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Discussion Starter · #1 ·
Apparently California has decided that modifying the ECU is now grounds for an automatic smog fail, even if the car actually passes the test. I floated the question past a friend who works for Jim Wolf Technology and this is what he had to say.
"After some information from a customer, it appears that this is how the smog testing station will check your ECU: "CVN stands for "Calibration Verification Number", this is a fancy name for checksum. What the ECM (or TCM) does is add up all the numbers within each segment of the flash memory, the total of those numbers is what the CVN equals. This allows people with a TechII to quickly check the data in each segment is correct or unaltered (eg, the CVN matches a known program). If any data is altered within the segment then the checksum (CVN) will change or not match what it originally was." Just to note, if an ECU software change is done and it is done to not alter the "checksum", then it will likely not be detected as a modified or changed ECU. That is my thought on this so far."

I bring this up as my 2002 WRX was flashed or something when it was new. I don't know who did it (Might have been ECU TEK) , but I do know that the ECU is locked and cannot be reversed or changed. I do not know if the flash altered the "checksum" or not.

How hard is it to swap an ECU out? Where is it located? I know from experience that some cars of that age do not allow you to swap the ECU without having a microchip that matches the key to allow the engine to start and stay running. (VW GTIs for example have this issue.) I don't know if Subaru did this sort of thing or not.

I would imagine swapping the ECU out isn't that big of an issue unless there is some antitheft deal like what VW was using at the time. Unplug the battery, locate the ECU, unplug the ecu, remove, replace, plug everything back in and reconnect the battery.

Does anyone have any thoughts on this?

Thanks,
Will
 

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Swapping the ECU is easy.

There is no anti theft.

It’s in the drinker side footwell near the center.
 

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Discussion Starter · #3 ·
My friend at Jim Wolf got back to me with some more info.

"I found out some more information. Our lab engineer checked and was able to find information that shows that the car manufacturers were required to report their ECU data starting in 2008. With that information it seems safe that 2007 and older models will not be affected by this ECU software smog check since the manufacturers never reported the data to the CARB from 2007 and back."

So, those of us with pre 2007 cars should be fine.

Will
 

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Dies this mean then that those with newer cars would have to buy a spare ECU and flash the spare? Am I understanding?
 

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That makes sense. Thanks for the post. It’ll help people in the future.
 
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