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Old 07-15-2021, 09:42 AM   #5 (permalink)
JSH
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CARB knows exactly how OBDII tuning works. Depending on how they implement their check will determine if simply flashing back will work. They could look for modified file names, the checksum, the tamper bit or all of the above.

Flashing an ECM changes the checksum. Most manufacturers (maybe all by now) put a "tamper bit" in their ECM. If the checksum ever doesn't match the correct value it flips the tamper bit which is memory that is not rewritable. That flags the ECM as tampered permanently even if it is flashed back to the factory tune. Manufacturers do this to combat warranty fraud were someone tunes a car, damages it, and the puts it back to stock and tries to file a warranty claim.

If CARB is just checking for files names and the checksum then flashing back will work. If they are checking the tamper bit then tuned cars will need to have a stock ECM to swap back in for smog testing. From my reading on this Massachusetts already checks for tunes and checks the tamper bit.

Checking the ECM is also a way to check for internal modifications that aren't visible If you have done hidden modifications (cams, pistons, valve work, gutted cats or DPFs, etc) it may be hard to get the car to run right on a stock tune.


At the end of the day this is about making illegal modifications more expensive and a hassle. This should help move people to legitimate tuning companies that do legal tuning and performance upgrades.
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