Fault code C1A6A
Thread Starter
Driver School Candidate
Joined: Sep 2022
Posts: 15
Likes: 3
From: England
5th Gear
Joined: Mar 2023
Posts: 5
Likes: 1
From: Kansas
I'm running into the same issue، hit a dearlight, front passenger side headlight replaced, getting the C1A6A error code and the dealership wants to charge me 20k to replace the pre-crash ECU and other systems. Even though everything worked fine before replacing the headlight, now my LKA and auto high beam don't work at night, but LKA works fine during the day.
any thoughts/ ideas ?
any thoughts/ ideas ?
Pole Position
Joined: Aug 2020
Posts: 2,859
Likes: 1,004
From: NH
I'm running into the same issue، hit a dearlight, front passenger side headlight replaced, getting the C1A6A error code and the dealership wants to charge me 20k to replace the pre-crash ECU and other systems. Even though everything worked fine before replacing the headlight, now my LKA and auto high beam don't work at night, but LKA works fine during the day.
any thoughts/ ideas ?
any thoughts/ ideas ?
Thread Starter
Driver School Candidate
Joined: Sep 2022
Posts: 15
Likes: 3
From: England
I'm running into the same issue، hit a dearlight, front passenger side headlight replaced, getting the C1A6A error code and the dealership wants to charge me 20k to replace the pre-crash ECU and other systems. Even though everything worked fine before replacing the headlight, now my LKA and auto high beam don't work at night, but LKA works fine during the day.
any thoughts/ ideas ?
any thoughts/ ideas ?
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5th Gear
Joined: Mar 2023
Posts: 5
Likes: 1
From: Kansas
And yeah, I do not trust the dealer diagnosis
they charged me 2 grand just to tell me I need to replace the entire system for 20 grand.
5th Gear
Joined: Mar 2023
Posts: 5
Likes: 1
From: Kansas
Hi after much head scratching from two lexus dealers it appears the new headlight assemblies are supplied without a crutial part i.e. a halogen bulb inside the headlight. Remove the large grey coloured cap on the back of the headlight and see if there is a wire with plug attached hanging loose and a hole for a halogen bulb to go. Is so this could be the cause of the code. Every body assumed the unit was complete but it isn't. Check this and see.
and the headlight was ordered using my VIN number through the dealership, brand new, cost over 4k. At first they said it was the wrong part but confirmed it has the IR thingy and I tested it using techstream.
Thread Starter
Driver School Candidate
Joined: Sep 2022
Posts: 15
Likes: 3
From: England
thank you kind sir, Ill check that today and post.my findings.
and the headlight was ordered using my VIN number through the dealership, brand new, cost over 4k. At first they said it was the wrong part but confirmed it has the IR thingy and I tested it using techstream.
and the headlight was ordered using my VIN number through the dealership, brand new, cost over 4k. At first they said it was the wrong part but confirmed it has the IR thingy and I tested it using techstream.
Instructor
Joined: Sep 2021
Posts: 1,145
Likes: 602
From: VA
Ok, check bulbs as Tony suggested first. But thing is there was this subtle headlight engineering design change that is not reflected in manuals properly but which directly affects c1a6a.
Also - was JUST the headlight replaced? I mean no harness repair or replacement? Any aux parts?
Also - was JUST the headlight replaced? I mean no harness repair or replacement? Any aux parts?
9th Gear
Joined: Jan 2015
Posts: 9
Likes: 2
From: CA
Sorry to drag this from the dead. But same issue here:
Included time at 17:45 so you can see how to diagnose it in under 5 minutes.
As these cars age and it makes more sense to DIY a lot of these problems, I like to update older threads with more detailed information. Esp if you have the subscription to TIS and the diagnosis tool (which a lot more folks do today)
Earlier on on the video at 9 minutes, he goes on to describe the pre-collision system, how it works, as well as how the test procedure works w/ the diag tool.
But to test by yourself, the conditions for it to occur when your car is equipped with infrared pre-collision, is to drive at night at speeds greater than >11 MPH. The Halogen infrared bulb in the large projector turns on at that point (it's hard to see it turn on when the two smaller headlights are on).
Hope this helps anyone who's just first getting into diagnosing problems like this!
PS-Also icing on the cake, the dealer didn't realize that the valley plate was leaking and the car was due for automatic transmission fluid change. Dealers aren't what they used to be, be skeptical and do your own due diligence!
Included time at 17:45 so you can see how to diagnose it in under 5 minutes.
As these cars age and it makes more sense to DIY a lot of these problems, I like to update older threads with more detailed information. Esp if you have the subscription to TIS and the diagnosis tool (which a lot more folks do today)
Earlier on on the video at 9 minutes, he goes on to describe the pre-collision system, how it works, as well as how the test procedure works w/ the diag tool.
But to test by yourself, the conditions for it to occur when your car is equipped with infrared pre-collision, is to drive at night at speeds greater than >11 MPH. The Halogen infrared bulb in the large projector turns on at that point (it's hard to see it turn on when the two smaller headlights are on).
Hope this helps anyone who's just first getting into diagnosing problems like this!
PS-Also icing on the cake, the dealer didn't realize that the valley plate was leaking and the car was due for automatic transmission fluid change. Dealers aren't what they used to be, be skeptical and do your own due diligence!