2003 RSX Base with 2006 K20A3 Engine – ECU Compatibility Question

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GalaxyRSX
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Joined: Tue Sep 16, 2025 1:54 pm

2003 RSX Base with 2006 K20A3 Engine – ECU Compatibility Question

Post by GalaxyRSX »

I have a 2003 Acura RSX Base (automatic) with the following setup:

Body VIN: JH4DC54853S003585 (2003)
Engine VIN: JH4DC54856S019824 (2006 K20A3)
Installed ECU: 2003 ECU, part #: 37820-PND-A57

I’m trying to figure out if my current ECU (A57) is fully compatible with my 2006 K20A3 engine, or if I would need the stock 2006 ECU (A66) to avoid EVAP codes and ensure proper tuning.

I currently have this 1457 EVAP code I usually can work around for inspection, but as of recent it doesn't listen to the required parameters to turn the CEL on (Keeping the gas tank above 85% full). I've replaced the whole system 4 years ago with not even professionals finding a leak.

Would this cause any compatibility issues? I believe they are both K20A3 engines for those years. I bought the car this way, not sure what the previous owner's intentions were.

Any advice or experience would be greatly appreciated!

Thanks in advance.
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