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Does your truck always think it's night time? How to fix ambient light sensor issues.

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31K views 64 replies 34 participants last post by  pomarco  
#1 · (Edited)
Hi everyone,

As some of you know, I've been infuriated about how my truck always thinks it's night time. It would turn on the lights and dim the dash unless the sun was shining directly on the sensor. It could be broad daylight, not a cloud in the sky, so bright I'm wearing sunglasses...but if the sensor was in the shadow of the A pillar, roof, trees, anything...dark dash and lights on.

What. The. Heck.

A massive thank you to @hoitzed who pointed me down the right rabbit hole. It was very old, went to different forums, and had tons of conflicting information, so I thought I'd bring it to top of mind so everyone can fix it themselves. It is really easy, and hard to mess up. No special tools required. If you can swap your headlights to LED, you can do this. If you can swap your map and dome lights to LED...you'll be a pro! Disclosure - do this at your own risk. It's not covered under warranty if you mess something up, and don't blame me if you do...yes it's easy, but you're dealing with sensitive electronics, and if you're not comfortable with the risk, don't do it.

Step 1 - remove the sensor housing

The sensor housing is the little eyeball thingy in the very middle of your dash. It's held in place by a trapezoidal piece of trim, shown below (note that the sensor housing itself is not shown in this picture!). If you pry up on the front (facing the window, not you) part of the trim, it will pop up. Use something plastic to avoid scratching it. Once you've popped it out, you can remove the trim piece from the sensor housing by rotating it and then pulling it off...it's easy to see how to do this when it's exposed. Last but not least, unplug the sensor housing. You have to push quite firmly on the two side tabs to unlock it...just be patient and be firm yet gentle, and the plug will come off. I had to pull my sensor somewhat firmly and gently to get it out enough to reach the plug, it you can do it without trouble...gentle firmness and patience are the keys to step 1!

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Step 2 - Remove the sensor from the housing.
You'll want a small flathead or pick or something to depress small tabs in this step. The "bottom" of the sensor housing is one piece, that runs from the connector, to the rounded part. There are four tabs in total to press in to detach it. The first two are right at the edge of the connector (red circle), and you should do these first. The other two are midway up the rounded part and are a bit more difficult...depress one side, wiggle things so it can't reengage, then do the other side. Again, firm yet gentle. When you've separated the two housing halves, you can literally just pull the sensor out. It's a tight fight...I know I sound like a broken record, but be firm yet gentle!

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Step 3 - Marvel at how, for 6+ years, GM has been purposefully messing up the sensor, and continues to willfully ruin an otherwise well designed device.
Seriously...THEY COVER IT IN AN OPAQUE WHITE GOOP. Like, the sensor that's supposed to detect light? They block it from the light. WHAT?!
We're going to fix that by removing the goop. It is gross, and sticky, and nearly impossible to cut, so this is where it's a bit more of an art than a science. Take a deep breathe, crack a beer, and get to work...but before you do, read step 4 to see what the circles are all about.

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Step 4 - be thoughtful about what you want to do.
It turns out this sensor is actually a number of different sensors all on the one chip. My research tells me it does three things - blinks red when the alarm is active, measures the "solar load" to help the AC keep you cool, and measure the ambient light to dim the dash when it's dark out. We only want to affect the last one of these three things. Many, many other people just peeled all the goop off without issue...the AC might be a bit trigger happy but most people reported no issues, and the LED for your alarm might be a titch brighter, but who cares. I'm personally a bit of a stickler for perfection, and I did care, so I only wanted to remove the goop from the ambient light sensor. However, I wanted to clear as much of a path around them as possible, so light from any angle would trigger them.

In the photo above, the upper left side of the board is the "back" - the part that faces into the cabin when installed. Just remember that the connector pins always point to the right. The LED for the alarm is at the back, facing the cabin, where the red circle is. There are two solar load sensors - one on each side - in the middle, under the yellow circle. The ambient light sensors are at the front, under the blue circle, and there is again one on each side. We just want to uncover the front parts. Now, as I mentioned, this stuff is so goopy and sticky it's nearly impossible to cut. It's much easier to use a pair of tweezers, or even your finger nails, to pry little chunks off. Be very very careful that you DO NOT touch or scratch the circuit board or sensor with anything metal at all. Seriously, I know it's gross, but just use your fingers. I was able to slowly but surely pry away the front sensors entirely, as well as a nice "dome" around them. The solar load sensors are still mostly covered, and the LED is still completely covered. The two pics below show what I mean. You can do this too, or as noted above, you can just pull all the goop off (much easier, but may affect your AC).

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Step 5 - put everything back together.
No pictures here, it's very easy. Just literally reverse the previous steps...Slide the sensor back into the top of the housing. Clip the bottom half of the housing back in place. Plug everything back in. Slide and clock the trim piece that holds the housing on, and snap it back into place - insert the back part (facing the cabin) first, and then snap the front part back in...the exact opposite of how you took everything apart.

Step 6 - marvel at how the technology actually does what it should
Oh my gosh, it works. IT FREAKING WORKS. If it's dawn or dusk or really quite dark out, or of course night time, the truck turns on the light and dims the gauges and display. Just like it should. If it's sunny out or even a brighter cloudy day, it turns the lights off and brings the gauges /display to full daytime mode. It's gone from being 10% accurate to 95% - there's only been maybe one time where it was relatively dark in the morning, but still "daytime", that it took longer than I'd hoped to brighten things...but it's still a quite literal night and day improvement from before.

Good luck!
 
Discussion starter · #9 ·
Nice writeup ! Thanks. Moved it to the "How-To" section.

FWIW I believe that is white RTV, super common in electronics and also used in various other forms to make press-fit automobile gaskets.
Was it not already in the 2nd gen how to? It was supposed to be :p thanks!

And I could see it. It's super gross regardless.
 
Discussion starter · #13 ·
My annoyance isn't that it triggers night mode in a brief shade, but it stays triggered way too long after the full light is hitting it again. This tells me its probably a programming thing.
I just taught myself to turn the day running lights off to restore the full display light.
I thought so too but mine would stay off forever. It works much better after this change. I think the programming is sound, the gain on the sensor just isn't enough to trip the hysteresis back to the right value. Like it's always riding right on the edge of dark mode, instead of riding in the middle where it should.


It was in the 2 Gen Section...
But with your Editing
It changed the Thread..
And made an Excellent How To...
So ARC just was letting you know that and that as a Moderator we can move the Threads to correct location..
hehe yeah, I accidently clicked "publish" before I'd even started...between the wrong subforum and the early publish I swear I wasn't drinking :ROFLMAO: Thanks for getting it in the right spot!
 
Discussion starter · #16 ·
Nice writeup. I too was tired of the annoying, premature switch to night mode, so I gave this a shot, only I removed all of the “goop.” No issues at all. Haven’t driven the truck enough yet to fully gauge the improved accuracy, but I’m hoping your experience applies.

Note: When night mode inevitably switches on at dusk (and earlier), I typically turn the lights off to the left, then press the fog lights. I’m running the Gen5 harness, so this illuminates just the headlight LEDs and fog lights, which looks killer.

View attachment 440769
Great to hear that removing all of the goop worked for you! That's a gorgeous truck - looks very nice. Wish they'd had the blue available in the AT4.
 
Discussion starter · #19 ·
I can verify this works.

I tested it by covering the sensor with a folded up newspaper on a bright, sunny drive home, headlight switch on auto. Within 20 secs, the dash info center and the infotainment screen dimmed. I removed the newspaper and again, within 20 secs, it went back to full brightness. Before, it took a very, very long time to return to full brightness. Before, on a bright, sunny, cloudless day, if I was sitting at a stoplight and the sensor was blocked by the shadow of the A-piller, it would trigger the dash to dim. Today, after the mod, I tried to shade it to trigger it and it wouldn't dim. So, I'd say it's a success.

I modified mine the same as the OP, Dennon, and removed the gooey, sticky substance from the light sensor to the front of the truck.

Thanks for the research and write-up, Dennon! Well-done!
Glad to hear it went well for you! It's been an amazing change for me, very happy with it for sure.
 
Discussion starter · #24 ·
I need some help. I cannot get the trim piece out of the dash. What kind of tool did you guys use to pry it out? Also verify exactly where I need to pry. I appreciate your help.
Anything plastic will work. The key is that you must pry from the front, facing away from you and towards the window. I can take a pic if need be.