In the underhood fuse box on the left side on the truck, check these:
LO HDLP LT fuse (10A)
(This fuse will only have power on it when the headlights are turned ON)
** The HDLP LO RELAY controls both headlight when they are on LOW, so if one light works on low this means that the HDLP LO RELAY is working properly.
Recheck for power at the low beam headlight socket on the YELLOW wire (remember to turn the headlights ON).
The BLACK wire on the low beam headlight socket is ground. Check to see if it provides a good ground. (This is how: connect the clip-lead of a testlight to the black terminal of the headlight socket [be careful not to damage the terminal] and touch the pick end [sharp end] to the POS battery terminal. If the light comes on, then the black has a good ground. If not, recheck your connections and try the "test" again. If it fails a second time, tract the black wire to find where the ground is interrupted.
You can do the same test with an voltmeter, however instead of having a light come on the meter will read battery voltage (usually between 12V - 14V).
Let me know how it turns out.
Friday, January 3rd, 2020 AT 6:46 PM
(Merged)