So I was about 300 miles from home taking my son to a graduation weekend fishing and we (attempt) to stop for dinner. Upon trying to park and turn off the car, by pressing the start/stop button, the engine will not turn off. The ACC display stays on 100% of the time and the nav screen cycles through power on/off. I searched the forums here and other places and found only a few potentially helpful links. I replaced the fob battery and confirmed the car is in park. I finally made it to my destination by refueling with engine running. And for those curious, to actually get the engine off, I pull a fuse from the box, then disconnect the battery. When I eventually plug the battery back in (fuse in first) the car returns to its normal wonky state (acc on, won’t turn off but I can start the engine). I’m hoping and praying this fine group may have a user-serviceable idea or solution for this. Like it’s a coding thing where somehow I need to recode the key (made that up) vs a hardware issue like the alternator.

Any suggestions on what it could be? Dealer has had it 2 days and can’t get to the bottom of it. Thank you all!

 

I am having similar problems with a 2006 gs430.
It is a long running problem that, with covid and work issues, I have just ignored until now.
The car had been running faultlessly for years but then developed the habit of running the battery flat when left for any time (overnight).
I noticed that on shutdown, although the engine did stop, the steering column didn't park and systems stayed on. I suspect this was draining the battery.

So I am now 2 years down the road with a brand new battery, tyres, MOT (roadworthiness check) etc, paid the bill and collected the keys, hoping to get the car back on the road.
The car had been delivered home last week (I work away) but when I tried to start it, the battery was flat.
I jump started it and took it for a short drive, all seemed ok until I switched it off. Then I found, as before, the same symptoms, not parking the steering wheel and loads of system lights staying on.
I have a tech stream set up that I will use to see what I can find and will report back.
Please let me know if you find a solution.
If anyone else has seen this behaviour and has a fix, please let us know.

 

You might have a parasitic draw.

 

Check your relays. Especially the one that turns on the accessory system like your steering wheel adjustment. If the relay is sticking, it could be keeping the system powered on.

 

Update:
battery has been isolated from vehicle and fully charged overnight.
Reconnected this morning and things looked good initially.
TIS could not find any faults.
Started up and then had an incomplete shutdown.
Playing with steering tilt and reach, and shutting down with foot off brake has produced a complete shutdown.
I will start driving it, taking a small booster pack that i bought from harbour freight just in case.
I will also brief SWMBO (the Mrs) so she can check to be sure of complete shutdowns as well.

Will update further.

Now I can start fixing my rx450h check hybrid system.

 

We are one week down the road now and I have seen a few partial shutdowns that were solved by using a longer press of the start stop button. Hopefully that is it resolved.