I've got a 21 GX Base+Premium w/ Sport+, just turned 31K miles.

My wife was driving home the other day, and she said that the dash started beeping, and messages were rotating on the dash indicating errors/failures:
Pre-Collision System
Lane Departure
Cruise Control
Automatic High Beam

When she got home and parked it, upon restart no codes or errors were present. I took it for a drive and could not easily reproduce the errors.

After much testing, I seem to have narrowed things down to a (mostly) repeatable condition:
Driving while outside ambient is > 60 degrees F for some period of time. Sometimes minutes, sometimes up to an hour. Driving 100 miles while outside temp is in the 40s or 50s will not cause the problems to present themselves.

Wife did later admit that not long before it first happened, she was 'beating the top of a bottle of water against the side of the center console' to try to loosen the cap. Sigh.

All of the above errors tie into the front radar sensor in the grille. I pulled a code of C1A10 from the computer while it was running and that condition was present, but every time I cycle the ignition the errors reset themselves or go away. CEL light *never* illuminates.

I'm thinking it's something thermal - perhaps the sensor is in an early stage of failure? Does anyone know of the failure rate of these things? I can't imagine the 'percussive attack' on the center console area actually plays a role here, but I don't know what all connections are near that area.

I'm hesitant to take to dealer unless I can absolutely reproduce the issue, and so far I can only 'mostly' reproduce, but not always.

Thoughts? Ideas?

 

Found this from another Lexus Forum for LS,

C1A11 mean that the front millimeter wave radar sensor assembly's beam axis is deviated. You need to go to your Lexus dealer and ask then to perform a millimeter wave radar sensor adjustment. If you have APCS they will also have to adjust the object recognition camera as part of this procedure. If that failed you will have to replace the driving support ECU, which is not that hard but I highly doubt that this is the problem in that case. There is a bunch of used ECU on the market you can buy for a good price.

 

Same code for either issue

C1A0A; Front Radar Sensor Region Code Mismatch; 2020 - 2021 MY GX460 [08/2019 - ]

Last Modified: 10-23-2020 6.10:8.0.50 Doc ID: RM100000001JS0A

Model Year Start: 2020 Model: GX460 Prod Date Range: [08/2019 - ]

Title: PRE-COLLISION: PRE-COLLISION SYSTEM: C1A0A; Front Radar Sensor Region Code Mismatch; 2020 - 2021 MY GX460 [08/2019 - ]

DTC C1A0A Front Radar Sensor Region Code Mismatch

DESCRIPTION


The driving support ECU assembly uses the millimeter wave radar sensor assembly to detect objects in front of the vehicle.

Based on signals from the millimeter wave radar sensor assembly, the driving support ECU assembly calculates the possibility of a collision and operates the pre-collision system if it determines that the possibility is high.

When the millimeter wave radar sensor assembly is replaced with a new one, it acquires the country specification information from the driving support ECU assembly. Also, when the driving support ECU assembly is replaced with a new

one, it receives country specification information from the main body ECU (multiplex network body ECU). If country specification information in the millimeter wave radar sensor assembly, driving support ECU and/or main body ECU do not

match, DTC C1A0A will be stored.

C1A0A - Front Radar Sensor Region Code Mismatch -
When the engine switch is on (IG), the country specification information in the driving support ECU assembly and millimeter wave radar sensor assembly do not match for approximately 2 seconds or more.
Trouble Area: Main body ECU (multiplex network body ECU)

Driving support ECU assembly



CAUTION / NOTICE / HINT

NOTICE:

When replacing the driving support ECU assembly, always replace it with a new one. If a driving support ECU assembly which was installed to another vehicle is used, the information stored in the driving support ECU assembly will

not match the information from the vehicle. As a result, a DTC may be stored.

Recognition code registration is necessary when replacing the main body ECU (multiplex network body ECU).

If the main body ECU (multiplex network body ECU) is replaced, refer to Registration.

=============

OR----->Front Radar Sensor



When the engine switch is on (IG), the driving support ECU assembly receives an internal malfunction signal from the millimeter wave radar sensor assembly for approximately 0.2 seconds or more.



Millimeter wave radar sensor assembly

 

I took it in to my dealer last week for oil change and tire rotation, asked them to try to diagnose the errors I've only seen intermittently. Printed out the codes present when the errors display, service advisor said it would be immensely helpful to the tech... said he'd assign the vehicle to his foreman for this one.

Apparently they were able to reproduce the issue, either through a drive or whatever their Techstream diagnosis flowchart suggested they check. They also found other issues during inspection - both front shocks leaking, as well as the KDSS shock.

All said and done, both front shocks replaced, KDSS shock replaced, radar sensor replaced, and sharkfin antenna replaced (antenna replaced when it was observed that a Telematics code was also presenting intermittently). All under warranty. Paperwork shows it would have cost me about $6700 had I had to foot the bill myself. Ooof.

Only time will tell if everything is truly fixed - the radar issues only presented when ambient temp was > 65F or so. Around here, probably won't see those temps again until April/May 2025. (I'm 99% likely to buy the Lexus extended warranty before it expires though - waiting to hear back from Jerry)