LS430Jim

Hi ClubLexus

I have a 2005 LS 430 with the Premium Luxury package (Smart Access, ML Audio system)

The Rear Driver door was working as intended for several days after purchase. The smart access, courtesy light, power lock, and window from door or driver switch all functioned fine.

Yesterday I automatically Down the rear window. Shortly after I had gone to put it up but it did not respond.
I had attempted the rear window switch and no difference.

I then noticed the Smart Access was no longer functioning on this door, the courtesy light does not work either.

Just to note - the Door Open switch is functional (on the body of car) so the car indicates door is open. That is unrelated but may be useful information.

Interestingly, the 'lock' physical button on the handle still makes the car lock (except the affected door does not react)

I have checked the RR DOOR LH/ RH fuses (I read RH is the driver side?) and they are not blown.

I have removed the panel today but I am unsure where to check for power going into the door. I noticed no corrosion on any of the connections.

Can anyone help provide how I can determine if this is a door ECU issue, or an issue with the power to the door?

Update:

Techstream can communicate with rear door ECU and does not see any faults. I tried active testing functions for windows up and light etc but none work. The tests performed on the passenger rear door executed successfully.

I checked the White Black Line ground wire coming in to the ECU and it has 0.5 ohm resistance.

is there a way to get my window up??

Thanks everyone!! I look forward to anyone's advice.

BigBoomer

In the US the drivers door is LH (Left Hand) so you need to check fuse(s) for the Rear LH door.
The power for the LH rear door is the Red/Black wire (LH RR Door Fuse (20A)) and the power for the LH rear door ECU is the Red wire (MPX-IG Fuse (7.5A)).
The wiring diagrams in the Service Manual are a real PITA to read and I don't know where the connector between the door side and body side is located so the Red/Black may also be white and the Red may be Red/Blue depending on where you are checking.

If it's not a power issue then you will need to get a professional auto-electrician who knows CANBUS systems to take a look.

It may also be worthwhile disconnecting your battery for 15 mins to force all the ECUs to reset as I have heard of issues where an ECU gets it's panties in a bunch and the power-off reset fixes the issue.

LS430Jim

Hey bigboomer

thanks for your reply.

I dug a little further into this here’s what I’ve got.

I got the window up by connecting power to the Green and Red (thick) wire in the connector to the window motor. Thank goodness no rain.

I did try the battery reset for extended period of time. No change.

I’ve checked those 2 fuses - no issues there and they’ve got 12v.

I’ve got this documentation but it’s for Right door but I assume it should be the same
MPX module so this may apply.

I’m going to run through this to ensure the wiring is matching spec in the document.
I didn’t have the document when I was in there so I only checked one ground but it was in spec <1OHM

the only thing is I don’t have any DTC for ECU communication fault to rear door. Techstream communicates with it fine as well.

will report back soon. If anyone else has ideas feel free to throw it out there

given the door mpx is communicating to techstream but nothing is working, might be a module issue. But need to rule out wiring

thanks

Yamae

Your problem sounds like the failed driver portion of the rear door ECU.

The ECU has power transistors inside. Those transistors are used to drive motors supplying the DC current and also change the current direction. The drive portion can't be fully checked by the inspection procedure. I'd check the inside of the ECU using measuring equipments such as an oscilloscope and a DVM. This needs some skills and the quickest way to troubleshoot would be to replace the rear door ECU.

LS430Jim

Thanks for the info.

I have some electronics repair experience and I actually did remove the board from the casing.

lexus (toyota) did a very impressive job with the circuitry - all the solder was very well done and appears leaded. Additionally it seems they’ve applied a sealant to the entire board which may make testing points on it more difficult.


for what the time is worth - I’ve got a known good replacement coming for a good price.

I’ll have another update soon if that resolves the issue. Seems you would be on to something regarding the “driver” portion of the circuit has failed while the “brain” is still there however it is paralyzed.

Appreciate the insight - given what I’ve seen it appears replacement makes sense for cheap cost.

LS430Jim

It appears I made a mistake

when I was trouble shooting the radio issue I had I had accidentally replaced the rear door fuse with a 7.5 amp.

so it had blown

I missed the fuses in the top row behind the fuse door trim. So I had replaced it incorrectly.

thanks guys for the help. Looks like I won’t need that extra computer