation, variable valve timing, variable cylinder management etc. will all come into play during the 'sport' mode the 'economy' mode (and in-between-modes) to change the characteristics of the car dramatically between each setting.

If you want to see the change in ECU profiles and you have an automatic transmission its relatively easy to experience. Go ahead reset the ECU by disconnecting the car battery and pumping brake pedal 3-5 times. Upon a successful reset you'll see a marked difference in transmission shifts. For the first couple of shifts the transmission might even be a bit awkward and not as smooth as usual, causing you to think something's wrong with it. By driving around conservatively for five or ten minutes or so you'll see that the transmission will smoothen out and start shifting much lower than what it started out at. Keep driving like this and the car will stay in its economy / conservative mode. How quickly it will shift between 'conservative' to 'sport' and any other 'in between modes / profiles' is as mentioned specific to the car.

Edited November 2, 2011 by Kavvz

[Kavvz]

Dear All, Is there any effect when disconnect or removing Battery to the ECU unit will it effect to fuel economy as I went to do smoke test at Kiribathgoda Eco and the Manager told if Battery remove or disconnect without giving external supply then ECU loss its data and nextime it may not functioning properly to optimize Fuel economy until vehicle drive at higher speed at least 100kmph then it again self calibrated is this true as i seen when at garages disconnect the battery and even if Engine light display at dashboard to off disconnect and re connect the battery so will it effect to ECU pls update me .Thanks .

The manager may have been referring to something else completely. Did you fail your E-test (smoke test) ? And was the manager trying to advise you on what to do to, perhaps pass it?

Catalytic converters only work properly at high temperatures and if you don't warm the car up properly this may cause you to fail your E- test. Usually you need to drive around for about 20-30 mins or so, to get the car up to the proper temperature. Maybe he was trying to express that when he said what he did, as highlighted above?

If so, he was kinda right. You don't however, need to drive at 100kmph to ensure you're at the proper operating temperature. In a car that's in good working order, driving around conservatively for about 20-30 mins should ensure your exhaust system is at its optimal operating temperature AND ensure that the ECU is in its 'economical' mode so as to give your car the most probable chance to pass its E-test (smoke test).

Edited November 2, 2011 by Kavvz