Greetings. New member here and a new to me 2023 GX460 Premium CPO.
I recently noticed that the convenience lights on both my running boards do not operate and I don’t recall if they ever worked. All the interior convenience lights properly turn on when I approach my vehicle with my fob or using the fob to unlock the doors. Since it’s still under warranty, I had it in the Lexus Service to have it checked out. The technician spent 1-1/2 hours trying to determine the issue but was unsuccessful. They’re going to do some research and asked me to make another service appointment. The curious thing is that there’s power running into the bulb sockets but won’t light up the bulbs. Fuses and bulbs checked out good.

I’m hoping someone can provide some insight on what the issue is and possibly suggest some next steps to try.

Appreciate any and all advice.

Cheers!

If you have power to the socket that is half the circuit, was the ground checked?

Good point! I’m not electrically inclined so I’ll have to mention it to the Service Tech. Thank you!

strange, lexus service will have access to the troubleshooting and should have been able to determine the root within 1.5 hours.
if theres power to the bulbs, then placing in a functioning bulb will light the bulb. this also shows that the detection side of the main body ecu functions and that the ecu also functions. i cant imagine them checking power at the positive side of the socket and then the negative side not at the socket. there are simple adapters used for these checks instead of meter probes.
certain bulbs have polarity which needs matched.
if it is the case that they checked only the positive side, or that they meant that the negative side is open, theres only one or two junctions that need checked if the negative socket side to negative (aka gnd) shows open on the meter.

one thing overlooked and not in the service manual is to check for pushed pins, either at the ecu or any junction with pinned connectors.
it can be that the pin is not locked into the connector at the ecu, when the harness gets installed the unlocked pin gets pushed back into the connector, just barely making contact and later vibrating loose or maybe not even making contact at all. Final OK at factory or a gate quality check earlier will check functionality so at one time it did work.

Confirm bulbs in sockets are original spec incase the previous owner replacement them with something else.

it should have lights. dont know why. but should be an easy fix.

This is the odd part. What voltage did they measure? If they tested voltage at the socket (using the socket for negative as well) then the circuit seems fine - but if using a random metal ground for the DMM, then yes - the circuit ground(s) should be checked as well.

And are they incandescent (non-polarized) OEM bulbs? If they were LED's - they can test good, but if installed backwards they won't illuminate (or if the ramp up / ramp down dimming/voltage is not reaching the full 12-14v, then LED's might not illuminate at all).

You've been given excellent advice here. Lexus could not find the problem? They want you to return? Find another garage to fix your car. I would never return to that dealership. Look for a competent garage.

What kind of terrible tech at a dealership can't figure out why a light bulb isn't coming on?

Lexus service had my GX two more days to continue diagnostic of my running board lights issue. They eventually sent a TSA (Tech Support Assistance???) to Lexus engineering and finally after the next morning they fixed it(?).

On my service work order, the technician added the comment “Found Customized Setting Turned Off - Turned Setting On, Verified Operation”
Can anyone tell me where that Customized Setting is. I checked Vehicle - Light Settings and went through it several times and couldn’t find it there. I’m sure the service technician went there too and couldn’t fix it either. Now I’m wondering if that setting was is in the ECU and accessible with TechStream only?

Is this similar to the option of welcome lighting?

Yes. aka convenience lights, courtesy lights etc…
All the interior lights turn on when I approach the vehicle with my key fob. Only the running boards were the issue for me. Fixed now!

Didnt know you could select which lights to turn on for welcome lighting. @Acrad might be something to add on to your excellent MY guides?

I now realize that the “Welcome” illumination for the running boards are actually in the Vehicle Customization - Light Settings - Exterior Lights Auto-off Timer settings. It doesn’t mention “Welcome” lighting but it’s the setting for all exterior lighting timer settings. I guess the service technician didn’t realize that either. Issue now resolved.