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

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...

  1. 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

Reply to
CompUser
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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?

Reply to
imaginuity

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

Reply to
CompUser

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

Reply to
CW

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

Reply to
Jeff Lackey

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

Steve

Reply to
CompUser

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

  1. if you've got the octane to sustain it this is worth HP.

jm2c ken

Reply to
Ken Gilbert

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

Reply to
CompUser

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