[How to] Switched AHL Delete 1999-2002 Silverado

gpking

Well-Known Member
How to install a switch to cancel the Automatic Headlight (AHL) feature on some 1999-2002 fullsize GMTs that GM decided didn't need to ever be able to turn off their headlights.

Note: Your DRLs will still come on while in gear.

Parts:
1x Switch
1x 1.5 kohm resistor

Difficulty:
Easy

Time:
Less than a day

Credit to someone else on some other forum for the idea, I just decided to do it and type it out.
  1. Disconnect the battery
  2. Remove the knee bolster panel to access the BCM
  3. Locate connector C3 (rightmost purple connector)
  4. Identify the white wire and the gray wire 2 positions to the right of the white wire (NOT the one next to the white wire)
  5. Shave enough insulation off the wires to make a good solder connection (or use t-taps)
  6. Connect your switch and resistor inline between the white and gray wires (see drawing below).
  7. Done. You can now finally turn off the headlights whenever you want (on a ~15 second delay since this just tricks the BCM into thinking it's daytime).
Operation:
  • Switch ON / Circuit CLOSED - AHL are CANCELLED, you may use the headlight switch manually if you wish
  • Switch OFF / Circuit OPEN - AHL operate normally, the headlight switch is worthless
AHL_delete.png

20191229_191055-s.jpgSnapchat-1248459962.jpg
 

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