Low beam headlight

116,285 MILES • 6.0L • V8 • 4WD • AUTOMATIC
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POORLUCKMAN
  • MEMBER
  • 1 POST
The low beams work when you unlock the truck but then turn off when you start the truck. Day/night does not matter they stay off. High beams, turn signals work.
Nov 20, 2018 at 4:15 AM
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JONNYB1963
  • ✓Experienced Mechanic
  • 263 POSTS
Hello,

To me it sounds like the low headlamp relay is bad, the relay is not getting power to the coil, or the the wiring between the coil and the Body Control Module is damaged.

Find the relay on the fuse block located under the hood on the left side of the engine compartment. Check to see if you can hear the relay click when someone turns the headlamps on and off manually. If there is no click then check the relay. See the link below for how.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

If the relay checks out good then you need to check the wiring to make sure its getting power and that the connection between it and the BCM is also good.

The reason the headlamps come on, is because the DRL powers the headlamps through a different circuit as you will see on the schematic.

See the diagram attached.
Nov 21, 2018 at 6:21 AM
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STRAILER
  • ✓Experienced Mechanic
  • 55,682 POSTS
Please let us know what you find.
Nov 27, 2018 at 10:51 AM
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