High beams always on.

[Mickey_7106]

Wondering if someone can help fix this issue with my brothers 2001 tahoe. For a long time now his high beams stay on when the headlights are turned one. Pulling the multi switch to high beams does turn off low beams but when you switch back to lows the highs remain on. I've checked the headlamp relay and 2 fuses headlamp fuses under the hood. He's replaced the headlamp dimmer switch and multi purpose switch. Even with the bcm disconnected the high stay on. This is the only diagram i can find. Any help is appreciated

 

[exp500]

A Tech2 or similar would help you.
Check C1 and C4 Back to headlight relay, look at all relay pins w meter for voltage/ground.
Check light sensor , Scan BCM.

 

[Mickey_7106]

A Tech2 or similar would help you.
Check C1 and C4 Back to headlight relay, look at all relay pins w meter for voltage/ground.
Check light sensor , Scan BCM.

I don't have a tech 2. Forgot to mention relay is new. I would like to check b4 and c4 and c3, c1 but i don't know what or where those are.

 

[Mickey_7106]

Im not very good at reading these diagrams but i can get by enough. Most issues i have is i dont know what and where certain locations are ex. C4,b1 etc.
Is the headlamp switch and headlamp dimmer switch the same device (yellow)? Since both the highbeam signal and flash to pass from the bcm go to this dimmer switch I'll like to test that device (blue)

 

[Mickey_7106]

Update.
Pulled the drl relay just out of curiosity and it fixed the problem with the high beams. Now they work properly. Swapped the relay from another circuit and the light still work as normal. So, bad drl relay. Can't figute out how the drl and highbeams are tied in together. Thanks all

 

[Mickey_7106]

Alright lol
The drl relay was replaced and was working fine. Next morning it went back to high beams always on. We could just leave permanently remove the relay but i like tackling these problems for my learning experience in diagnosing. So, i signed up to autozones site to use their repair manuals. They seem to have a lot of info exept all the diagrams are extremely blurry at least on my mobile phone. Dowloading the image doesn't help. Does anyone have experience with the ebay repair manuals? I don't have a disc drive (mac) so something that could be downloaded to a thumb drive would be best.

 

[exp500]

Ebay manuals OK for under$30, keep a notepad handy for navigation.
Several times members have posted free links, likely expired now. You could search Duvk Duck.

 

[Colby_e32]

My truck occasionally does this. What I found was the terminal pins inside the fusebox for the headlights, and DRL relay are obviously a little worn.

I removed my relays, slightly bent the tabs outward, reinstalled them (tight fit) and its been fine for 6 months. My grandmas rough/bumpy dirt road/gravel driveway will occasionally cause it to act crazy again every few months.

Try it and see if it helps. Thanks