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2005 Deville DTS
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Discussion Starter #1
We bought a 2005 Deville DTS and notice that the only way to turn the headlights off is to turn the twilight sensor switch all the way to off.
The dash keeps indicating headlamps suggested but we ignore it because it is bright Florida sunlight.
Of course being the person I am I would like to remedy the problem but have limited access to the electrical diagrams of the vehicle.
The Chiltons shows the sunload sensor connected between the headlamp switch and the instrument panel integration module.
Question I have is, where is the integration module? Is it behind the headlamp control?
Is there a common problem that I can check for?
The sensor looks like it would be a big problem to replace but first would like to check it from the dash area to see if it is any good.
Any help would be great as to common failure, things to check, and where the module is if not on or near the headlight control.
TIA
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,504 Posts
Use the Chilton to mop up oil spills. Find a real GM/Helm service manual set on eBay or www.helminc.com, or subscribe the car to www.alldatadiy.com.

If the headlights will not turn off in sunlight, with the Sentinel in use, then the sun sensor is either obstructed or has been punched down into the dash top. It's the 3/8" greenish disc in the driver's side of the windshield defrost grille. The two reddish lumps are the right and left sunload sensors for the HVAC system.

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2001 Cadillac DeVille DTS
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299 Posts
Did you check to make sure that your windshield wipers are turned off completely? If not, it might be on the lowest intermittent setting, which wouldn't turn the wipers on unless the sensor indicates that there is rain drops on the windshield.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Yep - good catch. The rainsense and headlights are set to operate together if the wiper stalk is not in the OFF position.

One very good reason that I use strictly manual control for wipers and headlamps - ??? Do you get a "headlamps suggested" message message when in shade or a garage or do the headlamps simply turn on ?
 

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2001 Cadillac DeVille DTS
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I had this happen to me when I first bought my car, and just like the OP, I thought something was wrong until I came on this forum and found the answer. This forum has helped me, so I wanted to pass that help along if I can.
 

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2005 Deville DTS
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Discussion Starter #6
Thanks for the suggestions. I will check the obvious items first that you all have suggested and then let you all know if it was one of those items. Thanks a lot!
 

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2005 Deville DTS
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Discussion Starter #7
Checked the above items. My DTS Deville has a sensor in the center of the dash at the front and looks like it is unhindered from the light.
Since I get the Headlights suggested when in manual no matter if it is light or dark my guess is it has something to do with the sensor.
Looks like a involved job to get the sensor replaced but will see what the dealer says. Could be a number of other things but I did check the
wipers to be sure they were manually off as well.
 

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1979 Coupe deVille, 1995 Sedan DeVille (sold)
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Read Submariner's post carefully. If it is in the center of the dash, you are probably looking at the HVAC sensor, not the headlight sensor.
 

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2005 Deville DTS
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Discussion Starter #9
I read his post very carefully and while some models may have it in the grill my 2005 deville DTS has a sensor in the dash
to the windshield side of the center speaker.
I also looked up the part on the web and it shows the same sensor I am looking at. It is a bubble type sensor called
a "Ambient Light Sensor" and mine looks just like it here http://www.partsgeek.com/catalog/2005/cadillac/deville/body_electrical/ambient_light_sensor.html
I am not sure where the confusion is but maybe others have it in a different location?
I sure hope I am not looking at the wrong sensor.
I did test the rain sensor in the rearview mirror with rain on the windshield while the wipers were in one of the
six modes and that worked fine. Still I turn them off.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,286 Posts
I read his post very carefully and while some models may have it in the grill my 2005 deville DTS has a sensor in the dash
to the windshield side of the center speaker.
I also looked up the part on the web and it shows the same sensor I am looking at. It is a bubble type sensor called
a "Ambient Light Sensor" and mine looks just like it here http://www.partsgeek.com/catalog/2005/cadillac/deville/body_electrical/ambient_light_sensor.html
I am not sure where the confusion is but maybe others have it in a different location?
I sure hope I am not looking at the wrong sensor.
I did test the rain sensor in the rearview mirror with rain on the windshield while the wipers were in one of the
six modes and that worked fine. Still I turn them off.
=============================


this - from page 3-19 of the 2005 Deville Owners Manual -

The light sensor for the DRL and the TwilightSentinel®
is located in the center of the front defogger grille.
If you cover the sensor, it will read “dark”
and the exterior lamps or the HEADLAMPS SUGGESTED message
will be displayed whenever the ignition is on.
 

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2001 Cadillac DeVille DTS
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299 Posts
I read his post very carefully and while some models may have it in the grill my 2005 deville DTS has a sensor in the dash
to the windshield side of the center speaker.
I also looked up the part on the web and it shows the same sensor I am looking at. It is a bubble type sensor called
a "Ambient Light Sensor" and mine looks just like it here http://www.partsgeek.com/catalog/2005/cadillac/deville/body_electrical/ambient_light_sensor.html
I am not sure where the confusion is but maybe others have it in a different location?
I sure hope I am not looking at the wrong sensor.
I did test the rain sensor in the rearview mirror with rain on the windshield while the wipers were in one of the
six modes and that worked fine. Still I turn them off.
I have a 2001 DTS and the sensor is in the center of the dash as you have described. However, if the sensor is faulty, I believe that it should throw a code since it seems like there's a DTC for just about every electrical part on the car.:yup:
 

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2005 Deville DTS
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Discussion Starter #12
I can cover the sensor and nothing happens. Doesn't make any difference if it is dark or bright sun it still indicates headlights are suggested.
Since I don't really know how to remove the grill without damaging it to replace it I will have to take it to a dealer and have them
resolve the problem. I am sure there is a tool to lift the grill without damaging it or marring it but I would hate to crack or break it.
After that I understand it is just a unplug, plug the new one in and twist it in the grill.
As for the DTC indications. I am using my small reader that sends data to my smart phone
and I have no codes indicated except a misfire which I get when I first start up sometimes.
Appreciate all the input as we are new to this car and just like it to be as good as we can make it. Thanks
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,286 Posts
I can cover the sensor and nothing happens. Doesn't make any difference if it is dark or bright sun it still indicates headlights are suggested.
Since I don't really know how to remove the grill without damaging it to replace it I will have to take it to a dealer and have them
resolve the problem. I am sure there is a tool to lift the grill without damaging it or marring it but I would hate to crack or break it.
After that I understand it is just a unplug, plug the new one in and twist it in the grill.
As for the DTC indications. I am using my small reader that sends data to my smart phone
and I have no codes indicated except a misfire which I get when I first start up sometimes.
Appreciate all the input as we are new to this car and just like it to be as good as we can make it. Thanks
=======================
the on-board scanner usually gives more complete codes
than hand-held units -
 
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