2005 3.8L No high beams

[Black_Blade]

Spent good part of yesterday trying to figure out why the high beams wouldn't work, will have to tackle it again today. Using schematics, found the wire that if we ground it, lights do come on, so no issue there. Read through the theory of operation on Alldata and tried to work through the circuit diagram, but the write up is not detailed enough to walk you through how all the various sections come into play.
Had spare parts from another known good donor and switched out parts as a hail mary but got nada. Switched out the dimmer switch, left hand fuse block (with the headlamp relay wonderfully located on the inside of it...really engineers?!?).

[Tech II]

So, your high beams don't work, but your low beams are ok? Does flash to pass function work?

Do high beams not work in manual as well as auto?

If the low beams work in manual, and flash to pass works, you need a multifunction switch.....

If flash to pass does not work, then there is an open in circuit 1200 or a bad multifunction switch....

[Black_Blade]

The low beams work, but have no high beams. Didn't think to try the flash to pass, was busy on another car today and didn't get back to it, but will see it that function works.

Not sure how that auto feature works, you mention Tech..I just pull out the headlight switch and then use the dimmer switch to try to get the high beams, the little high beam light in the cluster comes on but that's it.

I located the pink wire from the right headlight and then the same wire at the dimmer switch, thinking maybe there was a break in this ground line, but did an ohm test and it passed.

I had swapped out another known good MFS but still didn't help.

[SierraK1500]

Did anyone even think to check the relay? Got a clean connection to the relay block?
HHr had the same issue and it was the relay and the socket.

[Stealthee]

Originally Posted by SierraK1500

Did anyone even think to check the relay? Got a clean connection to the relay block?
HHr had the same issue and it was the relay and the socket.

This. I randomly lost my high beams one night and it turned out my relay had worked loose.

[Black_Blade]

Couldnt find any issues with relays or fuses. The mechanic I'm apprenticed under..his answer to the issue..run a separate wire with a switch on dash for high beams. (we work at cab company to keep fleet going so I guess looks aren't important not to mention figuring out what is wrong with the circuit..ah well)

[SierraK1500]

I would be very Leary of the mechanic you work with. The BCM controls all functions of the car. Might want to re-program it.

Don't rig the lights with a switch. All kinds of stuff can occur including a fire.

[strmn94]

i was told that a BCM can not be reprogrammed. if a BCM programming is going bad, it must be replaced and then flashed with the program for that vehicle. and it should be done at a dealer, because most other mechanics can not afford the techII and software for it. i would look at the connections, and wires to be sure they are good and no corrosion at teh plugs.