buy a new key, I swear I have posted this very same answer a couple of times...for no reason my key wouldn't work on my 1990 300, simply overnight for no reason. went and bought a new key and it's worked fine for 2 years plus. i still have the old key and look at it and compare to the new key...looks the same to me but the old key will not work and the new key does....swear to god that's the truth....