Ecu

[is200 Newbie]

Can anyone shed some light on this - I think it will be useful for people to know also ...

Its handy knowing that it needs to be reset for various reasons and it does seem to reset the driving style of the car but what does it actually reset, what does resetting it actually do?

Which Battery lead do you need to disconnect, Negative or positive or does it matter?

How long does it take to reset?

How long does it take to re-set to the driving style?

What settings do you lose? (windows / seat memory / radio stations / some sat nav settings)

Do you need to drive it in any particular style, as normal or heavy/light foot?

Are there any likely fuses that blow when connecting the Battery back up?

[Pac Man]

Hi Noo bie

The first part to always get right is the Battery connection/ disconnecting phase,

Always always disconnect the negative(earth)lead first and then the positive and when reconnecting ensure the negative goes on last so earth of first earth on last.

This will ensure the best possible protection for the delicate circuitry inside the ecu's.

Also if any members ever have to have the unfortunate issue of a car needing any welding ,then once the Battery has been disconnected (as above) then the positive and negative leads need to be bolted together and the welder should always connect his equipment as close to the repair area as possible.

Connecting the leads together effectively makes the complete car wiring system many miles long and will help the dispers the large electrical current generated thus again protecting the very expensive ecu's

[is200 Newbie]

Good point - I wasn't aware of the need to disconnect the earth lead first ...

[Pac Man]

Ecu's send and receive data mainly via what's known as a canbus line this is different to normal vehicle wiring, it is identified by two wires twisted together (100 twists per meter) one of the twists is refered to as can high the other is can low - the twists are to prevent interference from other electrical sources which can effect the data communication between the vehicles various ecu's

All ecu's are programmed with a priority number in accordance with there respective importance - say a braking ecumenical will be a 1 where as climate control will be high a higher number. They are given numbers to enable the driver to be able to control what he wants when he wants ie if you are driving and a passenger changes the temperature in the car and the driver presses the brake then the temperature request will be shunted down the data (canbus) line. Of course you will never know due to the incredible speed of all the data flowing around the car, I won't go into the the transfere rates in case I'm over complicating things !- which I might already have !

So what does all of the above flanel mean - by disconnecting the ecu you are resetting the data logs much the same as if you switch off your phone and remove and replace the Battery or run a defrag on your home computer

All the ecu's will communicate easier and quicker thus being more responsive to the inputs from the driver

Hope this sort of helps? And explains a little the basics of ecu communications

paul

[is200 Newbie]

Thanks Paul

I get the principle now - more by the comparison of defragging your pc.

I just always wondered what was happening during the reset process when I saw comments from users advising to "reset the ecu". So in a way it makes sense to reset it maybe once a year when servicing to clear the logs.

[Pac Man]

it won't do the ecu any harm - the only risk of course is from an electrical spike ! So best keep the disconnects to a minimum

Forgot to mention - use the Battery disconnection method if you ever connect a jump start pack or from another vehicle you tend to get more damage from these scenarios than anything else !

[Pac Man]

So for Battery jump pack connections its Earth cable on first - disconnect LAST to the flat Battery