Need help with ECU Nightmare
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Need help with ECU Nightmare
It looks like ive purchased a frankensiein Rx8 as it has a 2007 ecu program loaded onto a 2004 ecu and chassis/engine. Car ran terribly on this setup and blew its coolant seals shortly after, It was barley keeping its head above water idling. Its a 6 port 6 speed and the original ECU part number was scribbled over with the 2007 part number drawn onto it, but I can still see its original part number through the sharpie. Im trying to restoreall the ECU data to stock before I drop the motor back in rebuilt so I dont risk anything, any suggestions? It came with another spare ecu from another 06+ with who knows that on it. Can provide pictures if needed was using forscan to take a peek into it. Is there really any viable reason for someone to do this?
My suggestion would be to buy an 04 6 port ecu. I think you will also need to buy the key set with ignition cylinder and all of the locks. The down side is that the original car's vin will be written into the ecu still and a scan tool with think its the car that the ecu came from.
You may mot have to buy the key set and lock cylinder. If you were to buy a key from the dealer as if you've lost the key. The key should be able to be cut by the vin from your car. You should then be able to have the dealer program the new key to the car's new ecu as if that key were registered to the ecu originally.
You may mot have to buy the key set and lock cylinder. If you were to buy a key from the dealer as if you've lost the key. The key should be able to be cut by the vin from your car. You should then be able to have the dealer program the new key to the car's new ecu as if that key were registered to the ecu originally.
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The only f***up i see here is if the car was a 4 port engine and the ecu was for a 6 port, or the car was automatic and the ecu was for a manual(or the other way around).
In the case of 4 port 6 port swap, the fueling will be completely off, but idling and cooling etc. are identical for all model years...
In the case of 4 port 6 port swap, the fueling will be completely off, but idling and cooling etc. are identical for all model years...
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Im really not sure, but the asbuilt data does not match the original values for my car's vin. I know I can change the vin pretty easily with forscan from the old vin to my car's, and I believe the key chip too just a bit more dificult. Is there any ECU part number or protocol that I should specifically seek out over another or would any of the 6 port 6 speed ECUs from 04 work alright with a vin and asbuilt swap
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Of course it won't match. That is why it is called as built - because mazda made about 400 variations of RX8s by the time you sum up all the possible variations. What is important is that you match the powertrain types... manual/auto, 4 port/6port.
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I was mentioning it wont match since both I and the previous owner have ways of matching them, he for some reason chose not to match the asbuilt and only matched the vin and key fob. Im not exactly sure what features the asbuilt controls but I do have a stock sheet for it
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Restore stock ECU settings (2004) Use an ECU Programming Tool to reflash the ECU with the stock 2004 firmware (tools like ECUFlash or Tactrix are often used for Japanese cars, but you may need to check if it works for an RX-8)
Last edited by ROX206; Aug 29, 2025 at 07:35 PM.
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Ive got forscan to flash it back, but not too sure how to do so since everything on that ECU has been changed. I have not found an ECU for a reasonable price yet to buy for a port / 6 speed so im still looking for one to go that route.
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