This is the "late" model (same as 2005-2008) style lariat w/ DRL and Auto lights.
Problem: Low Beams only not working

Checked so far:
1. No power to fuses 23/25 ... tested fuse in on top of posts.
2. Fuse 40 good to BSM - Pulled out and nothing from light switch works
3. Pulled out the MFS and checked circuit 15 in harness (Red/Ye) and have 10+ volts.
4. Hi Beams / Fog / Marker all work fine

I'm assuming it's my MFS switch. What can i "jump" to determine it's definitely the MFS before I shell out $100?

I've checked all the other answers here, especially from SSCULLY and I cannot determine based on previous answers.

Thanks in advance.

 

1. when you tested fuses #23 & #25 did you have the main headlamp switch in the on position ( not autolamp ) ?

2. When you are having the issue with the low beams, is it in the on or autolamp position ?

 

1. yes it was in the On position 2. It is actually both. Primarily, i have only been using the headlamp switch in the ON position (#1 in your diagrams) for diagnosing.

 

By the way... somehow i missed one of your posts (aha!!) and I just jumped the Red/Yellow and the Red/Black wires on the MFS connector and the low beams do infact work now when Headlight switch is in ON position. It's too bright to try the autolamp.

 

That is a strong indication that the MFS is the issue.

Time to pull the MFS and test the MFS itself to make sure it is not a connector issue.

 

You're awesome.... it's the culprit and and i ordered one from parts geek for $75 ... should be here in a few days. I'll put it in and keep the fingers crossed.

BTW: What book are you getting these diagrams from?

 

Having the same issue, but when I jumped the two wires, nothing. Where is the next thing I should check?