I'm driving a NX300h (2014) absolutely without any flaw since January 2015 for 84,000 miles. However...:

• On last Sunday, the audio system was blocked and couldn't been switched off, exactly as outlined in cb80923's post: https://www.clublexus.com/forums/nx-...ed-thread.html
• Half an hour later, it still was playing music, engine switched off and navi screen black. I could mute it by switching to Bluetooth source (only manip that worked). Music was quiet then.
• The day after, preparing for a long ride, the car didn't switch on, rattling sounds came from the front and rear and many error lights were blinking on the dashboard.
• I called the LEXUS 24h/24h service, and within less than an hour, the mechanic concluded on the 12V auxiliary battery being low on voltage: by connecting his starter kit according to the Lexus manual, the car started like a charm, albeit with many error messages and lights being displayed... Most likely, the abnormal audio system behavior (locked "on") depleted the 12V battery overnight.
• The mechanic advised me to start my long ride, allowing the auxiliary battery to completely charge; the error messages would disappear after half an hour.
• The car behaved absolutely normal, but the safety features like adaptive cruise control, AWD etc. remained inoperative.
• So I called my LEXUS dealer, who advised to bring my car to his shop, what I did.
• Two hours later, the supervisor called me to tell that the ECU was damaged, ("the first he saw in his entire career").
• Two days later I was informed that LEXUS would take over the repair as goodwill, even if my car was out of warranty, given the highly unusual character of the fault.
• On Friday, LEXUS informed me that it would NOT take over any cost, and that the cost of a new ECU would be 4500 US$, plus 1140 US$ manpower; my total cost would be 5640 US$ !!!

Questions:

• Are there any known similar issues?
• If yes, what was the total cost of repair?

 

Are you still under warranty or not? That is the only question that needs to be answered.
If you were out of warranty - well, you are out of luck.
Besides, it all sounds like a simple system reflash after 12V failure.
You did have 12V replaced, didn't you?

 

I'm out of warranty, and out of luck. This I know! I should have bought a 5-year warranty extension, but given the claimed Lexus reliability stats, I wrongly concluded this wasn't required.
What has been done to my car in the workshop, no one would tell you. The 12V battery doesn't seem to be the cause, the supervisor concluded on the ECU's death "as the diagnosis tool doesn't communicate with the ECU anymore". For the same reason, he can't reset & reflash the system, he says.
He also suspects potential voltage spikes happening when the troubleshooter connected his charging kit... (Oh my...).
My main question is how common this fault is, and if the cost of repair is reasonable?
And more generally: I just want to understand what happened

 

The workshop supervisor opened the (presumed) failed ECU, and showed an area on the electronic circuit what he believes is the result of heat damage (see encircled areas in yellow; the left hand side of the photo is a mirror showing the electronic circuit in a different perspective). All visible electronic components are in a pristine condition & no smell... Any comments?

 

Larger view of presumed overtemperature:

 

by connecting his starter kit according to the Lexus manual...

Were you present when this jump start was performed? It can
be done under the hood with the Positive (Red) connector in
the fuse box and any heavy metal ground or more laboriously
by accessing the 12v battery in the back.

If this was done backwards, however briefly, they may have
caused this failure.

 

Yes, I was partially present when the troubleshooter opened the fuse box and showed me a screw on the motor bloc where he intended to connect the 2nd cable. He didn't want to access the 12V battery in the back directly. However, I was at the side of the car when he connected the cables, so I can't tell unfortunately if he briefly attempted a wrong polarity. I was more than happy when the engine started.

You're right: the Lexus supervisor mentioned this possibility, and he told having seen several electronic failures happening when backwards polarity was applied, albeit not on ECUs.

… and it was a Lexus mandated company performing the jump start...! He told me that this company has an insurance against professional mishaps. The tough part would be to get evidence on this, and my Lexus dealer isn't quite active in communicating with these people, I'm afraid.

To my knowledge, every ECU nowadays has 1) a reverse polarity protection diode, and 2) a transient voltage protection system (TVS) to protect against high voltage spikes. Given the outstanding Lexus reliability stats (well, I'm the exception it seems), I can't believe the Lexus electronics engineers haven't provided these quite basic safety features.

 

some shady or smart people take their car and smash it into tree and then get all fixed under insurance...usually very expensive cars that break...

 

I'm not sure I'd like to drive a complex car restored to life after a serious crash, not so much from the mechanical but rather the electronics point-of-view.

Car dealers don't employ IT or electronics experts, but mechanics trained at best to run a diagnosis tool and send the test result to some headquarter analysing the error codes and giving some recommendations on what to do. Don't expect more finesse: I suspect the recommendation is in many cases (in my case for sure) to replace the whole damned module rather than fiddling around with wires, data analysers or oscilloscopes. This makes the repair so expensive: ECUs aren't repaired but replaced with new modules, even when a trained electronics expert could do more. I even suspect the diagnosis tools aren't providing a great depth of analysing complex faults.

And major repairs in car electronics often lead to a string of intermittently recurring glitches, errors and strange subsequent behaviors. But...there is nothing wrong in hoping for the best if you are prepared for the worst.

My point is: what can't be maintained at reasonable cost must not fail out of the blue, after 4.5 years! If it fails, even when the car is out of warranty, the manufacturer should at least contribute to some extent to the cost of repair. After all, his reputation is at stake as customers talk to each other.

 

Using fuse box bus is PROPER procedure to jump start that vehicle. Hybrids are not jumped off 12V in the trunk. So they didn't do wrong there.
I have a stupid question. Can some smart kid with soldering iron to re solder the damaged components or even replace some? After all, it's just parts.

 

That was my first thought too. But... there aren't any visible damaged components on the electronic board: all looks fine, and what the supervisor claims to be a "heat damage" is just normal soldering flux (brownish color). Behind this "area of concern" aren't any components either, just a Molex connector connecting the board to the rest of the module. I'm convinced there are smart people around perfectly able to repair a failed ECU, but then comes the reprogramming part: to my knowledge, Lexus (or other brands) don't share this proprietary software.

As far as I've been told, the diagnosis tool "doesn't recognize the ECU anymore",... "and it is our responsibility to decide on how to repair". Unfortunately this is how far I could go in getting answers.

"Sales people sell dreams, field engineers fix nightmares"

 

New ECUs are apparently available in the States for less than US$1000. Refer to the URL copied directly below.

https://www.lexuspartsnow.com/oem-le...odel=&Filter=()
Perhaps you could pay a Lexus technician privately to install it for you and load the latest firmware updates applicable to your country.
Another possible option is to locate another Dealer in Europe who will sell you the replacement part at a lower price.

 

Thank you n0v8or, this is the answer to one of my most important questions whether 4500 US$ for an ECU is reasonable or not. The dealer you mention sells genuine original Lexus parts, and the part I need for my car (an AYZ15L) would be Lexus Part No.: 89661-78190, retail price 983 US$ (discount price 739 US$), manhours to install and reprogram it coming on top.

I still have to overcome my shock seeing my dealer selling the unit at close to a 450% higher price to his loyal customer... Here we aren't talking about a few per cents!

Another good news is no other forum member seems to have experienced a similar ECU failure, restoring some faith in Lexus' reliability stats.

 

I just ordered a 2020 NX300h to replace my 2016 NX200t Fsport. I hope I dont see such ECU failure in mine.

Good luck and I will keep an eye about your progress and I hope it is a one of incident that could perhaps is a flaw/defect that has not been documented.

 

Here in the US body shops can salvage ECU's and things like that from wrecked and totalled NX's and install for half the price of new..You may want to look into that direction. Also after 84k miles this may be a good time to get a full aftermarket head unit from crutchfield or something that will do it all .. BT, carplay/android auto, reverse cam etc)..