So the past month while I’m stopped at a light with my foot on the break the engine will come on even though the battery is fully charged. Then shut off and it will go back and forth a few times then I’ll drive and it will stop.

I’ve also noticed that when I’m at a stop I feel like I need to press harder as the rear breaks don’t feel like they are holding as strongly even though they were fixed -new rotors and pads- a few months ago. Any idea if they could be related or separate issues?

 

I have noticed that ICE turn on and off specially after the first warm up from cold. [I drive to warm up the engine]. Other than the observation there are no adverse conditions, so I attribute this to programming done by Lexus/Toyota engineers.

How long have you been driving 450H? Braking is pretty unique in hybrid. Slowing down is mostly accomplished by the front and the rears essentially keep the tail behind the slowing down front. In hybrid the kinetic energy being absorbed is recovered to charge traction. This results in less brake pad use and the rears brakes get used a lot less and that can cause brake system to bind [use it or loose it]. The other oddity is that when you are stopped and ICE kicks in, you have to hold the brake pedal a bit harder [analogy is stopping at an incline or non-hybrid].

If you have a feeling things are not normal or as expected then take the vehicle back to who ever fixed it.

The key is establishing what is "normal" and most of the things are by feel. That is why I asked about the duration of ownership.

Salim

 

I’ve owned my RX for going on 10 years and I’ve never noticed it doing this until after I had a break job done a few months back at an independent shop

 

Brake job should not be the cause of this observation.

I can only suggest visit the dealership and see if they find something. A well equipped non dealer specializing in Lexus/Toyota hybrid may have the equipment to read off the computer(s) inside your RX.

Salim