Gx 470 Will Not Start And Shuts Down While Driving

[lkojr]

I have a 2003 GX 470 with 49,000 miles. Car has been running fine until about 4 weeks ago when I took it in for some warranty work (replace seat belt after airbag warning light was coming on). Got the car back drove fine for a while, but then it wouldn't start. Turned the key and the thing was dead, no clicking nosie or anything. The battery checked out fine so it is not a battery or alternator issue. There were also no codes in the system that anything was malfunctioning. While the tech was test driving it during service, he said the car just shut down on him as he was driving and he had to pull off the road. It took Lexus 2 weeks to diagnose the supposed problem - they finally said it was the Engine Control Unit that was bad so they replaced it under warranty.

Drove out town and has been working fine for a day or two. However, the problems started happening again. Got in the car and turned the key about 15 times and nothing happened. I tried starting it in park and neutral and neither worked. All of a sudden it worked again and was able to drive it to a safe location a short distance away. Now I am afraid to drive it anywhere in fear that it will shut down on me and cause me to get in a major accident.

Can anyone help with this one? Anyone had a similar problem?