I have an 07 lexus GS350 and I recently started experiencing an issue with my car randomly not starting. I would push on the brake and the start button but the car would only power on the radio /ac. The car would not attempt to crank. I originally suspected it was my key fob because one of the clips that hold the battery in place broke. I would take the key apart and push the battery down on to.the connector and after a few tries the car would crank. I switched out the fob for a brand new never used fob I had for years that I just recently programmed and after 3 weeks of use I experienced the same issue. I took the battery out of the new fob and put the battery back in and the car cranked. This issue has never happened off a cold start only after I drive the car and made a few spots requiring me to crank the car. I have tried troubleshooting this issue with no luck. I tested the car battery test its putting out 12 volts and around 14 when running the a/c. The battery and alternator seem good. I had the starter test at the local Auto Parts store and it was good.also. I connect a scan tool with live data and everything seem to be within spec. I just changed the battery in the new key fob to see if that battery was going dead. Has anyone else expereinced this issue or can lead me in the right direction on what else to check. I appericate everybody's help.as always.

 

Not speaking from experience (never had such issue with my 3GS) but from general practice in dealing with no-start situation, first thing to check is there is a positive starting signal sent to the starter, or to be precise, the starter solenoid, a cylindrical shape device that is bolted to the side of the starter motor. This solenoid does two things when it is powered up, 1. sliding the gear on the starter motor shaft out to get it to mesh with the engine flywheel so that when the motor turns it cranks the engine, and 2. closing the starter motor connection to the battery. The solenoid makes a clicking sound that is easy to identify when it is doing those two things.

When you are re-trying to start the engine that has just failed to start, go from the radio on A/C on state, pay close attention to a clicking sound coming from under the engine. and go from there.

I think you can leave the remote fob alone for now. It's quite unlikely that its battery/connection is okay when the car is cold, but gets weak when the car has warmed up, especially when you don't have low fob battery warning on the dash.