I have been trying to figure out an electrical problem for a few months now. Initially, My battery was being drained nightly as if something was running after the car was off. I did a diagnostic and there was an ECU code. So, I replaced that fuse. That worked for a little while. Since then I figured out the alternator was bad and battery, so both were replaced. I also replaced the ECU. Though I have also done the ECU reset, today, my fob does not work nor do any of the electrical components (power door locks, power door opener, garage door opener) in the vehicle without the key in the "on' position. I did find a fob reset video but I can't reset the fob because it requires cycling through the power door locks to reset (which don't work when the key is not at "on") . Also, everything resets (clock, seat memory, etc) when the car is turned off. Any ideas would be great. Thanks in advance.

 

Here is what I have done chasing this issue: Battery, alternator, starter relay, door control receiver, ECU, and Toyota dealer diagnostic (they replaced a bulb a couple of fuses and told me I needed a new ECU...newsflash, been there done that). They also told me I needed a Lexus specialist. No sign of corrosion in the cabin though I did have a moisture problem in the floorboards that I rectified. So, all accessories in the cabin work in the ON position. Even the headlight courtesy exit delay works when leaving. In the ACC position, only the clock comes on (however, it resets to 1:00 every time). Fuse? Relay? SMH.

 

That’s a tricky one. Have you inspected all the wires connected to the ecu for corrosion or wear/shorts?
Maybe try replacing the main 100 amp fuse?
I would try to find someone who specializes in car electronics and ask them a few questions to see if they’ve ever dealt with a similar issue.
otherwise this is going to require a multimeter and a lot of patience/ disassembly.
I don’t know where I would even start. Especially after replacing the battery alternator and ecu. I would think there is something amiss with the wiring. Maybe some plastic wire coating melted somewhere and you have a short. Wiring is finicky and more and more so as wiring complexity increases.
good luck though.

 

Hi ddking, I'm glad your last thread got moved here because I am struggling to find the context of your issues.
You make the distinction between key "on" and key in "Acc".

Can I plz ask.

1: With key turned to "ON", what is the car doing properly and what is it not doing properly?
2: With key turned to "ACC", what is the car doing properly and what is it not doing properly.?
3: When the car is running, what is the car doing properly and what is it not doing properly?
4: With no keys in the igntion, what is the car doing properly and what is it not doing properly?

One last question, does the car run and driver properly.

 

Hi ddking, I'm glad your last thread got moved here because I am struggling to find the context of your issues.
You make the distinction between key "on" and key in "Acc".

Can I plz ask.

1: With key turned to "ON", what is the car doing properly and what is it not doing properly? - Clock, dome, radio, hazards, entry lights work. Power door, door locks, windows do not.
2: With key turned to "ACC", what is the car doing properly and what is it not doing properly.? - Everything works
3: When the car is running, what is the car doing properly and what is it not doing properly? - Everything works
4: With no keys in the igntion, what is the car doing properly and what is it not doing properly? - Headlight delay and floor lights work. . Fob, locks, seat adjustment, seat memory

One last question, does the car run and driver properly. - Yes, the car is actually running perfectly.
I did come across a description on a Lexus parts in Plano website that said this: Body Control Module - Repair or Replace
A failed body control module can have many symptoms, including intermittent operation of power windows, locks, and seats, a malfunctioning alarm or keyless entry system, or warning lights on the dashboard. Have a technician diagnose your Lexus RX 350 with a Lexus approved diagnostic computer.

 

All of the body interior electric and features run thru the Body Ecu.
I have a spare unit I bought on fleabay dirt cheap because it's nice to have a spare for quick testing verses chasing wires and harness junctions that require tearing the interior apart to get to them. lol

The Body Ecu can fail in numerous ways and cause all kinds of complicated issues so it can always be suspect but when reviewing the complexity of the wiring for our cars it's not always so simple.
Also, the Body Ecu seems to have "modes" of operation based on my testing with the system and depending on the "mode" allows the Body Ecu to allow or disallow different features on the car.

In my understanding, the "mode" depends on the power signal sources that show up at the Body Ecu and the Body Ecu has many power sources(see below).

Since your "ACC mode" is working correctly we can rule that one out.
Since your "Running mode" is working we can rule that one out.

Seems to be when no keys in the ignition or when key is "on" you have lost features.
It's possible to have a bad Body Ecu or it could be a bad wire harness junction.

Test - does the passenger side door lock work when no keys in ignition.?
Test - does the passenger side door lock work when key is switched to "ON"?

Pic below is for power distribution:
Rule out ECU-ACC fuse(ACC mode).
Rule out ECI-IG2 fuse(key on) only if wipers work when key is on, if they don't work when key is on you have a bad Body Ecu(most likely) or damaged/corroded harness junction(likely).

Not ruled out yet: Door 1 and Door 2 fuse shown below must have a power signal to the Body Ecu for "keys off" mode in my understanding, there should be power thru these fuses.

(posted in fair use for commentary and discussion)



PS- based on your symptoms compared to the Body Ecu "modes of operation" and finding an intersection in the schematics for the symptoms reported, I suspect you have a bad Body Ecu. More tests would have to be done but I highly suspect it has failed or damaged connector that plugs into the Body Ecu(less likely).

PS- if it was my car I would pull the driver door module and test all the "modes" again and see if the driver passenger door lock works on the passenger side. Driver door module is easy to remove and unplug and is built into the driver door window switches. This will rule ot a bad driver door module causing all the problems due to throwing garbage data down the multiplex data lines depending on the mode however it's still most likely you have a bad Body Ecu, just throwing a hail mary hopefull fix for you.

 

Very insightful. I appreciate you. Great thanks!

 

Just because you put in new parts, that does not mean that it is good. Put the old ECU back in and see if things will work with the key off.

 

OK. Passenger door doesn't lock with no key or ACC but does in ON. I haven't found any corrosion or any wires lose. The way this started happening leads me to believe that you are on to something...just one feature after another stopped working. I will find my fuse diagram and go through those fuses too. Where is the door module located? Also, I haven't checked the multi-plex network door computer and it appears from the diagram that it is located on the pillar behind the front passenger seat, is that correct? There was a moisture (sunroof leak) that I fixed and that could be causing problems due to moisture/corrosion there too I suspect.
I went through the additonal suggestions and its all pointing to the Body ECU. Where is the Body ECU located? Also, I tried to find it on Ebay and couldnt find anything but the engin ECU. Do you have a part number?

 

Hi ddking5, sorry for the late reply I have been working around the clock and haven't had the time to dig thru the schematics.
I can see why you have struggled with this for months because your symptoms keep getting more interesting.

To buy a "Body Ecu" for dirt cheap on fleabay do a search for "fuse box" since most sellers don't know that the Body Ecu is located inside it.
To get the part# you need and to buy the right fuse box(body ecu) you will need to know what you are looking for because our cars have more than one fuse box.

By taking the plastic covers loose under the steering wheel and lay on your back in an awkward position and shine a flashlight up in there and see the part# you need(not sure if part# is different for cars with different years and features or if they are all the same) and compare to fleabay pics.

Body Ecu is located under the steering wheel behind the plastic approx where your knees are are while driving.
Always a good idea to unhook the battery first, there is airbag stuff under the dash.

Add- I bought two on fleabay, one to keep for a spare as a "tester unit" and as you can see how valuable it can be just to have it for that alone, and another I bought just to tear down and reverse engineer it.
Other members have replaced it but I haven't so I have no tips and tricks to offer on installation, my spare sits in a tote in the shed. lol

Also, each door has a door module and there are other modules onthe car.
On the driver side the module and widow switches are all built as one unit.

Each door module communicates with the Body Ecu in a Master-Slave relationship where the Body Ecu is the Master and all the modules on the car are Slaves, best I understand it so far.
In this Master-Slave relationship, the door modules cannot communicate with eachother aka the master door lock on the driver side does not unlock the other doors- rather it sends a telegram(or equivallent) of data to the Body Ecu and the Body Ecu acting as a Master decides to allow or disallow. If allowing a feature- it sends a telegram of data to the needed module down the mulit-plex data line and only the module it's adressed to will follow the command.

Basically how it works- the Body Ecu manages the body's interior electric.
Inside Outside that Body Ecu are fuses and inside are many junctions where several wire harnesses plug into it both on the outside and inside.

Me and another member did a tear down of it and posted up pics.
Here is my teardown. Link https://www.clublexus.com/forums/rx-...with-pics.html

Add- for anyone following along, if you look under the dash on the driver's side and find the fuse box- you are looking at the bottom edge of the Body Ecu/fuse box
"ALL-IN-1" unit!

 

Hello,

Thank you for your detailed description. I have an interesting problem: ONLY my passenger door will not unlock via remote or driver's switch panel.
The passenger door lock tab will physically unlock and and lock the door, but must be manually moved.

When I attempt to unlock all doors via remote or the driver's switch panel, the passenger door will not unlock. I am able to roll all windows down in the vehicle from the driver's switch panel.

I am leaning toward a burnt out passenger door actuator motor rather than body ECU.

What are your thoughts?

 

There are other possibilities besides the solenoid. First of all, when unlocking the door electrically (i.e., key fob or the switch in the window switch panel), do you hear the solenoid make a click or thunk sound? if not, then maybe it is the solenoid. If there is a sound, then maybe a connecting link from the solenoid has fallen off.

To look inside the door, you will need to remove the door trim panel. Here is a video that will show you how. The video is titled "speaker removal" but that job also requires the door panel to be removed.

 

Thank you for the response and the link. I do hear a sound, but the lock does not activate. I'll take a look at the connecting link this evening.

When I physically lock the passenger door and then use the lock button on the key-fob, the vehicle will flash a confirmation "locked" with turn signals.
If I have the passenger door unlocked, and I press lock on the key fob, all other doors will lock, and no confirmation will flash.