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I have a 99 Yukon. Sometimes the driving lights are on even though the light switch is in the off position (even during light hours) and sometimes they stay off . What controls this feature? Does the truck have some sort of light sensor or switch? When I first bought the truck months ago the lights were on a lot but they started staying off. Now they're staying on again. It's not a problem, but I'd like to know why.

Bill :cheers:

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Since I have a manual, my daytime running lights are on anytime the engine is running. The headlights themselves will come on when the sun starts going down or when I go through the drive-thru at the bank and the overhang casts a large shadow over the truck. :driving:

 

 

Oh, I also have an 06 Silverado, so it may be different but I think GM uses the same or similar sensors.

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A 99 Yukon is the old body style. The DRL's are not separate bulbs. They are essentially the low beam headlights. They are activated with the key in the run position, not the transmission like the new body style. Your low beams (DRL's) should be on whenever you turn the key on. The park and clearance lights should come on at dusk with the photo cell sensor (not sure where it is located on an OBS 99 Yukon). My dad's 99 Denali has auto headlights but I thought the photo cell was mounted on the rear view mirror. I can't remember. I need more info on your specific truck and if the DRL's are actually functioning all of the time or not. The DRL's are basically headlights on this particular truck. If they function correctly at night they should be on during the day.

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A 99 Yukon is the old body style.  The DRL's are not separate bulbs.  They are essentially the low beam headlights.  They are activated with the key in the run position, not the transmission like the new body style.  Your low beams (DRL's) should be on whenever you turn the key on.  The park and clearance lights should come on at dusk with the photo cell sensor (not sure where it is located on an OBS 99 Yukon).  My dad's 99 Denali has auto headlights but I thought the photo cell was mounted on the rear view mirror.  I can't remember.  I need more info on your specific truck and if the DRL's are actually functioning all of the time or not.  The DRL's are basically headlights on this particular truck.  If they function correctly at night they should be on during the day.

 

 

 

 

Exactly. I have a 98 Sierra. The DRL's are the low beam headlights. They should always be on when the key is on.

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Well, that's why I'm asking what controls the DRL (low beams). Mine operate inconsistantly. A couple of days ago they were on while I was driving to work in the morning....clear and sunny. Today the conditions were the same and they were off. Is something broken? If I knew what controls them I could check it.

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Well, that's why I'm asking what controls the DRL (low beams). Mine operate inconsistantly. A couple of days ago they were on while I was driving to work in the morning....clear and sunny. Today the conditions were the same and they were off. Is something broken? If I knew what controls them I could check it.

 

 

 

 

 

The first thing I would check is the override switch on your parking/emergency brake pedal. If it is this intermittant, then that is probably the culprit. On the newer trucks the headlights have relays. You may have a Relay on your fuse panel for the DRL's, but usually if a relay fails it does not work sporatically. I am not sure if there is a limit switch on the park brake pedal itself or not. I am guessing there is.

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  • 2 months later...

Hi,

New guy here....this is my problem also.

I have a 98 Sierra K2500.

The day running lights come on whenever the vehicle is running.

If the headlights are in the off position, the DRL are actually at approx

85% power...barely noticable difference.

When I bought my truck, I was told that if the parking brake pedal was

pushed in to the first click, the DRL would go off and not affect the brakes.

I found this to be true....no problem with brakes dragging on the first click.

However, I normally drive with them on.

My problem,, now, is that the DRL won't come on at all.

The parking brake is fully released. I get the little green indicator light

to let me know that the DRL are (supposed to be) on. But they are not.

The high and low beams work as they should. I'm pretty sure I checked

all my fuses and found them to be good....I'm at a loss.

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  • 4 months later...

On my 99, the DRL's are a seperate bulb from the headlights and I guarantee they aren't the low beams. My lights come on as soon I release the parking brake (I have a manual tranny). My DRL's are located right next to my turn indicators while the headlights are above them. The DRL light bulbs burn out as all bulbs do. I've had to change mine a few times.

 

Like asilverblazer said, there is a light sensor on your dash. It's in center of your dash close to the windshield. If you cover this with say a dashmat, then your headlights will be on all of the time because it's dark under that dashmat. The light sensor looks like a black nipple, you can't miss it if you look.

 

I personally love the automatic lights feature and the DRL's. At first I really didn't like them but now when I drive my wife's truck I miss them...

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