Just took possession of a 2012 RX350 fwd w 82k miles.

These electronics work only half the time and can't determine why or when. It's all of these at the same time either will work or won't work:

Driver's memory seats button on drivers side door (but the power controls on the seat do work)
Rear view mirrors controls for driver and passenger mirrors.
Power tailgate (regardless of interior button, key fob button, or handle on the tailgate - none work). When those controls work, the tailgate works properly.
The power steering and power seat automatic movement to driving position once seat belt is inserted into buckle. Sometimes it does put me into my driving position as it should and then when I stop driving and turn off the vehicle and unbuckle the seat belt, the seat and steering wheel won't move back to give space for egress.
When putting car in reverse, the rear view mirrors will lower correctly and return to normal driving setting (sometimes won't work at all.)

The above 5 items will all work correctly or none will work. It's never 2 of 5 or 3 of 5 and etc. It's 5 of 5 of 0 of 5.

These will sometimes start working (all 5) after driving 15 minutes when it didn't work at start up.
and they will work at start up and not work at the end of the drive.

Is this a sign of a weakened battery? A bad module of some sort? Does a reset of something else need to be done (I did disconnect the battery for an hour but it didn't help).

Is there something like a multi-use fuse that controls all these areas at the same time (I'm not a mechanic...pardon my terminology usage).

THANKS for any suggestions. (I was quoted $600 by the Lexus dealership to perform a diagnosis...of course would prefer a DIY fix if possible.)

 

Could be a grounding issue. First thing I would do would be to read the OBDII codes.

 

Thanks. I will dust off the multimeter as a first step and do visual inspection for wiring issues coming from negative terminal. I don't have a full code reader but I do a CARID code reader and will see what code, if any, pops up.

Any idea what code would come up for a grounding issue?

 

I agree with the above recommendations. First see if CarId finds any codes. Then proceed with further diagnosis.

Where did you find this vehicle? Do you have a CarFAX report? Who sold it? What is their warranty, if any? Accident history?
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You can go to the Lexus drivers site linked below, join for free and enter the VIN of any Lexus you are considering to buy used and then it lets you see the dealer service history and the car build sheet that shows its options. The site is a bit cranky and does not always work, so you may have to try a couple of times. https://www.lexus.com/My-Lexus/account/create-account

​​​​​​To see the service history at Lexus Drivers do the following:
On the page that lists the car whose VIN you entered there will be a line that states
Vehicle Health Report
Learn More - click this box
Then on the next page it will state
My Service
On the right side it will state Service History
View History - click this box to see the service history
Then it will slowly take you to a page you need to scroll down to see the service history
Each entry will be a line, click on the + at the side to see more about each entry

 

my 2cents:

Please examine the fuse box and the A pillar channel on the driver side. Look for evidence of water intrusion ... corrosion/discoloration of terminals. This i s for the draining water, and there is also the question of rising water. There are quite a few flooded vehicles [declared and undeclared] in the country.

Saliim

 

Sorry you might have brought a lemon. It is very unusual or unheard of for the RX to have electrical gremlins. But yes, start with the suggestions above.

 

The sunroof drain holes were clogged and I just cleared them. Water had collected after a rain and then I cleared the drain holes. I checked the fuse box...no sign of water intrusion now or in past.

 

The car was bequeathed to me after the death of a parent. Maintained well from what I understand. Not flooded.

 

codes from CarMD device:
C1241 (looks like a battery or alternator - Autozone had said they're both tested as "good")
C1406 (short in front left speed or ABS sensor)

Multi-meter: engine off 11.73 engine on 13.73

visually the battery terminals look like they need cleaning.

 

The front ABS sensors can be cleaned (and the ring cleaned) or replaced without that much difficulty. See this video from the Toyota Master Tech known as the Car Care Nut. He has many great videos on YouTube.
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This short video focuses on just cleaning it
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Keep an eye on the battery. No load/lo-load 11.73 should be 12v+ . If it is aged, replacing it may eliminate a possible source.

Salim