DGMD

Hi all- i have a 2000 ls400 which i recently replaced a front driver power window motor and regulator (cardone remanufactured) and rear driver door lock actuator (aisin rockauto) simultaneously. Car now has a parastic draw from mpx b fuse diagnosed by a shop by multimeter testing. With the fuse unplugged, the keyless entry does not work. The car will start w out fuse and both the window and actuator work when car is running. Any ideas to pinpoint what cld be causing the draw (or any other source) besides pulling both door panels off again?

Yamae

Did you disconnect the battery when you did the job?

* If yes, you now need to check which line is drawing the current. There are 15 lines after that fuse such as MPX body/door computers, power window, power seat, wiper, washer and etc. The first step might be to try to remove the connector of the re-manufactured regulator or the door lock actuators because those are the only parts replaced. These days, some re-manufactured units are not quite reliable, I feel.

* If not, I worry about either the MPX body or the MPX door computer is partially damaged. The communication bus line of them is often damaged when the replacement job is done without disconnecting the battery. It is always important to disconnect it when you do jobs related to electric/electronic units because the car has the communication bus called BEAN and it is always working even the ignition key is removed. I have seen many DIYers and even mechanics failed the job doing electrical jobs.

DGMD

Thank you Yamae... have read your other posts and advice is always helpful. I hope it is not damage to the MPX body or door computers... That would be a real problem. I was not present when the work was done. Are there any other symptoms of MPX body or MPX door computer damage? Everything else works with the fuse out, when the car has started and is running.

Also, have you run into the problem of a solar control sensor (automatic headlamps) not working? I have replaced all fuses in my car, and tested out a used different solar control lamp sensor, to no avail.

Yamae

The solar sensor sends the signal to the MPX body computer and it drives the head lights relay. Other than that, the MPX body computer is related to following issues as far as I know.
* Key-less remote entry
* Doors (Lock/Unlock, Window up/down)
* Door mirrors
* Dome lights
* Air bags
* Trunk solenoid
* Moon roof
* Seat belts
* Alarm

I think I know Clesiors/LS400s slightly better than the average. I live very close to the Toyota Head Quarter and I used to had some connections with it. There are some people whom I know there a lot. I own a 98 Celsior and I make it a rule to maintain it myself and share what I know and experienced to those who love Celsors and LS400s. Due to my past job assignments in abroad, I barely speak some foreign languages and my intention is to keep Clesiors/LS400s on the road world wide as many/much as possible. That is way I still am here and post. This post will be my 1900th post. They say that I can make some big money but I am not interested in it. I think I can buy a latest LS but I am only interested in my old 98 Celsior. I love it very much. May be the same level or close with my wife.

DGMD

So pulling the door lock actuator and power window motor and putting old ones back in did not resolve the electrical draw. Looks like MPX door computer is probably damaged. Should I replace just that one first, or body computer as well? TY.

DGMD

The draw turned out to be coming from the steering telescopic motor which is functioning. Shop left the motor unplugged and battery does not drain on its own anymore. Looks like a few threads on this, anyone done this repair? Shop is quoting me $641 to replace...kind of pricey for a 18 year old car, may just leave alone...

Yamae

Do you have any other problem related to the bus line?
If not, the problem may be caused by the motor driver circuit which is in the Tilt and Telescopic Computer unit.
If yes, the bus line may not be working fully right.

DGMD

No other problems related to bus line. So replacing the telescopic motor may not take care of the issue?? How do I repair that motor driver circuit/tilt and telescopic computer unit...

DGMD

Nothing else on bus line looks like its not working except for auto headlamps which have not worked since I owned the car, and prior to the draw. I'm not sure how this problem came although I did have the instrument cluster swapped for dim needles... maybe this caused the issue. Thank you Yamae, I will try to replace the computer unit and report back.

Yamae

There are some other items to confirm if you are interested in. The telescopic motor has a position sensor and depending on the signal from it, there is a possibility that the motor driver may continuously send the current to the motor.

I also must inform you that the seat belt hight adjusting motor is controlled by the Tilt and Telescopic Computer too. Those 3 motors for Tilt, Telescopic and Seat belt hight have a position sensor each and all of these 6 are connected to the computer. It may be an idea to check those before replacing the computer unconditionally.

I often am called by local shop owners and dealer managers and I find them not skilled enough to fix computer related problems. They simply replace units and notice that the problem is not fixed. Then they replace related parts next to next and finally they give up and call me. I use an oscilloscope, a spectrum analyser, a logic analyser, an ESR meter and other equipments to find the exact root cause of the problem. So far every problem I was requested to fix was successfully fixed. One of those is the QAS capacitors problem in the ECU. I am not doing those for money but just for my curiosity. Thanks to the American Government sending me enough pension for me to live the rest of my life.

DGMD

Have not replaced the computer or telescopic motor yet. I did notice with the telescopic motor disconnected and the draw gone, the tilt motor works but the drivers, seatbelt motor and tilt motor do not function. Does this give any more information?

PinnySkenis

Did you ever get this sorted out? I have a large draw coming from the same fuse so I’m curious if this could also be my problem.