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I just moved this from a previous site, didn't think I was in the right area. My 97 ls 400 with 150k is a terrific car. It has been well maintained with all services performed on it. Because the car wasn't starting, we were taking the simple route first to rule out the transponder keys. The keys checked out ok and the car still won't start. My mechanic believes the problem is in the immobilizer system and is changing the "amplifier" which I believe sends a signal from a transponder key to the rf remote security center that tells the car to start. I've been told that they don't believe it is in the ecm, as there are no codes and the car was running absolutely beautiful until it decided to just spin over without starting. It turns over but doesn't want to start. Has anyone experienced such a problem, and if so how was it resolved? Does anyone have any suggestions?

I am desparate for help. thank you.