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I'm in Cleveland, OH, and my 2005 Elise "Forgot" its VIN. I talked to Lotus USA about this, and I've read every thread here about the subject. Having been an embedded systems software engineer for 20 years, I'm not clear on what the problem is, except, apparently, if you run the battery dead enough, the ECU "forgets" its VIN. Oddly, Lotus USA said it could also be "You ran the battery dead too many times". Since the car doesn't "forget" its VIN every time you change batteries, I'm assuming there is some capacitor or "battery" on board the ECU that is responsible for remembering the VIN over short periods of power interruption. Clearly the VIN is not permanently programmed in non-volatile memory.

Cleveland apparently doesn't have a Lotus "dealer" anymore, but the former Lotus dealer has advised that they can still service the cars, including reprogramming the VIN for $205 "if all goes well". My prior experience with this dealer is that nothing ever "goes well" and the bill is always double the estimate.

I'm looking for recommendations on rectifying this silly CEL, in anticipation of selling the car. If anyone has recommendations, I'm all ears - including removing the ECU and sending it somewhere.

Thank you in advance for any advice!
 

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the vin is stored in non volatile memory and loaded to and from ram at power cycles. this allows the user to change the vin in ram and have it retained in the car, rather than having a vehicle specific copy of the firmware.

since flash rom is erased in blocks, if the copy from ram to flash memory is interrupted at the wrong time (after erasing, but before the write), then i expect the vin to be lost.

you can reprogram the vin with an obd command, mode 3b, pids 1 and 2.

https://www.lotustalk.com/forums/f171/how-partially-diy-set-vin-ecu-your-2005-lotus-elise-381737/
 
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