I have 2016 IS200T it’s barely 4 yrs old at 54k mileage. I don’t think I would have this issue if I properly wired my dash cam and not using the stupid knock off LED boards dome lights. I gotta admit. It was hella bright though haha.

 

I really hope you get this figured out, UngBuck. I'm crossing my fingers and toes for you!
This is why I let others install and repair things on this car and other vehicles. I'll be getting a dual
dash cam at some point and will pay the local auto stereo shop to install it, as they've done
two other cars. I know folks here have the skills to do all kinds of things.
Best of luck!!!!

 

After reviewing the diagrams for both the interior lights and the illumination lights, there is no real connection other than the junction block under the dash that holds all the fuses...which you checked the Panel fuse already.
The interior lights are powered by the Dome fuse, so a completely independent circuit to the Panel fuse.

The simple explanation here is that the LED's, in the components that have an issue, have simply failed.
Which sounds ridiculous because that would mean all 3 components had an issue at the same time...the AC unit, the seat heater/cooler switches, and the drivers door master switch.

Since the drivers door master switch is the easiest to access, would you be up for removing the master switch to check for power on the illumination G (green) wire?
I could likely find instructions on how to remove it.
Basically you'd be looking for 12V at the G wire once the tail lights are on. If you get 12 volts, then the LEDs in the switch are bad, and you need a new switch...if you get a noticeably lower reading, then there is an issue with the circuit, and potentially the switch is fine.
Even better if you know someone with an IS, you could just try your switch in their vehicle, if the lights have the same issue, then the switch is bad...if it doesn't then your vehicle circuit has an issue.

 

I wonder if those LED boards shorted out and fried another part if the system. When I approach my car at night, my interior lighting ramps up, and as I walk away, it dims down and then off. So the lighting is not a simple on/off toggle, there is some circuitry to ramp it up and down, so could that have been damaged by the add on boards?

 

sounds good. The door panel might be doable. I’ll give it a try this weekend. Is the master switch under all these buttons?

 

I also do think that the problem is the LED. But like you said, LED failed in 3 separate components like that is too much of a coincident.

Time to trouble shoot individual components.

 

That ramping up and down effect is controlled by the Main Body ECU.
The only issue with the dome lights is that it's on a completely different circuit that the illumination lights.
It would be like if the dome lights had an issue, and the brake lights went out...just not possible.
The only thing is though, in this case the Dome and Panel circuit are part of the junction block under the the drivers side where all the fuses are.
Attached to the block is the Main Body ECU...so if the Body ECU took a hit internally from the Dome lights, then it could have fried another unrelated circuit...which I really hope is not the case.
Also, for the AC control unit, all the LEDs are on the same circuit...without being able to see the internal circuitry, the assumption is that is something is happening to one bulb in the unit, it should happen to all.

 

The master switch is basically all the buttons and the part underneath you can't see.
The buttons come out with the trim panel around it...it's all just clipped in.
Start at the bottom and pop it out...I put an arrow in the pic of where the tool is in the pic...the pic is kinda busy.


When you remove it you will see the master switch is screwed to the back of the trim panel, and has one connector.

 

It really depends what the person's background (easy for me to say for I pretty much a wanna be jack-of-all-trades guy). Not judging the OP or anybody here, but sometimes you never know. You could be the best electronics engineer, but if the product you bought is defective, then what.

There are ways to prevent them by not installing the add-ons on-the-fly, but testing them first before installing.

I always break-in dashcams for a week at home, making sure all the functions I need are working well before installing it my cars.

 

Thanks. I found on YouTube on how to remove the master switch. It’s very simple. But I have no clue where the G wire is. How would I test the voltage? You said if I get 12V with tail light on. Then it’s a bad switch. Isnt it the other way around? I would get 12V because the battery supply the voltage when the tail lights are on?
I went back to your ILL.PDF wiring diagram. I see that the master switch is N18, N27. I'm going to stick the red into each of the pin of N18 and black to ground to a bolt on the door jam to test the voltage. Is it Pin 3 & 8 for G wire? I see 3 for A and 8 for B.

 

The test you will be doing is with the Master Switch (we will call it MS for short) disconnected. You will be checking for 12V at the vehicle harness connector.
See below:
If you have Memory Seats, then the connector at the MS is N18 (total 20 pins) which is white, and the G wire is in position 3.
If you do not have Memory Seats, then the connector at the MS is N27 (total 22 pins) which is black, and the G wire is in position 8.



For the explanation, I will assume you do not have memory seats, so you will be working with black connector N27 pin 8 (the G wire).
Step 1 - Disconnect the MS...put it aside
Step 2 - Set your meter to 20V and attach/touch the black lead to Ground...the door striker is perfect (it's exposed bare metal and right there at the door jam)
Step 3 - Turn the Tail Lights on
Step 4 - Touch the red lead to N27 pin 8 (the G wire) - if the opening in the front of the connector is too small for the tip of the red lead, then go from the back of the connector...or...stick a paperclip in the front and touch the red lead to the paperclip)
Step 5 - Read the meter...if it's battery voltage (12V), then the power circuit to the MS is fine and likely the LEDs in the Master Switch are bad...if it's less than battery voltage, then that means there is not enough voltage being supplied to the MS, therefore the LEDs may not light properly

You can also check to see if the LEDs are working on the switch when it's not plugged into the vehicle.
Basically you are trying to light up the LED circuit, so if you apply Power and Ground to the proper pins on the MS connector when it's disconnected from the vehicle, you can also make them light up.
Assuming we are working with an MS that has 22 pins (connector N27 on the vehicle side), you would supply 12V to pin 8 (which is the corresponding G wire on the vehicle side) and Ground to pin 6 (which is the corresponding BE (Beige) wire on the vehicle side).
All this will do is light up the LEDs on the switch. If you have some spare wire to use and some paperclips, that would make it easier. You could use the car battery as your power and Ground.

 

hey,
im also having the same issue but every single backlight doesn’t work in my rc. When the headlights turn on, nothing inside the car illuminates besides the screen and gauges. Where exactly is the fuse for the interior backlight?

 

The interior illumination is powered by the 7.5A PANEL. The fuse is in the driver's side fuse block under the dash on the left.
The block has 3 rows of fuses, the PANEL fuse is in the middle row right about the middle.
If the fuse is blown, then the next question is why.

 

Man I got left on such a cliffhanger. I started reading the thread and I got really excited to see if the problem was resolved, and then all of the sudden, the thread just died...... You're the man though Sasnuke