ECU Swap out for OBD2????

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ECU Swap out for OBD2????

Post by Deane138 » Mon May 10, 2021 3:59 pm


So I have a 2005 Impreza 2.0 EJ201

Now in Australia, they made OBD2 communications mandatory from 2006 onwards

I'm wondering, If I obtain a 2006/7 ECU, could I just swap it out, and would that allow my off-the-shelf OBD2 plugs to communicate with the ECU???
I don't have an Immobilizer, so is there anything else an ECU swap would mess with?

I have tried multiple OBD2 plugs, even got a BluDriver with no luck communicating with the ECU.

Cheers for the technical advice/help

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Re: ECU Swap out for OBD2????

Post by El_Freddo » Mon May 10, 2021 10:23 pm

G’day Deane,

Good question! Your 2005 Impreza should already be OBDII compliant! I reckon you’ll find you’ll need to change the whole wiring loom to run the engine if you do go for an ECU swap.

Or study many wiring diagrams to see what wiring pins need to change at the ECU. You might need to change ECU plugs to accommodate the new ECU.

It could be more cost effective to drop an aftermarket ECU in there, tune it and watch the parameters from there if that’s what you’re trying to achieve.

It’s lots of work though. A scan gauge could work well. A couple of mates used them from a modified ‘98 Liberty to a 2007 XT forester.

I’m sure there’s a simpler way to get to your goal than what I’ve come up with...


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Re: ECU Swap out for OBD2????

Post by Deane138 » Tue May 11, 2021 1:01 am

So I have an OBD2 port under my steering wheel however it doesn't communicate with any plugs,
I can't find the previous website however, this one also states that they became mandatory after Jan 1st 2006 ... -s/153.htm

I've also seen a bunch of videos online of people swapping ECUs out on Imprezas, aslong as the ECU model number and Transmissions are the same.

So I figure it has to be the ECU that's not communicating with my obd2 plugs, as they light up, just no connection.

and I can get a second hand ECU for sub $100, but an aftermarket ECU + Tune would be much much more.
I just want to be able to read my vehicle data like Fuel air, engine codes and all the information so I can better diagnose any issues, instead of chasing a bunch of possibilities like I have in the past.

So has anyone had any luck swapping ECUs?
Does anyone have an Impreza pre 2007 that works with OBD2?


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Re: ECU Swap out for OBD2????

Post by TOONGA » Sat May 29, 2021 10:32 am

Deane138 you need a code reader that will work with your OBD2 plug, do you have one?

You will find that some years of the Impreza will only work with a certain type of scanner.

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Re: OBD2 ...

Post by Bantum » Sat May 29, 2021 5:55 pm

I looked into using OBD2 & from my understanding Subaru in there wisdom decided to rewrite the software code, making it impossible to read from a normal scanner, you'll need to get a scanner that talks to the ECU with the correct format + they is really hard to find ... :/

So yes, only real solution is to upgrade the ECU ( and associated issues that brings ) if you want to plug & play with OBD2 compatible parts ... :roll:

Cheers, Bantum ...

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