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Discussion Starter · #1 ·
My '08 Envoy SLT, in 'Auto Light' mode, keeps the low beams on continuously, 24/7. When at 11:30 O'Clock lights work correctly, shutting off after the expected delay.
Sounds to me like it's neither the switch nor Relay #46. that got replaced 3 yr,. ago.

Does LED Low Beams have anything to do with this? I can scarcely picture that being it.

Ambient Light Sensor replaced today with no change in behavior. Is it down to the BCM?

Thanks all . . .
 

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Discussion Starter · #2 ·
My '08 Envoy SLT, in 'Auto Light' mode, keeps the low beams on continuously, 24/7. When at 11:30 O'Clock lights work correctly, shutting off after the expected delay.
Sounds to me like it's neither the switch nor Relay #46. that got replaced 3 yr,. ago.

Does LED Low Beams have anything to do with this? I can scarcely picture that being it.

Ambient Light Sensor replaced today with no change in behavior. Is it down to the BCM?

Thanks all . . .
Update:

Set lights to Auto Night, unplugged upper connector of BCM,
LIGHTS WENT OUT!

Where's a good source?
 

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2004 chevy trailblazer_lt
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2,697 Posts
YES, the low beam LED have a great deal to do with what you are experiencing. The BCM is expecting to see a certain current draw for the low beam headlight. SInce it does not see the minimum current draw for the LED low beams that is programmed into it at the factory, it decides there is nothing to shut off so it does not send a shut off command to the low beams relay(s).

Lights in theses vehicles work in a different manner than what we are used to. Whenever you turn a light switch to on, it first goes to the BCM and the BCM decides based on other parameters it monitors whether or not to send an on command to the light circuit. If everything is OK, the BCM sends an "ON" command. If not, then it does not send an "ON" command. Same thing when you turn a light off. The switch sends a request to the BCM and if all is OK with the various parameters, then the BCM send an "OFF" command.

In your case, since there is not being enough current drawn, the BCM is being told something is not right so it does not send the "OFF" command to the low beams,

Also, the factory reflectors were not designed for LED bulbs and therefore you will not get the proper low beam headlight pattern being laid before the vehicle as you drive. Also, if not properly aimed, you could be blinding oncoming drivers going the other way.

My advice, go back to regular headlight bulbs. If you want something brighter, purchase a set of Sylvania SilverStar Ultras. Those do work well.

Good Luck!
 
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