Weird Dome light issue for just Drivers side Front and Back doors

So, I've researched a ton, and I'm stumped. On my 2014 4Runner, my dome light inside the cabin quite coming on when it is switched to "door" setting. It will come on if I switch it to "on", so I know the bulb is not burned out. No doors will trigger the dome light to come on when opened. Just in case, I replaced all the door switches and nothing changed.

When I open up the passenger front door, passenger back door, or the hatch door in the back, the "door ajar" light turns on on the dash. If I open up the driver's front door, or the driver's back door, the "door ajar" light does NOT turn on.

Remember, I've already changed all the door switches out so that's not the issue.

I've check the fuse box under the steering wheel, and the "dome" fuses under the hood, and everything looks fine.

Like I said, I'm stumped, any ideas?

 

Does the courtesy light on the door turn on ?

 

If "courtesy light" is the light that is on the footer of the actual doors, then yes, all for doors work when the doors are open/closed as they should.

 

Is there a main fuse for that driver's side run of the door wiring??

 

Have you looked closely at the dome light switch ? Perhaps take a meter to it and measure.

This is an odd issue.

 

Still can't figure this out. Maybe some more background will shake something loose. I need to jump my car after the battery went dead. Immediately after I disconnected the cables from the battery and got back in, it smelled like ozone in the 4runner, like something electrical fizzled out. ideas?

 

Did you read post #5

 

Yup, I read it. What points are you suggesting I read between? If it's the dome light itself, that's simple, I get nothing across the light bulb when the door is opened in auto mode. Do you have any suggestion anywhere deeper to try?

 

I’m suggesting to remove the light switch and measure inside. You stated the dome light does come on, but not when the door is opened. Makes me believe it’s a setting issue on the switch. Tittle from off, always on and on only if door is open. You can measure continuity when the light switch is out of the truck.

 

All dome and door lights, and the door ajar light are controlled by the main body MPX ECU that is part of the cabin fuse box. There is a smaller square black plastic ECU attached to the side of it. If you are not getting the dome to trigger, and the 4R is not sensing doors open on one side, then it's the culprit. Have you tapped into any wires behind the dash in that area?

Combine those conditions with the fact that you mention the smell of ozone (never good when electronics are involved), and the MPX is probably cooked. Replace it, either new or used.

-Old Red

 

VERY interesting. I'm checked every fuse and relay in both fuse boxes and they were all good, so it was driving me crazy. I did not check the MPX though, so I'll do that next. Thanks for the good ideas!

 

If I remember correctly, all the inputs from the doors to the MPX are in the middle connector of the three. Start there checking the wiring for obvious signs before removing the fuse box to get to the MPX ECU.

 

I didn't realize ECU's (used) are $100+. Well, that sucks! So I took a picture of the area, but didn't see any issues with the wiring, so that was a bummer. You are saying the circled area is the connector in question, correct?

 

Yes, that’s the connector. No signs or heat or discoloration. Does anything smell burnt near the MPX or fuse box? Used is not too bad. New they are like 450-500.

 

How do I remove the two cables to the left of the highlighed square? I got a replacement MPX but I can't get these two cables out.

 

Towards the top of the two connectors in there will be a little black plastic tab in the black retaining lever. Press that down while gently pulling out near the top on the black plastic lever. It will swing out, and the connectors should come out easily. Installation is as simple as pushing the connectors in and pushing the lever back into the lock position.

 

Bah, I didn't see the black tab! Well that was easier than I was expecting.

 

Ok, so updates. I changed out just the Black box part of the MPX with the remainder being my stock unit. As soon as I plugged in the cables, it started smoking something fierce, so I quickly took out the wires. Obviously, the white part of the MPX is the main issue. So I took out the whole unit, and replaced it with the replacement I had. Funny thing is the driver's side passenger door is fixed now, but not the driver's door. I then swapped out the driver's door switch with another with another working one, and there was no change. I'm worried I fried something when I had the new "black" mpx in the stock "white" mpx holder. Thoughts? Pics below of the stock unit upon further inspection!

 

Good lord batman! So something is obviously shorting to ground. To clarify the white fuse box and MPX pictured above are the originals that weren't working, not the replacements? What does the inside of the new MPX look like? I am assuming burned as well, same area?

The burned pins are 1-4 on the fuse block and MPX. Pin #1 is Ground. Pin #2 is FLCY (Connector 2F #27) which is to the Drivers Door courtesy light switch , which triggers the dome light and light in the lower door when opening, and the door open indicator in the cluster. You have a short occurring when the door courtesy light is closed (door is open) which tells the MPX to ground pin # 1 on F8 (Pink wire, ground for courtesy light in driver door) and have more current going to ground than the MPX can handle . See the diagrams I attached/uploaded. Pin #1 on F8 and Pin #1 on the MPX connector are grounds and are burned the worst. The short is occurring at the driver door light with the bulb or wiring. Do you have an oem bulb in there, or is it an aftermarket LED?

 

Great information! The bulb in the dome is the OEM bulb. You are correct, those are the photos of my stock MPX that I pulled out. I didn't get a look at the guts of the new black MPX though. I should have. I can always pull it out later if you think that will help. I wish these things were easy to get in and out!

 

Sorry, should have been more clear. Not the dome light, but the courtesy light in the lower door panel. OEM or LED? Check the wiring to see if it is shorted. Unplug the light and check the pink wire from the connector at the light to the pink wire on connector F8 #1 for continuity. Then check the red wire (+) from the light connector to the pink wire on F8#1. If there is a short you will see continuity. No continuity means no short in the wire run, and the bulb is suspect.

 

OK, pulled it back out and inspected the board. There is a little burn marks and a pulled up tracing, so I did a little soldering and fixed the connection. Problem is, no change to my driver side door light. Ideas?

 

Diodes D022 and D024 are toast on the top side of the board. Repairing the trace won't do anything if other components in the circuit are bad. That MPX is done. You need to trace the wiring from the driver side door light to the Fuse Box and MPX. Something is shorting to ground between those points, and replacing the MPX without finding the short will just keep frying good ECUs.

Keep driver light bulb unplugged and battery disconnected while doing #'s 1-3

1) With F8 & 2F Connectors Disconnected from Fuse box & MPX, Test From F8 #1 To I7 #2 for Continuity on Pink Wire. (Continuity = GOOD)

2) Test entire length of Red wire From 2F #27 to I7 #1 (Continuity = Good)

3) Test 2F #27 to I7 #2 (Red to Pink) and F8 #1 to I7 #1 (Pink to Red)

3A) Continuity = BAD: If continuity between red/pink with no bulb hooked up, wires have shorted. Look between I7 to IF1 and IF1 to 2F and F8 to find location of the short and repair


3B) Open = GOOD: with battery disconnected hook bulb/light back up and test #3 again to see if bulb is culprit.

 

I'll run your tests tomorrow and report back. To answer your previous questions, the courtesy light was an aftermarket led light. I've actually changed all four of my lights to these Chinese ground projection-logo light things (which are pretty cool). All of them work except for the driver's door. I unplugged the driver's courtesy light and replaced it with the OEM one, no change...still dark. I think went to the driver's side rear door and swapped that working courtesy light with the one from the front that I took out. To my surprised, it flashed once, turned off, then started smoking. I yanked it out as fast as I could, replaced it with the working light, and it was back working just fine. So, the light from the driver's door is bad....even though i don't know if it's bad bc it's the "cause" or if it's bad and it was just collateral damage. I'll get back with you about the test above. Man, I wish i could just buy the circuit board instead. I really don't want to drop another $100+ on this just for a light.

 

Well that confirms my suspicions. Bad light shorted and caused the MPX to cook. I would remove all of those lights and chuck them in the trash. They aren’t worth frying ECUs.

I’m not a betting man, but I would put a $5 on the wires to the front door light probably being ok. Report back with what you find. Still test them to confirm, but new MPX and some factory bulbs or quality LEDs and you should be back in business.

 

Disconnected battery, unplugged connectors and tested with a multimeter. I'm having issues with the red cable. Have testing each spot from your diagram, here is what I found (for the red wire):
Full Red Wire Run: I7 #1 to 2F #27 = No Connectivity
I7 #1 to IF1 #6 (Driver's Side) = Connectivity
IF1 #6 (Driver's Side) to IF1 #6 (Cab Side) = No Connectivity
IF1 #6 (Cab Side) to 2F #27 = No Connectivity

Pink wire is great throughout. Then Rehook battery up and OEM courtesy light is "working" aka getting continuity when testing Red to Pink.

 

I made a typo, my fault. See the diagrams I posted. The results you indicated are correct testing from I7 #1 to 2F #27. Instead of I7 #1 it should have been O5 #1 (Door open switch in the jamb) to 2F #27. This should have continuity. Next, with the battery hooked up and no bulb in the courtesy light socket, measure I7#1 for 12V with respect to the chassis ground. If 12V are there then you should be ok wiring wise.

 

You’ve experienced a pretty common problem people have when replacing these door bulbs (usually with LEDs). If you don’t take apart the bulb housing cover to see what you’re doing, and you just start installing the bulb by feel, you can inadvertently short the leads together in the socket. And if you didn’t disconnect the battery first, and the door is open, the socket is powered with +12V from the ECU, and you fry the ECU.

The contact region of some cheap LEDs look like little circuit boards with lots of exposed metal and they can be rather thick, so it’s real easy to push them into the socket at an angle and smash pins together and create a short. Since there’s lax quality control and no pre-testing of these parts, they can be shorted right from the factory, or just have crappy construction and fail shorted.

In the future test all of your bulbs electrically before you install them. You can use a 9 volt battery. The Philips 168 (168ULWX2) LED bulb is a good reliable candidate for the door lights.

 

Alright, just ordered a "second" ECU. Now that the Chinese lights are out of the car, everything should be good again. Not looking forward to dismantling the car again in the Texas heat again though. Wish me luck...

 

Great news! Just installed my second ECU (stock burned up, 1st replacement burned up, now 2nd doing just fine!) and everything is working perfectly. So to sum up the root cause, Old Red was right, the issue was my Chinese aftermarket projection courtesy door lights. It's a shame because I loved them, but in the end, bad wiring causes (a minimum of) hundred dollars worth of damage. For reference, here is a link to the product: https://www.aliexpress.com/item/32897374186.html?spm=a2g0s.9042311.0.0.45164c4dzoBrJU . Anyway, they worked great until my Camry needed a jump, so when I jumped it from my 4runner, I guess the extra juice ran through the door lights and bridged some connections. After the 30 sec jump, the ECU was already fried. So thank you to everyone on here that helped out, you are quite wise, and helped save me a trip to the over priced mechanic!