Problems when doing a long trip

[Stephen123]

Good day, I bought a GS450h 18 months ago and just love driving it, lovely car. I live in Whitianga which is a small town in New Zealand and to go anywhere of some distance one needs to cover 1 hour of hilly and winding road. While I drive the car around town here, there is no problem at all, everything is great. However, since owning the car ( its a Japanese import ) when I drive over the hills, eventually the red triangle light comes on, and sometimes the yellow engine block light comes on.

Also on a few occasions I have found that after completing a trip of 2-3 hours, when I try to restart the car it wont start unless I keep pushing the start button when the engine will kick in, if I try to put it in gear straight away it will stop but if I wait 30 seconds or so I can get it into gear and drive it but the hybrid electrics will not kick in, engine will stay running, and red triangle and engine block lights stay on. After using the car a couple of times, the warning lights still on but everything else running fine, the lights will then disappear and all will be fine until the next long trip I do. Its weird and a bit inconsistent. I have taken it to Lexus 4 times, and they originally diagnosed the problem as transmission pump and controller error so I had both of these replaced with new parts. This still didnt fix the problem and they have tried various other tests over time, including replacing the battery in the boot, 12 volt, still no better. It seems the problem may be related to heat driving the car over a longer distance however Lexus are still baffled as to the real issue. If anyone has experienced something similar, or has any ideas, please let me know, I would be very grateful. Cheers, Steve