LexusGSboy

2016 F Sport - just under 70k.

Last night early in the evening I thought the tail lights of the car looked like they were on (the one basically on the side of the light in the quarter panel). I hadn't driven the car in a couple of days and don't remember seeing them on on Sun/Mon. I figured it was just way the evening light was hitting it.

Today I walked out to take something out to the another car before leaving on an errand and realized the lights were indeed on. Today is trash day and last night I took out our three containers and even took some things out later and never noticed the lights (it was dark by this point so I don't see how I could have missed them - I'm usually very aware of things, but maybe???)

Car was locked so I went and got the fob. Tried to open the trunk with the fob and it didn't open (tried 2 times). Unlocked the car, relocked the car - lights were still on and flickered occassionally (like getting brighter/duller).

Unlocked the car, started it. Tail lights still on with no other lights on. The high mount/center brake light was not on.

Turned the car off, checked the light switch - set to Auto. Checked the brake pedal - pushing activated the highmount/center brake light as well as the normal brake lights. Turned the light switch all the way off (DRL Off). Tail lights still on. Popped the trunk with both the button near the license plate - worked fine. Popped it from the button inside - worked fine. Tried from the fob a another time - worked fine.

So....
It doesn't seem to be a stuck brake pedal
It doesn't seem to be the light switch in the wrong position.

I looked in the opening inside the trunk - it seems dry and fine inside there.

I did wash the car Saturday morning (was going to post that under the what did you do today) but I don't remember the lights being on at any time while I was washing or drying the car. Took a photo of the car from the side to use in a post and the lights do not appear to be on in that photo - taken 4-5 hours after the car was washed - car was not driven since.

We've had a few decent days of rain so that's sort of my first thought but still seems odd.

Another note - battery was replaced by the dealer about a month ago. The car had the original battery I believe (with the plugs in the holes, not the removable caps). Part of the reason for replacing it was because if the car sat over a weekend it would labor to start on Monday but again - it was 7 years old and had almost 70k on it so we didn't really do any diagnostic on things.

Any thoughts on what could be going on or what could fix it? I'm sort of stumped. I've thought about pulling the battery connector for a few minutes then re-attaching to see if that resets something - although again, no idea what that "something" might be. Only other thought would be an exorcism....I mean we are getting close to that time of year.

Thanks in advance!

LeX2K

Try to shift out of park without pressing the brake pedal.

LexusGSboy

It would not let me shift at all without pressing the brake pedal.

Also tried shifting to neutral, manually setting the parking brake, turning the car (engine) off, moving the shifter to P, turning the whole car off (second push of the start/stop button).

Still no change.

LeX2K

That means the brake light switch is working. Pulling the negative battery terminal for 10 minutes is a good idea.

LexusGSboy

Disconnecting the negative terminal for 10 minutes didn't solve the issue either. Chatted with my service advisor at Lexus and he hadn't seen anything like this. It just seems so weird. I would assume the wires to the taillight have zero power in them if the switch is off, the car is off, and the break pedal isn't being depressed so it seems weird that something could/would be completing the circuit.

LeX2K

I'm guessing here but it sounds like the microcontroller in the tail light has failed.

FullMetalM

If you press the brake do they come on brighter or are they on the 'parking light' brightness. Do you have separate blinkers, or is it using the brake light as a blinker?

Its almost certainly a wiring issue. I dont know for this car specifically but having power going through a wire, that only actually turns on when it is grounded is pretty common. So if a wire is exposed and grounding to something else that could switch it on.
first place to check is the tail light plugs. Your going to need to pull the boot liner apart a little so you can check the connections. looking for debris or water etc.

LexusGSboy

The brake light portion of the lights is not on - just the "normal" tail light portion. Depressing the brake pedal makes the brake light portion come on as normal on both sides as well as the center brake light.

All of the rest of the lights work as they should (turn indicators, reverse lamps)

Boot made me laugh a little - which is good right now as I'm imagining the very expensive diagnostic time trying to track something like this down. Also made we wonder what other parts of the world calls a front trunk (or furnk) on cars that have them? Front boot and rear boot?

There's a cover the twists off where the connector to the tail light is - I opened that earlier and it seems connected properly and it seems to be bone dry in there. I haven't pulled more of the liner apart to dig around.

I'm actually headed out of town on business so don't have time to get it to the dealer or dig too much and I'd rather folks at the house not have to keep starting/driving the car so the battery doesn't completely drain before I get back. One thought was to pull the fuse for the tail lights vs disconnecting the battery but looking in the manual there seem to be 5 separate fuse boxes LOL. Two in the engine bay, one under each side of the dash, and one in the trunk. The manual, from what I could find, doesn't show where any fuses are - my guess is that you have to look at each fuse cover and it tells you.

Looking online I THINK the tail lights are in Engine Compartment Box 1, Fuse 6. Is there anything I'm not considering in terms of pulling the fuse vs disconnecting the battery? Obviously I won't drive it that way. The main concern I have with disconnecting the battery for a long period is losing information/settings. I know those things survive a 10-15 minute disconnect - but what about a multi day disconnect?

FullMetalM

Lol, yeah Trunk is not something we use in Aus. We never use 'front trunk', people would probably say bonnet, frunk or front boot haha.

I agree that pulling the fuse is a good option as opposed to the battery, I don't know what fuse that would be to help you. I would even consider just disconnecting the lights, that might be easier. Just make sure that anyone that might drive the car knows haha.

lex2k says it could be the controller in the light housing. Things like that usually dont fail but if was gonna fail i would say water. So check around the light as much as you can see if the seal is damaged etc.

LexusGSboy

So went out really quick to look at the fuse boxes in the engine bay - didn't quickly find which one it was so I'll need to research a bit more on that. Found the spot in the trunk - man, that little door is completely useless - you can't see in there at all.

One new bit of info now that it's dark - the LEDs on the license plate are also on. I'll likely just disconnect the battery for the night.

EAST

Just to make sure I understand, both pairs of lights (A and B in picture below) are on? And both sides (driver and passenger) are on? Are your plate lights on as well (reflection, C in picture)? At least in earlier years, all those lights were tied to the same circuit.

Are they the same brightness as when you have running lights on? As in is there any change in brightness when you switched through the light modes?

I quickly checked the plug to light A, and it's only 3 wires. Likely a High/stop, low/running light, and ground but would have to measure it.


Note: picture is of lights when you unlock the car and the DRLs and rear running lights turn on.

EDIT: I see you posted before I finished, so yea seems something upstream is giving you power.

FullMetalM

Only other thing i can think of is a sticky relay. Which honestly would probably be a nice issue, shouldn't be hard for a tech to test that for you. Next question is are the DRL on their parking mode or DRL mode, do they change when the stalk goes from auto to parking lights.
If they are on and dont change, that suggests the car just has parking lights on and would lend a bit more credence to sticky relay. whatever it ends up being, I hope its not expensive for you.

jgscott

iTrader: (1)

Trying to follow here. So sitting parked the Taillights are on, like now? Except disco the battery they won't turn off at all?

If the above is the case. Something is feeding a constant voltage to the tails. The problem with that is 2 things control the light switch and breaks the circuit for the tails. One is the inside stalk light switch. So the circuit is broke for voltage to the headlights, but not to the taillights.

My next thought is about the problem you had with the remote trunk lock not opening? Which lights were flickered, Tails?

My 1st thought was the Remote lock/unlock blinks the Tails, maybe it got a short or failure at that module, but such a module would have to feed the Tails, Front amber and Mirror turns all separately, because they are not staying on also?

I would play around doing lock/unlock with the remote many, many times and see if something changes? I may be wrong but my guess is that when you hit the remote to lock the doors and the lights should blink sending voltage then cutting it. Something is Not cutting the voltage to the tails? When you hit the unlock remote button the Tails they do normally light up staying on for a min. The Tails, Mirror and front amber should all light up on Unlock. Something is keeping the Tails from turning off. I think it's Security remote related? I hope that was not confusing enough. I also could be wrong.

LexusGSboy

@EAST To confirm - yes, A and B on both driver and passenger sides are on. C is on also (during daylight I hadn't noticed that). When I first noticed them they seemed to sort of go a little bright and a little dim but that doesn't seem to be happening at the moment.

The tail lights don't appear to change based on any of the switch positions on the light stalk. Putting the switch in DRL Off does nothing to the tail lights. Otherwise, the light switch works as expected.

@jgscott correct - other than disconnecting the battery, nothing turns those lights off.

All other lights, headlights, front turn indicators, rear turn indicators, brake lights, reverse lights, turn indicators on the mirrors work as expected.
All lights flash as expected when locking/unlocking the car. Note that on the tail lights its the amber lights that flash, none of the red flashes. The front lights turn off after the normal delay when locking the car.

When I took the car out it was starting to get dark and the head lights came on as expected for the Auto setting.

I'm still trying to track down exactly which fuse it is - The fuse boxes under the hood are easy to access but the ones under the dash and in the trunk are near impossible to look at/get into.

EAST

EDIT: Please see post 18 for update clarification, as pins/wires listed below may not be applicable to a 2016+.

This is more for when you go on to troubleshoot this, but here goes. If you open the fuse box in the engine that looks like the picture, you'll see the "integration relay". It's the whole center slim box. This is where some relays are found. You can take out the unit with a flat head. You pry the two tabs outward (general area marked in red). You can start with one side, and pull up a little on the box, then move onto the other side. It will slide up. Make sure to gently pull up the wires to give you more slack.​​​​​​


You'll see 3 plugs. I marked them as they are known "2A, 2B". 2G is off to the left, but not important for this. EDIT: THESE PIN NUMBERS ARE FOR A 2014 (preface-lift), AND MAY NOT APPLY TO A POST FACE-LIFT.
Pin 16 (the skinny red wire) of 2A should be the control wire, which comes from the multiplex body ECU.
Pin 2 (the medium thicknesses green wire) of 2B should be the wire the actually powers the tail circuit.

​​​​​​I say "should" because I didn't measure them, just going off the circuit.


The cover of the relay module felt like it could come off with some messing around with screwdrivers, but I didn't want to chance it. You could definitely hear relays in there as you unlocked and locked.

I would say order of operations would be to try to take the cover off the module to see if it's possible to track down which relay corresponds to the pins above. If yes, then seeing if that relay could be removed. Then you could see if something is telling the relay to engage (control wire being 12V when it shouldn't), or if it's possible the relay is getting stuck.
​​​
One observation... while the integration relay module as a whole was out, the tail lights would not turn on, even if the DRLs did. Along with the 3 connectors, there seems to be a blade connector that is part of the module as a whole. Without opening up the module, I don't know what all that blade connector powers. The thick red wire in connector 2B should be a battery connection, so unsure if the blade connector is a secondary power connection or what.