My LX570, 2012 model has stopped responding to the remote.

5-2. Steps to take in an emergency 5 Changing “ENGINE START STOP” switch modes and starting the engine Shift the shift lever to “P” and apply the brakes. Touch the Lexus emblem side of the electronic key (including the card key) to the “ENGINE START STOP” switch. An alarm will sound to indicate that the start function cannot detect the electronic key that is touched to the “ENGINE START STOP” switch if any of the doors is opened and closed while the key is touched to the switch. To change “ENGINE START STOP” switch modes: Within 5 sec- onds of the buzzer sounding, release the brake pedal and press the “ENGINE START STOP” switch. Modes can be changed each time the switch is pressed. (P. 173) To start the engine: Press the “ENGINE START STOP” switch within 5 seconds after the buzzer sounds, keeping the brake pedal depressed. In the event that the “ENGINE START STOP” switch still cannot be oper- ated, contact your Lexus dealer. STEP 1 STEP 2 STEP 3 LX570_U (OM60F86U) 683 When trouble arises

For example this is on page 583 ... See manual for more details.