Reset the ECU?

[H]

According to my 04 Forester service manual the 24000km service includes
resetting the ECU. When I asked the my Subaru Service Manager if this was
done he said they generally do not reset the ECU unless there are problems,
this is a learning computer and will correct itself as time goes on. Why
does Subaru have this as a service item at 24000km and my service guy is not
doing it. Time to write Subaru Canada I think.

 

[mulder]

According to my 04 Forester service manual the 24000km service includes
resetting the ECU. When I asked the my Subaru Service Manager if this was
done he said they generally do not reset the ECU unless there are problems,
this is a learning computer and will correct itself as time goes on. Why
does Subaru have this as a service item at 24000km and my service guy is not
doing it. Time to write Subaru Canada I think.

I recall seeing this posted before, apparently it is considered a
service item in Canada? Normally there should be no reason to do a
reset and it really doesn't matter since the ECU is constantly
learning and adjusting fuel and timing based on 02 and knock sensor
inputs. If it is reset it will begin the learning process all over
again, but ultimately end up in the same place.

 

[Ross]

According to my 04 Forester service manual the 24000km service includes

I recall seeing this posted before, apparently it is considered a
service item in Canada? Normally there should be no reason to do a
reset and it really doesn't matter since the ECU is constantly
learning and adjusting fuel and timing based on 02 and knock sensor
inputs. If it is reset it will begin the learning process all over
again, but ultimately end up in the same place.

The ECU is reset as it never forgets so if you run low octane or poor
quality fuel and the timing is retarded this will always be factored in on
the equation. If you run on 95RON timing is retarded but it will never be
fully advanced when you go back to higher as the rolling calculations always
use the data from running on 'bad' fuel. The reset is performed to allow
the engine to reconfigure itself without the history.

I had my sti done as I got caught out and was forced to put regular in it,
took it into the dealer and had it reset once i had 98 in it, performace
returned to normal!! And the dealer confirmed the above...

R

 

[mulder]

The ECU is reset as it never forgets so if you run low octane or poor
quality fuel and the timing is retarded this will always be factored in on
the equation. If you run on 95RON timing is retarded but it will never be
fully advanced when you go back to higher as the rolling calculations always
use the data from running on 'bad' fuel. The reset is performed to allow
the engine to reconfigure itself without the history.

I had my sti done as I got caught out and was forced to put regular in it,
took it into the dealer and had it reset once i had 98 in it, performace
returned to normal!! And the dealer confirmed the above...

R

AFAIK the ECU should eventually get back to where it belongs, however
it can take a relatively long time to return to normal after a tank of
bad gas and severe knock events. In such a case, if you know that low
octane fuel has been run through it, it would be advantageous to do a
reset. Otherwise, in normal use and with the proper fuel having been
used, there is little or no benefit to be realized from a reset.

 

[Edward Hayes]

If it's a Subaru recommendation just do it. I reset mine about once
every 15,000 miles. This reset the default engine parameters to the
"new" car settings. When I do this my mileage drops about 1 mpg for a
tank or two and slowly returns to my driving style, be it aggressive
or mild. I do my reset by myself by disconnecting the negative battery
terminal for about 30 minutes while I press the brake pedal several
times. You will need to reset your radio stations so record them
before hand. Ed

 

[Ross]

AFAIK the ECU should eventually get back to where it belongs, however
it can take a relatively long time to return to normal after a tank of
bad gas and severe knock events. In such a case, if you know that low
octane fuel has been run through it, it would be advantageous to do a
reset. Otherwise, in normal use and with the proper fuel having been
used, there is little or no benefit to be realized from a reset.

I will never get back to the optimum but will get close. Imagine the
following

10,10,10,10,10 = Average of 10
10,8,10,10,10 = Average of less than 10. Until you remove the 8 from the
running average your average will never be 10 regardless of how many more
10's you add!!

Remeber as your engine wears the ecu is still processing data from the nice
new tight engine 24000 miles ago which may not yeild the best results, the
reset eliminates the old data that may be irrelevant.

Rossco

 

[John O]

I will never get back to the optimum but will get close.

True, but close might be good enough if you account for rounding, or if a
rolling average is used.

-John O

 

[Mike]

But i thought that the ECU only saved data from the last 500 miles. If so,
a bad tank of gas longer ago than that wouldn't matter.

 

[H]

But. 10,9,11,10,10=10 so you can, in theory, get back to 10

10,10,10,10,10 = Average of 10
10,8,10,10,10 = Average of less than 10. Until you remove the 8 from the
running average your average will never be 10 regardless of how many more
10's you add!!

 

[Ross]

But. 10,9,11,10,10=10 so you can, in theory, get back to 10

Not if 10 is the maximum

 

[John O]

But. 10,9,11,10,10=10 so you can, in theory, get back to 10

10,10,10,10,10 = Average of 10
10,8,10,10,10 = Average of less than 10. Until you remove the 8 from the
running average your average will never be 10 regardless of how many more
10's you add!!

You don't keep adding 10's in a running average! The early ones fall off. In
your example, two more 10's and the 8 is gone.

-John O

 

[H]

I didn't see any rules stipulating 10 as the maximum.

 

[MisterG]

I give this thread a 10!

I didn't see any rules stipulating 10 as the maximum.

 

[Edward Hayes]

If 10 is the maximum and one number is 9.999 you never get back to 10
as the number trying to reach 10 become asymptotic out to infinity.
The realistic question is how many groups or numbers does the
computer use for the averaging.