Auto-learning....two Stages.

[wwest]

Okay, here is my FINAL answer.

The absolutely correct one.

Modern day cars are shipped from the factory with only rudimentary "tutoring".

All of the engine fuel mixture and performance parameters are loaded into their respective ECU (ROM?) memory tables as preliminary approximations.

For instance, my 1993 Ford Ranger with an I4 has an idle air bypass solenoid that is used to provide a linear function. As time goes by the engine ECU "learns" how to correctly pulse width modulate the idle bypass solenoid so that the oxygen sensor in the exhaust path indicates no unburned oxygen.

If you disconnect and reconnect the battery to go back to the factory approximation settings the I4 does not pass the WA idle emissions test. Drive it around for two days and the engine ECU "learns", deterministically, what pulse width modulation values to apply to the idle bypass solenoid under the engine various operating parameters, engine temperature, inlet air temperature, and absolute pressure.

I would guess that many more modern cars operate in the same way, all the tables and parameters for approximately correct operation are loaded at the factory and those parameters are then continuously updated, for fuel economy, low emissions, and driveability, as you drive. Obviously the battery disconnect/reconnect procedure would cause the system to reload the factory default approximations and then the learning process would begin all over again.

So, no question, "reset" the car's ECU's via disconnecting and reconnecting the battery and the drive "feel" of the vehicle will suddenly be different, at least for a few days ormiles.

But what about learning individual driver's driving styles??

Within0 seconds of having started the car and put it into motion the engine and/or transmissions ECU(s) will have preliminarily "mapped" your personal driving style. After three minutes the ECU's will have come to a "final" conclusion on where to place you within the various driving style parameters. As many as 10 driving style "modes" seem to be indicated by one of the European marques.

Thereafter the ECU's keep a "running" three minute history and if you suddenly become more aggressive or passive it will then remap you into another "style".

So the dealer mechanics and technicians statements are correct, resetting the ECUs WILL change the vehicles driving charactoristics, "feel". But with a fairly short period the ECUs will have learned the best parameters for the vehicle's operation.

[mh6]

Yes ....finally its final :P

Just kidding dude ...nice write up :)

[ColinBarber]

Resetting the engine ECU will clear the long time fuel trim. Also the timing will be set quite low and will then try to advance, using the knock sensors to not advance too far.

Once the correct point for timing is found the ECU doesn't try and advance too often, which is why it can take a tank or 2 of fuel before any benefit is found when going to a higher grade fuel - if you reset the ECU it will accelerate the learning again.

Gearbox learning is again something different and Toyota don't seem to release too much information on how this is achieved.