A month ago I replaced my door courtesy light (the ones at the bottom of the door panel) I recently ordered some Lexus logo lights and went to change them and noticed my rear passenger door LED was not on when I opened the door. After doing bulb changes and swapping the housing with a working housing and having nothing else work, I checked the voltage on that plug and it is reading milliamps instead of voltage. The other courtesy lights read at 12volts as they should. Any insight would be great, thank you!

Also, is there a multiplex door module per door for our cars?

 

First, milliamps is a value of amperage, not voltage.

My guess is that the door was left open and timed-out the amount of time that voltage is made available for the door courtesy light. If you close the door and reopen it you should have voltage available for the courtesy light.

By the way, the trunk light works in the same way - the light will timeout after a period of time when the trunk lid is left open.

 

​​​​@bclexus thanks for getting back to me. The light does not have enough power going to it when the door is opened. I checked the voltage, at the plug, right after opening the door and it reads milliamps instead of voltage while all the other doors show 12 volts. Are you familiar with the multiplex door module in our vehicles?

 

I am not that familiar with the wiring, but. Look for a Bad contact switch at the door for on/off - open/close. That's likely where its having problems with voltage drop with getting the 12 volts to the connector when cutting off then on. I always trace back from the connector to the battery, everything along the way in between.

 

@jgscott I have tried swapping the rubber contact switch with the front one to see if that was the issue but it was not. I will try to find the MPX module and see if I can order a replacement. I am seeing dome, door and courtesy light issues with the MPX module for other Lexus models so I guess I’ll try swapping that and see if it fixes the issue.

BTW, do you happen to know where the GS’s multiplex door modules are located? I am still figuring that out. Thanks in advanced!

 

It sounds like maybe one of the two wires feeding that particular courtesy light might be open (i.e. not connected or disconnected by some means).

The wiring for the door courtesy lights is very small gauge (probably just 18 or 20 gauge insulated wiring) and rather delicate. I believe some GS 350 models were made with the courtesy door light wiring not in a corrugated wire loom tubing behind the door panel whereas others do have the wiring in a corrugated wire loom tubing. You might want to check to make sure you did not break or pull out one of the wires feeding that particular courtesy door light, which may be a problem without removing the door panel for a better view and access. Then, you should be able to check whether there is 12 volts available with access to the two wires. If by chance one of the two wires is broken or pulled out you will need to splice or reconnect it to complete the circuit feeding the light.

I'm unaware of a multiplex door module, but there is some means of timing-out the door courtesy lights as well as the trunk light and killing the voltage after so many minutes. I believe the timeout period is ~20 minutes.

Maybe peasodos knows what means is used to timeout the lights if a door or the trunk lid is left open.

 

Ok good you know. That was step 1. So have you tried tapping before the switch, from the 12v? So the drop is coming before the switch?

Just to eliminate no custom Audio Sub ever installed or anything like that right? God knows why the day for a door light all that Factory stuff is needed for a constant 12v to a Courtesy light? Looking like it is the MPX. Get one that you can return if you can. Just in case. One of the Mod Guru swap Guys will come in the Thread soon.

 

Okay, so I am starting to narrow down the issue. I just realized for the door with the nonworking courtesy light, the car will not beep when I shut the door while the car is on. All the other doors beep when I open and shut the door while the vehicle is running. Anyone know if there is a relay or module for that or is it just the rubber push sensor located on the inner side of the quarter panel?

 

IDK, but you could disconnect one that works and see if it still beeps or not? If not you know it's the rubber push sensor. If it still beeps its something else.

 

Are you doing this (opening and shutting the car doors) with you outside of the car with the car On and/or with the engine running? Where is the key fob when you're opening and shutting the car doors and hearing the beeps?

The car will beep if you get out of the car with the engine running. There is likely a safeguard beep if one of the doors is open with the engine running and the key fob is outside of the cabin.

Just to satisfy my curiosity - Get out of the car and lock it (just like you and your passengers were going into a restaurant), then unlock the car (which I'm assuming you have setup to unlock all four car doors when you unlock the car) and open that door which you said the courtesy light did not work and see if it works now.

 

Well, just swapped the front rubber door jamb sensor with the rear and it still does not work. The car does not know the door is open so I am guessing there is a relay or the wiring for that sensor is messed up. I will take my rear pillar apart tomorrow and dissect more. If you know where/if there is a relay for the rear door, please let me know.

 

​​​​@bclexus So every other function for that door works properly, door handle light, trim light, lock, unlock and windows.. It is literally just the courtesy light and it is bugging the hell out of me hahah. Do you know if there is a relay for the courtesy light? I feel like there is a relay stuck in the close position because on the display on my cluster the door open animation does not show open when I do open the door with the nonworking courtesy light.

 

No aftermarket sub or anything installed. Just the stock ML system. I just tested the contact behind the plug and it read at 7 volts for a few seconds but went back to milliamps just like the front of the plug.

 

Well, if there was such a relay the contacts would be 'open' (not closed) which would prevent voltage from going to that circuit feeding the non-working door courtesy light. But I'm unaware of such a relay or any other component (e.g. module) that controls the door lights.

That really is a mysterious problem with just that one door.

How long has that light not worked? Or do you even know the answer since it's not a door you would ever use or pay any attention to, right?

Have you had your windows tinted since you bought the car? If so, how long ago? I would not be at all surprised to learn that the door light stopped working about the time the windows were tinted...but you might not be able to rationalize that time-wise if you cannot pinpoint when that door light stopped working. Sometimes tint shop employees are not real careful removing and reinstalling door panels and it won't be the first time that delicate wiring is pulled out of a connector or wires are ripped apart.

It appears that your next task is going to be to remove the door panel and have a look to see if you can detect why the plug end of the two wire harness is not supplying 12 volts to the door light. Hopefully you can find the problem right away once you have access to look behind the door panel. I personally can't imagine you have a problem with something like a module that has failed.

Answer these questions please, and also think about everything you have done to the car, and everything you had someone else do to the car - and think what may have caused this problem.

 

I do not have an exact date the light stopped working but the last time I knew it worked for sure is April of 2021 because that is around the time I got my vleds for all my interior lights and puddle lights. I only recently opened that door to replace the vleds with lexus logo courtesy lights. The rear doors were tinted a few years ago so it can not be that. Tomorrow I will remove the door panel again and test the voltage along the wiring. When I removed the door panel the other day everything looked good but I will take a closer look at the wiring.

I hope I can figure it out because now it bothers me, if I had never ordered the logo lights I would have left it alone for who knows how long hahah. Thank you so much for all the advice and help.