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Old 04-09-2019, 01:49 PM   #501
Scooby Specialist
Member#: 375462
Join Date: Dec 2013
Chapter/Region: NWIC
Location: Portland, OR
2006 Impreza WRX STI
WR Blue


Originally Posted by jigga View Post
Thanks for the response

To answer your question, the answer is "both". I do have a standalone running the car most of the time, but my stock ECU does have to go back in occasionally for emissions purposes (and will have to go back into the car in a few weeks again actually), hence part of the desire to keep the stock FPC in the loop.

As is now, I can switch the stock ECU back in easily by just plugging it in and it is able to run the primary pumps on the car without issue, as it can power up the relay running the primary pumps, and run them at a constant speed.
I understand the issue - personally, I just register my car in a rural area at a family member's address. As long as you store the vehicle there now and then (and can reliably receive mail there), the DMV should allow it. I would NOT do this at an out-of-state address or a friend's address.

However - to continue with your current process, you can pull this off by sourcing a second FPC and making a jumper harness out of the 8 inch sub-harness it comes with.

A good trick to make sure you never mess this up is to make the standalone trigger the fuel pump relay using an opposite electrical signal when compared to the OEM ECU. For example:

If the stock ECU is sending a 5V 'enable' signal to the FPC (common to most 32-bit Subaru models), you set the relay up to close when the ECU sends a grounding signal.


If the stock ECU is sending a ground 'enable' signal to the FPC (which is how SOME 16-bit Subaru models work), you set the relay up to close when the ECU sends a 12V signal.

Side note - the 5V-active controllers WILL accept a 12V signal without any issue. I did it for years on a 2006 STI using a MoTeC M800 before converting to a relay.
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