Electrical issue...Key on/off...Dome Light/Door Locks stop working

I've got a 2010 4Runner that developed this issue in 2019. I stopped driving it last year because I've got other vehicles to drive and it may need a new battery just from sitting. It was new in 2018.

The symptom is that everything appears to work normally when the key is switched to the on position. When you turn the key off, about 10-15 seconds later, the dome light turns off abruptly and the door locks stop working (which was first noticed because that 10-15 seconds allows you to lock the doors using the key fob, but you then have to use the key to unlock them). My understanding is that the ECU sends ground to those circuits, but the few wiring diagrams I've found are tough for me to read and compare to real world.

The normal on/off of the dome light switch turns the light on and off because it's coming from a third wire. It's the automatic courtesy light circuit that's dead.

Additionally, I've seen the door ajar lights come on and act up while the doors are closed. This can be witnessed through the windows, but I went around and tested them and can't seem to find any issues there, so I'm wondering if this is a wiring issue or something else. I've visually checked and pushed on the ECU connections, but not gone beyond that. I'm reluctant to start pulling things apart because I can't see any visible evidence of damage and big hands make the job not fun.

Could this be more simply a relay somewhere? I've checked all of the fuses inside and out, but not sure about the relays or other things to check. I've removed the short pin a number of times to see if that had any effect on the ECU, but no luck there.

 

Do you have a good battery you can swap with? That would be the simple thing i would start with.

 

This battery holds a charge well enough to test. I have charged it up and it reads just over 12 volts.

 

@SlvrSlug is right. First thing is to troubleshoot with a known good battery.

What this sounds like to me is a failing/and or failed main body MPX ECU which controls all the door lock relays inside the cabin fuse box and the dome relay under the hood. The reason I say this is all the door ajar switches, and grounds for the door ajar courtesy lights go to that main body ECU (thin black plastic with 3X white connectors), so if the door ajar lights are randomly turning on with the doors closed, that says the ECU is likely no good.

I would pull the cabin fuse box and pull the main body MPX ECU out of it and visually inspect it. There is a 30 pin connector that connects the fuse box and MPX in addition to the 3X connectors on the side. I would also pull the black plastic cover off the ECU PCB (clamshell cover held together by latches) and inspect that for signs of shorting and or damage. It's easy enough to remove the 3x bolts holding the fuse box into the dash, and the larger connectors on the front of the cabin fuse box are the lever style. Push down on the tab and pull the black plastic lever towards you.

Let us know what you find.

 

Thank you. Honestly, I'm pretty good with doing these kinds of things in most cases, but not thrilled about working upside down in tight spaces on a 4Runner that actually runs... I've been reluctant to get in there and mess with it because I know the ECU prices are $500ish and was hoping the problem would be a $5-20 relay or something that I could see standing up. Your detailed instructions give me a little more confidence. I've already got part of the door and dashboard pulled apart to visually inspect things. I just stopped short because of lack of time.

This whole thing started right after the sunroof leaked water during a heavy rain...which was about a month after my wife paid someone to detail the 4Runner as a birthday present. I figured the detailing dislodged something and plugged the drains on the sunroof....but wasn't sure if they sprayed cleaner somewhere that shorted out something either. The water leaked more on the passenger side, so I'm not sure how it could have affected that circuit unless it somehow reached the dome housing behind the sunroof...which I don't recall seeing. That all could just be a coincidence, but I'm a cause and effect belief kind of guy. Things don't just break. They break for a specific reason.

I'll inspect the ECU when I get some time to work on it and report back. Do you know of anyone being able to fix ECU's without replacing them? I'll have to see if the board is toast, but interested if anyone's tried swapping capcitors/resistors and the like to get them operational again.

 

By just over 12V like 12.1 or higher?

I'm with getting a good battery or throwing it on a charger.

 

Agreed, things do break for a specific reason. It could be from the water, but it depends where and how much dripped onto a specific area.

In regards to fixing the ECU, its easier to replace the entire ECU vs trying to fix it. If you look at the board it is all very small SMD components. To do it correctly, you would need a very expensive hot air rework station and be able to figure out the cap values when they are not marked. I've messed around with these MPX ECUs and from the damage I have seen on some I have experimented with and other issues people have had, there are usually burned traces in addition to burned components. Look on ebay to see if you can pick a MPX up used. You are correct in that new they are about $500, but used you should be able to pick one up for around $100.

Any 4Runner specific MPX will pop right in and not need programming for it to work. Only thing to keep in mind is the MPX has to come from a 4Runner with an ignition equivalent to what your 4R has, i.e. if you have a conventional ignition vehicle requries and MPX from a vehicle with conventional ignition, not a push to start vehicle (there is a programming difference based upon smart key vs normal key).

 

A fully charged lead acid battery should be at least 12.8 volts when not charging - and over 14 when charging.

Based on what you are reporting, I don't think the battery is related necessarily.

 

Guys, batteries displaying 12+ volts does not tell the whole story - the proof is in the load capacity of the battery and the easiest way to check that is acquire a load tester (borrow or get one from any tool outlet - they run about $30 or less - then you got another useful tool in your collection). The load tester (cheap ones) typically apply a 100 amp load to the battery, then you monitor the voltage drop on the tester's meter. Typically you apply the load for about 15 seconds (it just a single toggle switch on the tester - very simple) - the voltage should not drop beyond 10.5 volts - if it does and it quickly continues to drop within the 15 second timeframe your battery is toast. If voltage holds steady above 11 volts then your battery is likely okay.

As others have stated, the first step in diagnosis is to ensure your battery is rock solid.

 

I removed the MPX and can see obvious trauma to the board. There was an oily burned residue under the connector. I used some alcohol to remove it and can't see any visible damage to the paths. Using cotton, alcohol, and a dentistry tool I cleaned up the board and it doesn't appear to have overheated.

Flipping the board over, it appears to have originated between e32 and somewhere else. The bottom side of the board is clean with no signs of problems. The board has some kind of coating on it and maybe moisture cause a short under the connector that then affected the coating, but not enough to blow any fuses?

Should I put a multimeter on it and test anything specific or just pop it back in and see if it works now that it's cleaned up?

 

After cleaning...

 

You're venturing into territory unknown to me - good luck.

 

Hmm... that's interesting. Oily burned residue but no physical damage to the board or paths. Was the corresponding connector on the fuse box discolored? Does the fuse box itself smell burned at that 32 pin header connector? Post up some pictures of the fuse box please if you can.

Pin #32 on the MPX board connector is ignition power from the IG1 NO. 1 Relay (internal to the cabin fuse box) and is fused by the 10A ECU-IG NO.2 fuse. Double check that fuse just in case.

The coating you are finding on the MPX circuit board is called a "Conformal Coating" that actually protects the circuit board and its components from environmental conditions, such as moisture in the air, etc. They are usually a plastic polymer of some kind. Nothing to worry about, and I wouldn't try to remove it if at all possible. If a liquid caused a short it would blow the corresponding fuse before damage occurred.

 

My cell phone camera isn't great, but all of the residue cleaned up. The inside of the connectors didn't have any visible damage, but I didn't look on the back side of the fuse box. It didn't have that burned electronics smell, but I can't see well enough under the connector to really know what that side of the board looks like. I would have to desolder all 32 pins and I guess what you would call the rivets. I ordered a used MPX already today just because the darkening makes me think we're at the scene of the crime...but if I can fix it without using the part, that's great.

In troubleshooting, I pulled and tested all of the fuses twice...inside the cabin and in the engine compartment. I found nothing out of the ordinary. I checked the ECU that lives in the liftgate and didn't see any signs of wear on the wires, but didn't inspect that board.

I'll definitely check those fuses again tomorrow. I didn't mess with the relays. I wouldn't know which one to pull.

Thanks for all your help.

 

I put the ignition fuses on the meter and they're all good. They didn't have any visible signs of being blown, but I still test them.

I pulled the cover off from the box and can see the relays.... finally. I was trying to figure out where they all lived. Do you happen to know which relays might control the ground signal circuit when the key is in the off position? When I power off the vehicle, I have about 10 seconds that everything still works, so I think when the key goes off, the circuit flips to a further reduced load to make sure nothing else is powered and the ground signal is enabled by that relay.

I'm not sure how to test a relay, but I may just figure this out.

 

Good, that eliminates the fuses. I'm no electrical guru as there is a lot I don't know/fully understand, but If the relays don't look like they have any visible signs of damage I think they are probably fine. I don't remember specifically which relay is which on the fuse box PCB. I attached two pictures showing the soldered pins for all the relays on the back of the board. Orange is the smaller relays (door lock control relays), purple the larger relays (Ignition, ACC, Fog, Backup), light blue is the resistors across the relay coils. Visually inspect, but again I would be surprised if there was damage.






Also, looking at the long 32 pin PCB header, I don't see any signs of heat damage caused by a short/greater current load. If something shorted there would be evidence. Pin #32 is Igntion power on the PBC header. Pin #11 is the pin the MPX grounds to effectively close the relay contacts and "turn on" the ignition relays NO. 1, 2, 3, 5, and the ACC relay so power goes to the fuses for each system in the vehicle (there is no IG NO. 4 relay).







I am leaning towards this being a bad main body MPX. The MPX grounds the relay control circuits when the key is in the "ON" position. I think a replacement will probably solve the issue.

 

Thanks for the schematics. I'll hopefully have some boards to try out soon and a used MPX. I still would like to fix this one if it's something simple, so I may keep this on my bench and try to figure out what's blown on it before putting my 4Runner back together.

 

yeah no problem. Let me know if you need anymore. Doesn't hurt to mess around with a part that is already technically "broken". May as well experiment with it. Keep us posted if the replacement MPX solves the issue.

 

I think I may have some more pin out descriptions on the actual problem I'm experiencing (based on my troubleshooting). I printed out a paper that had one page talking about the connectors and which pins where which... I didn't understand the pin numbers or codes because I hadn't pulled the boards out and wasn't 100% on fixing the issue myself, but your diagrams mixed with seeing the board help me understand a little better on how they coded it. I may be able to figure out just where to look. The MPX could definitely be the issue since that's where the residue was and if it's not sending the correct voltage to the relays, they won't work.

I'm also wondering though if one of the relays is an NC (normally closed) relay for when the MPX signals the power is on and pulls the 4Runner out of "Off" or low-battery power consumption mode. If I can find those papers, I may dig in and then see if there is such a relay that may just be dead that controls Off-state power to the courtesy, dome, and actuators (plus key remote unlock receiver). I have this picture of how it all works in my head, but you never know whether or not it was an MIT guy that designed it or someone with some sense. =P

 

The replacement MPX appears to have fixed the problem. Thanks for all your guidance. They used MPX was $150, so I'm going to call this a win if it doesn't start acting up again.

 

Good to hear the problem is solved. Funny enough, this is the 4th MPX failure I have seen over the last year. Makes me wonder sometimes.

 

The stuff I've read about other people's problems usually has to do with them making modifications to courtesy lights. (Chinese led power supplies) I don't get it. I want incandescent lights and AM radio.

In my case, my failure happened shortly after my wife had my 4Rinner detailed. Debris clogged the sunroof drains and not only was I dealing with bad locks/lights, but a mildew smell. I wouldn't be surprised if water had leaked somewhere during those events and caused the failure. (It wasn't immediate... All that happened within a month though). Who knows what the guy that detailed the truck did? He could have sprayed water or cleaner anywhere on the door sensors or other inputs that feed the MPX and sent 12 volts to it instead of ground. It was an 8-year-old vehicle at the time of failure, so it could just be age too.

 

Hello all, hoping I can revive the thread and get some help. I have all of the same symptoms. Everything works fine until I turn my car off... then about 10-15 seconds later all the dome/side door lights go off and the key locks stop working. Turn the car into on position and it all works fine again. I also has this happen after a strong rain storm and it seemed to have some water on the driver side floor. I had a brown area showing damage at the exact same spot. Funny how those Toyota engineers were so good that they can get leaking water to drop in exactly the same spot. Question is how can I find a replacement part... the part # is 89221-35112 but I can't find that part anywhere. There are plenty of similar looking parts but all with different part numbers and for different car models and such... just don't want to spend a lot of money and time to try to swap it out for the wrong part.

Thanks, Bill

Has anyone been able to actually repair their board for the specific damage?

 

I sit in mine last night after getting home and because I didn't open door it knew I was in the seat and it kept rebooting the light until I got out. They didn't get my hatch shut completely and I didn't have a hatch light or it was enough to keep it off and dash lights started blinking, Traction control and something else and that was only thing I had done . I assumed to get my attention so nothing fell out back. Instead of dealer take negative cable off and flash a reset after you make sure everything. I think Toyota is going away from adaptive cruise and going to sell you an illegal than and you have super cruise while you sleep. Hehehe. Sorry it's just ridiculous.

 

I believe the door opening and closing is longer. Limited is smarter than me and has auto settings. Just point and steer mindlessly. I thought about using running boards for rock rails once, but I love mud. I drive around rocks. I don't want to modify to much or I won't like like I did and you don't get the same dependability if you go to crazy. 4wd system is so good you get need tires, friend and two strap. I would put my Ramcharger in 4wd and the solenoid stuck and I didn't know until I needed. I'm thinking about building plywood and fiberglass skid to seal up the spare mud cup. As long as you can keep moving you can usually bounce it across them. I don't see pay hundreds for a shiny skid plate bounce rocks off of. I found a metal oil filter house on mine and filter was an inch shorter, plus same type metals can bind and seize. It's plastic for some reason. It reduces oil heat from housing and two different materials that don't bind . That being said, don't torque the housing. Once it stops turning stop. O rings seal better because there's more pressure on a smaller point. I got my housing from eBay for $60 in Lexus Toyota boxonce I knew it wasn't Chinese made. It appears correct. Came from Michigan and it has Keno on the side but it appears correct, filter fit. Why do people do that? If I tote that off then I am screwed anyway because the engine pump your oil out in an amazing short amount of time. If your oil filter gets ripped off. I understand why oil change guys do it to increase speed it and leave. I have come out the woods bolts of skid . I will try to post a link from Facebook. I don't like laquer painting. I tried and it's alwfull. You have to apply multiple coats after each dries. Easy maintenance, but I thought about camo wrap. I tried different bug shields and the AVS 1 was better than model II or weathertech if don't want to clean bugs your luxury 4 refrigerator. For me.

 

Hi Bill,

Welcome to the forum. First, sorry to hear you are having this issue. What model year and trim is your 4Runner? (this is important so that we as a group can help you) Before you go about fixing it, you might want to clean out your sunroof drain lines if you have a sunroof, or find where the water is coming in at. Also, what's the condition of your cabin fuse box?

In regards to fixing your Main body MPX ECU, the bad news is that it is toast. These are not fixable when they short out. You will need to find a replacement, and I advise looking for a used one. You can use any 4Runner Main Body MPX from 2010-19, so long as it A) matches your ignition type i.e. conventional vs push to start (If it comes out of a limited, it won't work) and B) if you have crawl control you will want one out of a Trail/TRD trim. Part numbers won't be helpful to differentiate ECUs as most either end in -230 or -240. It seems Toyota differentiates the part by the software coding number and not the physical hardware number.

 

Hello Old Red, I have confirmed sunroof drains are cleaned out and free. Cabin fuse box is fine, no fuses are dead anywhere. I have a 2013 Trail edition.... Any idea where to find the correct MPX main body replacement part

 

Do different year 5th gens all have same plug .

 

I would look on eBay, LKQ online for a used one. Make sure it is coming out of a TRAIL/TRD edition 4Runner, not an SR5 or Limited. SR5 Trim will have a blue sticker on it and end in -230 for the 2014-19MY. TRAIL/TRD/Limited will have a gold sticker for the 2014-19MY and will end in -240. You need to run the vin from the donor vehicle to confirm it is not coming out of a limited.

I would recommend calling your local dealer and asking them to get you the correct part number as I don't know it off the top of my head.

Yes, all 2010-19MY 4Runners are wired with the same plugs for the MPX main body ECU.

 

Okay so the only one I could find was out of a TRD, with number 89221-35240 with a yellow tag. I have a Trail edition but mine is 2013 and my part number is 89221-35112.... any idea if this one works. All the online descriptions start show 2014-2019, but I can't find specifics about 2013....??? not sure if this one will work?