Hope everyone had a wonderful and Happy Independence Day.

Since we had 4 days long weekend and with some other tie-ups, we stayed local mostly in the bay area. I was able to wrap up changing fluids all around my GS, put in new air and cabin filters as well as Michelin MXM4 tires all around.

Does anyone know of a fuse or a bulb that provides backlit around radio area at night? I checked friend's 2019 GS and it has nice backlit at nights and all radio buttons show up with backlit. Someone the radio I got shows no backlit once it gets dark. I had Acura TL that had similar problem and it was due to a blown fuse and my older Toyota in late 90's had a bulb blown out causing same problem.

Not sure what the root cause is. I opened radio from dash and found all connections secure in back. Radio works normal with all buttons except that backlit issue.

Hoping someone would have run into this and fixed the problem.

 

I am referring to the red circled area. I might have added confusion by saying it happens at night because my headlights are set to AUTO.|

When headlights are off the area above shows everything lit including two temperature read outs for driver and passenger sides. The moment I turn headlights on, all of that area goes dark as if some bulb/LED behind that area turns off the moment I enable headlights (also noticed that the volume button on that console doesn't work at the same time). Once I turn off headlights (or set to AUTO during daytime which turns headlights off), console area around radios lights up and power volume button works fine.

I checked all the fuses in all the areas in car based on details shown in fusebox-info site for our car model. Didn't find any fuses to be blown. I don't know if any relays would cause this. I removed radio once again and didn't find any cables loose. Radio works perfectly fine except for that lighting issue.

Hopefully someone can provide some help

 

I don't have the knowledge to help here, but was wondering if your dimmer is set to full low? That's the first thing I'd check.

 

I already tried adjusting dimmer from low to all the way full near steering side. I am not sure if there is any other dimmer for console area or if there is a setting in one of the menus.

 

@bayareaemt - I think you'll find that it is operating correctly based on ambient lighting, headlight operation, etc. Same goes for the soft lighting in the doors above the armrests, front and rear footwell lights, inside door handle lights, ornament lights, etc.

► FYI - When the instrument panel light control switch is turned to 'minimum' level and the tail lights
are On (like when driving at night) the inside door handle lights, the ornament lights and the footwell lights will
turn Off. This is to prevent being distracted from interior lighting while diving at night.


You should try your HVAC in AUTO mode (center button) and let the high-tech Lexus HVAC system control the condition in the cabin by choosing when to alternate bringing in outside air versus to recirculate cabin air. I think it does a fantastic job of making the cabin very comfortable.

 

He said there is no backlight on the buttons at all when the headlights are on, so assuming he is testing this feature at night and is also describing the issue correctly, it sounds like there is a problem.

I second the suggestion of using auto mode for your HVAC, mine is on auto 99% of the time, keeps the car very comfortable.

 

I don't remember if I asked before, but do the pre-facelift's heated/cooled seat buttons light up? They'd be just under your picture. At least on mine, the radio/HVAC buttons and those cooling seat buttons both light up with the same intensity when the headlights are on.

Regarding the volume not working when headlights are on: Does any other function of the radio stop working when you turn on the headlights? I'm guessing the sound doesn't cut out but does skip/tune work? Does volume control from your steering wheel work while your headlights are on?

The only ones that stick out from the fuse site are the following, though you'd likely notice other systems not working:
From driver side interior fuse box:
#22 A/C 7,5 Air conditioning system

From the passenger side interior fuse box:
#8 RH ECU-IG 10A Navigation system, VGRS, pre-collision seat belts, air conditioning system, Lexus night view
#14 MULTIMEDIA 10A Navigation system, Remote Touch
#18 ACC 7,5A Body ECU, head-up display, RR CTRL, navigation system, transmission, Remote Touch, DCM, Remote Touch screen

Engine compartment, passenger side:
#9 DOME 7,5A Personal lights, ornament lights, trunk light, footwell lights, door courtesy lights, vanity lights, rear door inside handle illuminations, power trunk opener and closer

Engine compartment, driver side:
#17 TV 7,5A Remote Touch screen

​​​​​

 

The only time I take over is when it chooses feet mode on the way home from work. It means well, it doesn't want to dry my face out but...I wish it could detect the smell of tired socks and choose to not waft said pungent aroma throughout the cabin

 

@EAST I will try few things per your suggestion tonight once I get back from work.

From what I remember when I turn head light on, both volume and tuner button doesn't work but I am able to use menu options or steering controls fine at that time. I am not 100% sure if heated/cooled seats button illuminate or not at that time.

I will double check all the fuses again (especially once you mentioned) but when I followed directions/fuse-map from fusebox.info site for the car, I didn't find any blown fuse.

It is for sure a mystery and hopefully we can uncover fast enough.

 

@EAST I confirmed that issue is only with the area of radio as I had highlighted with red pen in the image posted earlier.

Heated/cooled seat button illumination is fine and ambient lights, door wells, clock etc all lit up fine at night (or with headlights activated during the day) and just the radio area has the problem.

I will try to look at all fuses with help of my friend. Last time I tried crawling under passenger footwell area to access fuse-box and it was painful, my friend is skinny and flexible enough to get there :-)

 

Bringing over some of the other convo to get some more feedback.

For the 59 pin connector going into the radio the below table shows that pins 13 and 14 are the illumination pins.



So as example (marked in blue), you'd measure voltage between pin 14(illum+) and pin 12 (ground). If its easier, skip using pin 12 and directly measure ground (assuming ground and pin 12 test good for continuity). With the engine switch ON position and headlights off, you should read less than 1 V DC.
With engine switch in ON position and headlights ON or in Parking, that should read 11 to 14 V.

Similar for red. The way Lexus dims interior lights seems to be by pulsing the "ground" or negative side of the circuit. I would imagine the voltage value would change as you turn the dimmer switch. I would think that voltage between pin 13 and vehicle ground would decrease as you change the dimmer to make the lights brighter.

Even easier, if you have a low wattage test light, you could put it between pin 13 and 14 to see if it lights up and changes brightness. You might even be able to just measure between pin 13 and pin 14 with the multimeter in V DC and see if apparent voltage changes with dimmer changes.

Looking through at other illumination items, it seems the steering wheel lights share the same positive as Pin 14 (Illum+) of connector N162. But they don't share the same ground (so steering wheel button lights likely don't dim).


Looking at the circuit of the Remote mouse button illumination, the negative side goes to the same pin 39 of the Combination meter N40 connector that the radio pin 13 (N162) goes to.


Since you said that the lights of the remote control and other areas work, I'm making an assumption that if the positive of a shared circuit is working and the negative of a shared circuit is working, then power should be getting to those radio pins. Meaning, I don't think it's a fuse issue. It would likely be a wiring issue (maybe a broken wire?) or your radio itself has an issue.

 

If worse gets to worse, we cannot purchase a brand new OEM head unit.
Lexus does an “exchanged” Pioneer head unit for about $500.

 

Pin 14 is reading voltage as @EAST suggested while ignition is on and headlights are on. Its reading around 1v while headlights are off. All interior illumination lights working properly as we increase or decrease dimmer control. Didn't get chance to go through all the fuses once again as my friend had a very limited time.

I misspoke earlier that the issue happens during daytime with headlights ON (it was relayed to me by my son who drives car primarily). After I reconfirmed I found out that the during daytime, radio controls stay illuminated fine and those don't have illumination at night time only regardless of headlight on of off or auto. Is there anything that controls lighting automatically at dark?

I will be out on vacation for some time till early August so I will try to follow-up on this thread once I return.

Once again, THANKS to all of you who have been giving valuable advice.

 

@bayareaemt - I suspect it's the same ambient light sensor that controls your NAV screen (dark/black screen vs light screen).

 

@bclexus where do I find settings to adjust that? As far as I can tell Nav screen has been behaving fine