Quote:
Originally Posted by alex77ae
How does the key loose its ews value? it still sends data.
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Honestly, I'm not absolutely sure how EWS components get out of sync...other than something major or unusual probably occurs...like a power surge, or if one of the components is disconnected/swapped/replaced with another component that's not coded to the car (by owners unfamiliar with the idiosyncrasies of EWS).
One example, a forum member on a 7 series forum from Europe had purchased a blank key on eBay and had the blade cut to fit his ignition. He wanted to know why his original key no longer worked. After getting more details...he had first inserted his original key, then shut down the engine and removed the original key, then promptly inserted the eBay key which started the vehicle. He then proceeded to drive the car, but when he tried to start his car the next time (using the original key) it no longer started the car, then he tried his new eBay key, and it wouldn't start the car either. He didn't know why. Well, there's a 10 second window right after engine shut down where EWS doesn't ask for the ISN if the car is restarted...so when he inserted the eBay key, within this short window, the car started. But this caused the rolling codes to go out of sync since he used a key that wasn't coded with his car's ISN
If your car falls under EWS 3.3...it contains "rolling code technology" which changes a series of numerical tables with each use...so, if an electrical surge interrupts a component or a foreign module is inserted into the mix and a failed attempt to start the car occurs...the components can become "unsynced". But for the most part...this is a rare occurance.