ECU Reset on WRX: A couple of Questions....

[CompUser]

Greetings...

New poster on Alt.autos.subaru here..just picked
up an 04 WRX mt..

1. What fuse supplies the computer? Surely we
can do a reset without pulling the battery
cable...

2. By doing a power-off re-set, do we lose any
valuable info (I'm only a week into purchase
here, on a demo model), like some knucklehead
over speeding the engine prior to my purchase?

Thanks bro's,
Steve

 

[imaginuity]

ask your dealer spare parts/service manager or go-fast shop that has
expertise in your model vehicle - I am uncertain but imagine car ECU's have
a back up battery in them to enable battery-off servicing issues to be
address.

Finally, why would you wish to reset it anyway?

 

[CompUser]

(e-mail address removed) says...

ask your dealer spare parts/service manager or go-fast shop that has
expertise in your model vehicle - I am uncertain but imagine car ECU's have
a back up battery in them to enable battery-off servicing issues to be
address.

Finally, why would you wish to reset it anyway?

According to some info I've read online, the WRX
ECU will detect a variety of changes in operating
conditions (such as lower octane fuel) and make
changes to engine ops correspondingly...but that
it won't "re-adjust" the performance specs back
upward, when higher octane fuel use is
restored...that an actual reset was required to
get the ECU to consider it's options in that
area, once again.

I'm putting only 92/93 stuff in, but who knows
what might have made it's way in their prior to
purchase ;-)

Steve

 

[CW]

Lower octane ultimately translates into knock. The knock sensor will
"hear" this and the ECU will retard timing accordingly. It takes a
while after favorable conditions are restored for the high performance
settings to return. The ECU has no fuel analysis per se.

CW

 

[Jeff Lackey]

According to my mechanic at the Subaru dealership, the only way to reset the
computer on a WRX is to use the factory diagnostics computer that plugs in
underneath the steering wheel. I believe all the other methods are just
"shade tree" and don't really work. From my experience this seems to be
true, as I felt no discernable difference after attempting a reset by
disconnecting the battery and hitting the brakes. It took my mechanic about
15 seconds to reset the computer (which he did for free, because he a really
nice). The difference was quite noticeable. Jeff

 

[CompUser]

@newsread1.news.atl.earthlink.net>,
(e-mail address removed) says...

According to my mechanic at the Subaru dealership, the only way to reset the
computer on a WRX is to use the factory diagnostics computer that plugs in
underneath the steering wheel. I believe all the other methods are just
"shade tree" and don't really work. From my experience this seems to be
true, as I felt no discernable difference after attempting a reset by
disconnecting the battery and hitting the brakes. It took my mechanic about
15 seconds to reset the computer (which he did for free, because he a really
nice). The difference was quite noticeable. Jeff

Thanks Jeff! ...if I may nit-pick for a bit, how
long do you think you had the battery
disconnected?

Steve

 

[Ken Gilbert]

According to my mechanic at the Subaru dealership, the only way to reset the
computer on a WRX is to use the factory diagnostics computer that plugs in
underneath the steering wheel. I believe all the other methods are just
"shade tree" and don't really work. From my experience this seems to be

this is not true... resetting the power DOES reset the ecu settings,
and has been verified with delta dash, a computer-ecu interface.

the absolute easiest way is to turn on the dome lights, go under the
hood, remove a battery terminal, and simply wait for a minute. you
know you've removed power long enough when the radio has lost its
presets and your trip meters have been zeroed.

you will also find some pertinant information on nasioc.com. look in
particular for the "shiv ecu reset" method, which increases the
baseline ignition advance multiplier from 8 (default after reset) to
16. if you've got the octane to sustain it this is worth HP.

jm2c
ken

 

[CompUser]

@posting.google.com>, (e-mail address removed)
says...

this is not true... resetting the power DOES reset the ecu settings,
and has been verified with delta dash, a computer-ecu interface.

you will also find some pertinant information on nasioc.com. look in
particular for the "shiv ecu reset" method, which increases the
baseline ignition advance multiplier from 8 (default after reset) to
16. if you've got the octane to sustain it this is worth HP.

Hey Ken,
Believe it or not I just ran across his posting
on nasioc, minutes before reading your post.

I'll take Shiv's word on it, seeing as he makes a
living working on these ECUs, etc ;-)

Time to make a run to WalMart and pick up a few
50# sacks of dogfood...while the neg cable's off!

Steve