The Lexus had developed a slightly irritating ICE issue where the audio just stoped working. Sometimes it would go a couple of hours without it happening, other times it did it three times in 5 minutes. The symptoms were that regardless of input (I have tried bluetooth & Aux-in from my phone, and an actual CD (remember them?)), it would be playing music or podcast or whatever and then suddenly it would cut out and the nav screen displays 'audio off' - with Bluetooth or Aux-in it just stops, if its playing a CD then it ejectsed it.

Sometimes you could press the audio button and it would allow you to re-select the input and it started playing again, but often pressing the audio button did nothing, and it became basically non-responsive until you cycled the ignition. I discovered (during a long journey where I couldn't easily stop or pull over) that if left for long enough, it would magically come back to life if left alone for about 20 minutes and carry on though nothing had happened.

I've tried another phone in case it was my phone being weird, but happens with my daughter's phone too, and the CD behavior today is even more frustrating. I've not tried just listening to FM/AM radio to see if it does it with that too, but have no reason to believe it wouldn't.

Its both odd, and annoying. The car has the 'regular' audio rather than the Mark Levinson setup, I've hauled the amplifier out the boot a few weeks ago and opened it up and there was nothing obvious amiss in there, so plugged it all back in and the intermittent issue persists.

I'd really rather that it wasn't the head unit as a secondhand one (with no guarantee that this issue isn't present there too) is £300, and because its a smarty-pants Lexus, its not just the audio - the nav screen also handles the hilariously out of date maps, and rather more importantly the controls for the AC too. When the issue occurs though, its just the audio, the nav and AC controls work fine, so I thought that it was specifically an audio issue.

Filled with rage, and one rash purchase later...

The OEM stereo/nav unit in the IS250 looks like this:

Its sort of two distinct parts. When it does 'the thing' all the buttons in the lower section (red box) stop working, most notably the power/volume button in the top right. The top section remains working. This includes the nav screen, HVAC stuff, hazard lights and a few other things. The stereo also responds fine to steering wheel controls - I can change the volume and power it back on if off/off if on using the steering wheel buttons so I'm a little puzzled.

A complete nav head unit was somewhere between £150 and £350 on ebay which is a bit salty for me currently, however I had a brainwave (that's 2025's one used up....) earlier and found that it comes apart, so I might be able to buy just the bottom bit. A quick search later threw up a seller who had one which should be compatible for £35, with £12.50 of discount vouchers so I was able to bag it for £22.50 delivered. 

I aimed to try and remove and disassemble the current head unit, swap the new-to-me bottom part over, connect it all back together and re-fit it to the car and see if the problem persists. Its a bit more parts-cannon-y than I usually like but seems like a cheap option to determine if that was the issue. If it wasn't, then I know that its probably an issue with the top bit, in which case I can justify spending £250 on a new Teyes CC3 android setup and sack off the 2010 OEM Nav arrangement. I'm wasn't willing to do that until I was sure that its not something else though....

Anyway, I remained hopeful that it'd pitch up here in the week and I could have a play and see if I can break everything and trigger the immobiliser or some such lolz

Fast forward several days, and the bottom bit arrived well packaged and even including the reg number and VIN of the donor car, however I think* that I may be an idiot.

The lower bit of the stereo had arrived and I'm very happy with the service. It arrived well packaged, and with a slip giving the reg and VIN of the donor vehicle it came from. So far so good. I'd been hugely busy with work and general dadmin recently so its sat on a shelf in the study this week awaiting some time to get stuck in. Anyway, the other day I was driving to work and a thought occurred to me, the turning off antics only happened going over bumps, at a standstill, or on smooth roads it rarely ever happened. Maybe there was a loose connection? Then two of my remaining functioning neurons made a connection. Maybe the power/volume knob was partially stuck down?

Since this was easy to do, it seemed like a good place to start. I gently pulled it outwards and there was a pop and it clicked out. Since then, its not done the turning off thing at all! So I think that possibly I was a bit heavy handed and pushing the power button to turn it on, I may have jammed it partially in, and going over bumps may have caused it to power off with the connection being made.

I'll keep monitoring it, but I think I may have solved the issue - and as usual the cause was me being a ham-fisted dolt. Sorry Lexus, it seems like it was definitely user error!