07toyota

Greetings from Spokane, WA!
1999, 140K, purchased at 113K four years ago with impeccable maintenance records.

Disclaimer: in attempting to replace the driver's door lock actuator motor, I made things worse. I put strain on some wiring.

Search results are plentiful but I would like to list these symptoms together in hopes that someone else may have an idea to follow. All symptoms are new since my "work" above:
- Driver's window stuck in up position - master key in driver's door lock DOES open other three windows and sunroof;
- Driver's door courtesy light not functioning (bulb checks out);
- Trunk release button not functioning (valet button unlocked), nor does the key fob button;
- Driver's door master switch, including auto up/down, for other three windows DOES function, as does the master lock button.

Visited the local Lexus dealership, they recommend replacing motors for driver's window/trunk release. I disagree. No charge.
Following the visit, two new symptoms appeared:
- Headlights do not turn off automatically after ~30 seconds, whether "ON" or "AUTO";
- When sunroof is open, warning indicator NO LONGER flashes when car is turned off.

I checked all blade fuses, good.

Does anyone know if there is a computer/multiplex that impacts these areas as a whole?

Any feedback or ideas are appreciated. I also own a 1997 LX450, and the online support for these vehicles boggles my mind!

Banshee365

You've seen the door ECU when you had the door panel off. That ECU multiplex's with the body ECU mounted up on the firewall up and to the left of your brake pedal. How hard are we talking on stretching wires here? Any chafing? If I were you I would remove the door panel, unplug the window regulator wires (2-pin connector), and test the motor by hot wiring 12v to the terminals. Don't let them short of course. Window motor direction is reversed by reversing polarity so if you fail the first time switch terminals and try again. I bet your regular motor is fine but you won't know until you troubleshoot that this way.

Yamae

Driver's window, Driver's door courtesy light and Driver's door master switch are all controlled by the MPX Door Computer for the driver's door. Trunk release, Lights and Sunroof are controlled by the MPX Body Computer. Those computers are connected by a communication bus line called BEAN and the communication may be not working right or those computers are not working right, judging from your symptoms.

I'd start to check the bus line first. Without analysing your car myself, I can't say enough but my assumption is as follows. When you put strain on some wiring, you damaged the bus line and the BEAN bus communication system began to fail.

07toyota

Thank you for the quick replies, much appreciated.
Banshee, I will test the motor as you indicated but feel fairly sure that the window motor, as well as that in the trunk, are fine.
Yamae, thank you for the information. I do not own a FSM, nor do I have wiring diagrams, nor am I an electrician - if you have time, can you tell me more about this bus line?
In response to both, I remembered that with the door panel off, I plugged in the door handle and the alarm triggered. Key in ignition turned it off, but I wonder if these symptoms could ultimately be related to the theft deterrent ecu???
Also, the wires stressed are located at the rear of the door - I removed the door lock actuator without removing the window, so there was some creative and none-too-gentle contortioning done.

Yamae

I'd quickly check the lines to pin 9 and 18 of the connector C used at a black box which is the MPX door computer built in the door. Those two pins are the BEAN bus lines. The bus signal goes into pin9 and goes out from pin18. I'd simply use an oscilloscope to confirm the signal but a simple continuity check using a circuit tester may be useful to find the damaged part. Depending on the damage, you even can find it by your eyes.

YODAONE

This may not seem obcious, but have you any water leaks.

There are numerous connectors on passenger side right of footwell that if doused will cause issues described....

The likely culprit is the sunroof drains are overwhelmed and water leaks across headliner and down windshield support and onto these multplex connectors.

Jsiliga45

Hi Yamae,

So i have a 1998 Lexus Ls400 and had a short in the courtesy light which has caused me to lose power to my driver door lock,window,mirror,and trunk release but everything else is working. I replaced the mpx in the door, and the mpx body with battery disconnected and still nothing. Any ideas of what it could be?

Yamae

Have you checked fuses "10A MPX-B" and "10A Dome" located in the fuse/relay box behind the battery? You also need to check the fuse "15A Power IG" located under the dash. These fuses are related to the MPX body computer.

knosalaa

Hello Yamae, I have 94 ls400 8/94 build and having issue with trunk release lever in the cabin. No issue with the lock, it is unlocked, fuel door release works fine. I can hear relay click but very quiet. Could you please direct me where I should look? No electrical issues accept for this one.
thank you!

Yamae

Sounds like the actuator is not working.

DroLs400

Have u checked ur fuses a lot of people go straight to assuming it’s the motor or water damage or any damage to the wiring, changed all my regular small fuses in fuse box in engine bay and fixed all my windows and issues

knosalaa

Where is the actuator located?

Yamae

It is located in the Luggage Compartment Door Lock Assembly.