LexusGSboy

I found this online that seems to indicate which fuse should be the rear tail lights:





But opening that fuse box this is what you haven....




It is labeled P/I ALT but it's a 100amp, not an 80amp according to the note on the cover. Maybe that changed with the '16+. But - those four fuses seem to be some big module - not individual fuses and that module doesn't seem to easily pull out. I'm also not exactly sure what that module thing is. Also, pulling that out as a block seems to impact a whole bunch of other things according to the first chart above (number 4-7).

So....it looks like simply pulling the fuse for the tail lights isn't as simple as hoped.

I had the battery disconnected for over half an hour and that didn't seem to help.

LexusGSboy

@EAST - thanks for all of that info! When I get back I may look into that a bit more. Since I need to get packed and I can't simply pop the fuse for the tail lights I've gone ahead and just disconnected the negative terminal on the battery. I guess I'll find out what holds in memory after the battery being disconnected for a few days. When I chatted with the Service advisor earlier he said it shouldn't be a problem over all - although hopefully most of that data is stored in a way or has some sort of aux power that holds for a few days. I don't care as much about Radio presets - more about the Trip A and Trip B ODO and the fuel consumption history and other data like that. I should have taken a few photos but it won't be the end of the world if it gets lost.

EAST

Alright I went through and wrote down all the pin outs given in circuit for the connectors. The circuits are for a 2014. But looking at the numbers and the picture of the wiring, some things don't match up to wires found in a 2018 connector... so the green (pin2) and red wire (pin 16) I mentioned above may not actually be for the tail circuit for a post facelift GS. I'll update my post above to reference this post.

All that can really be said is that the integration relay could be disconnected since it seems to only deal with lighting (fogs, tails, stop, high beams). Maybe one day if I'm bored I'll scope them out to try to piece what goes where.

Picture of connectors from a 2018 (post facelift)


Integration relay connections for a 2014 (preface-lift) that I could find. Horn, low beams, washer, turn/hazard lights all operate through their own circuits.
2A connector
1 - Left Headlight highbeam output
2 - Right headlight highbeam output
3 - Taillight Stop and 3rd brake light output
7 - ACC (from skid control ECU)
9 - DRL Right output
10 - DRL Left output
11 - Stop light control input (from stop light switch assembly)
12 - DRL control input
13 - Headlight high beam control input
15 - Fog control
16 - Tail running lights control input
18 - ESS (from skid control ECU)
22 - Ground A

2B connector
2 - Tail running and license plate light output
3 - Front Fog right output
7 - Batt
8 - IG1A
9 - Front Fog left output
10 - Ground B

2G
1 - Alt

LexusGSboy

@EAST Thanks for all of that! I'm a bit at awe about being able to track that all down so quickly and knowing all that went in to figuring that out. I likely won't have time before my flight - wish I could just yank that greenish wire from the 2B/2 output location until I get back but I'm guessing it's not quite that easy to just pull it out.

I've thought about this more and looked at it after dark quite a few times and determined there's no way I could have walked by the car as many times as I did at the times of day I did on Sunday/Monday/Tuesday and not have seen this and the car wasn't driven after I pulled it back into its space after washing it Saturday morning. I may have hit the lock on fob Tuesday night just to check that it was locked - not 100% on that. But on Wednesday morning the lights were definitely on after pretty much no interaction with the car for 3 days.

We had lots of rain so part of me thinks is water related but we always have lots of rain in Oregon so it seems very strange. I felt around inside the trunk liner through the opening where you access the connector to the tail light and inside there's some insulation that all feels dry. Noticed what seems to be a drain tube inside the cover for the fuses in the trunk and it seemed dry also - I could see surface tension pulling water down that tube if it were plugged or somehow got disconnected.

Part of me hopes that when I get back and reconnect the battery the problem goes away - although I know that just means it'll come back at some point probably.

jgscott

iTrader: (1)

I can't see it being a fuse. That would break a connection 99% of the time. Not hold current to pass through.

EAST

I'd almost say you could pull out all of connector 2B, and that should remove any power going to the tail lights. But it would also remove any power going to other lights/items.

I'm hesitant to say it's the green wire in pin 2B/2 for sure, without measuring. If it counts for anything, though, there is a green wire in 2B/2 in the older relay module . So maybe it is the tail light circuit.
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I'd venture to say your issue is as @FullMetalM mentioned and it's a sticky/faulty relay within the module itself. Without opening it up, we can't tell if they are user replaceable.

Your troubleshooting will basically end up being:
- if removing the actually source of power (connector 2B) turns them off when you put the module back in, then you know the issue is more "upstream" (relay, or control of relay). If they don't turn off, then you know something is giving power to that circuit downstream (and would be more a pain) and you'd have to find where.

​​​​​- then you try to determine if the wire that controls the relay for the running lights is correctly going high and low when it should.
If yes, then that narrows it to bad relay (or something causing the relay to think it's being triggered high, like conductive debris or water shorting the coil to 12V, causing it to engage)
If the control is remaining high, them that takes you further upstream to see what is causing that wire to remain high.

As a side note, looking at the wires from a relay module from a 2015 GS on ebay (part number 82641-30340), at least connector pin out for 2B matches, and some of the wire color positions match (I know it's not good practice to assume same color equals same wire). But 2A has some wires that make me thing there are other systems using that relay module that I didn't list above.

82641-30340 (more closely matches the pin out above)


vs the 82641-30320 that I have in the 2018.




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jgscott

iTrader: (1)

Didn't I see in other post that you are still under a extended warranty still? I am still for just this reason. If so and was me. I would just take it to the shop, pay the deduct if there is one, and know it's resolved. Too much electrical going on in these car. A ECU just to roll down the windows. lol! Plus, that's a weird problem.

LexusGSboy

I wasn’t thinking it was a fuse, I was hoping the fuse was a quick solution to turning off the lights until I could deal w things. Just ended up disconnecting the battery until I’m back in town so the family didn’t have to deal w it

LexusGSboy

It is under extended warranty but from what I was told there are situations w things like nature (rodent damage, water issues) that wouldn’t necessarily be covered.

That’s where it gets tricky, I could take it in, they could spend a few hours trying to track down the problem then to only discover that or falls outside the warranty. It is Lexus and my advisor is good so I’m relatively confident they’d try to cover it if it’s at all possible but it’s a bit of an unknown.

Being a relay or something would be awesome because then it would be covered

EAST

Ah my guy, I'd just take it to Lexus then (when you come back in town). As much as I've enjoyed the investigation, it would suck to break something like a tab or wire/pin when it could potentially be under warranty.

They'd have access to the correct circuit, which would cut diagnosing time considerably in checking if control signal is turning on and off. You checked the rear for wetness, and you would have seen wetness in the engine fusebox area (the driver side one with the Integration relay).

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GSJ350

Has anybody mentioned to check the detent switch or the actual mechanism on the brake pedal itself? If you get down and look at the brake pedal assembly and while pressing the pedal down you can see a blue piston that moves in and out of a sensor. If the detent switch inside that sensor is stuck, it would create the issue of the tail lights being stuck on. Ive had to replace one in another car (97 honda prelude) i owned some years ago. That would be a easy fix if it was the case 👍🏻.

jgscott

iTrader: (1)

It's is normal lights on Tails staying on. The switch depressed at the brakes would be.... the Brake lights. See op's 1st page post #8.

AJLex19

@LexusGSboy just curious: did the dealership figure out the issue with your tail lights?

bclexus

@LexusGSboy - Any aftermarket lighting or lighting related mods? Remote start?

Is a door left ajar? Trunk lid ajar? Gas tank door open?

Automatic light off system:
● When the headlights are on: The headlights and tail lights turn off 30 seconds after the
power switch is turned off and a door is opened and all of the doors and trunk are
closed. (The lights turn off immediately if on the key is pressed twice after all the
doors are closed.)
● When only the tail lights are on: The tail lights turn off automatically if the power switch
is turned off and the driver’s door is opened.
To turn the lights on again, turn the power switch to ON mode, or turn the light switch off
once and then back to or .
If any of the doors or trunk lid is kept open, the lights automatically turn off after 20 minutes.

For whatever it's worth:
The glove box light turns on when the tail lights are on.
The console box light turns on when the tail lights are on.

bclexus

@LexusGSboy - If your tail lights are actually flickering - there are two conditions that can cause it. (1) Oftentimes aftermarket LED lights will react by flickering or clipping when the current limiting resistor is not properly matched to the LED circuit or if the tolerance of the resistor changes significantly due to it overheating, or (2) if the flickering lights are filament lamps a bad or loose electrical connection or socket can be the cause.

But since your tail light problem is that they remain On, the two above noted conditions being your problem are remote, at best. I've never heard tell of the problem you're having with your tail lights.

Brake lights remaining On due to a defective brake pedal switch - yes - but you say it's the tail lights (not the brake lights) that are On.

Have you tapped into any circuits for a dashcam or rear-mounted camera? Any work done to the windshield or front facing light sensors that control any light whatsoever (e.g. for Auto headlights, for the instrument cluster, for the Auto High Beam headlights), etc.?