Problem with DRL's

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by CP10KRK, Apr 11, 2013.

  1. CP10KRK

    CP10KRK New Member

    Hello Everyone. I'm a newbie (fng) here on the forum. I just bought my 99 Sierra 1500 last week and have discovered among other things, a problem with the DRL's.
    When I start the truck it seems my low beams are on,along with the tail lights. At night when I switch on the headlights, nothing changes. and it makes no difference what position I have the switch in, on or off. Even turning the lights off at night As long as the truck is running, all lights are working. I do have the sensor sticking up thru the dash not covered by anything. I looked for a cure on here, but no luck other than most people just pull the fuse? Any help is appreciated.
  2. pmf608

    pmf608 Epic Member 5+ Years 1000 Posts

    That sounds to me like your light sensor on the dashboard has stopped working and your truck always thinks it is dark so it just activates the automatic headlights all the time. This is the same as having the headlight switch in the on position. You could just leave it as it is, since the only real downside is slightly reduced bulb life, or replace the sensor to make it only turn on the DRLs during the day and automatically switch the headlights on at night.
  3. buckmeister2

    buckmeister2 Rockstar 4 Years 100 Posts

    That certainly could be it, PMF, but it sounds a lot to me like someone has possibly bypassed the sensor, leaving them on all the time. I did not think 99's had the auto-headlights (not the same as DRL). He says when he switches on the headlights, nothing changes...doesn't that mean the headlights are always on, which is not the same as our DRL's, right?

    The "low beams" are not the same as DRL's on a '99, if I recall.

    It was not uncommon at one time for an owner to wire the low beams to be on whenever the truck was running.
  4. pmf608

    pmf608 Epic Member 5+ Years 1000 Posts

    A bypassed sensor would be another possiblity. However, I think when people bypass it, they usually bypass it so that they can use the headlight switch for manual control of the headlights, making the truck always think it is daytime. This would make the DRLs come on by default during the day and at night and the headlights would stay off unless the headlight switch was turned to the on position.

    The 1999-2002 trucks should all be the same in terms of headlight & DRL operation. They had a separate DRL bulb that only comes on when the truck is not in park and the light sensor detects light. When the sensor detects that it is dark outside, it automatically switches the headlights on. Some U.S. trucks had the option of pushing the 'Dome Override' Button 4 times to turn off the DRLs or headlights, giving you manual control, and the Canadian ones like mine did not let you manually turn off the headlights or DRLs. What's happening in this case isn't actually a malfunction of the DRLs. It is most likely a faulty/disconnected light sensor, or a previous owner took an unusual approach to bypassing the light sensor.
  5. j cat

    j cat Epic Member 5+ Years 1000 Posts

    what the problem is as time passes this sensor does not read light any more. it is a gradual decline . with you vin # go to dealer and get the proper dash light sensor and that is the fix ..this is a well known failure at your vehicles age.

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