Low beams not working

[Dewhittier]

Hi. I have a 2003 Pontiac Vibe that I bought new it's been a great car but the first few years that I had it the lights would go on when you turn on the key but now it doesn't also the low beams don't work I checked out the fuses and bulbs but everything was good. Any suggestions on what could be the issue?
Thank you for your time.
Sincerely David Whittier

[joatmon]

Welcome to genvibe

I've had a number of headlight bulbs lose the low beam filament while the high beam filament still worked, some looked fine visually. Are you sure the bulbs are good?

If they are, then when you manually turn the headlights on, does the green headlight indicator light up in the instrument cluster?

[sarasvibe]

joatmon--

Yes that happened to a couple of my headlight bulbs a few years back on my 2009... removed the headlight bulb and you could see high beam filament was fine, low beam was broken.

For me the weirdest thing was that it was always the driver side bulb, not the passenger side... you'd think they have the same operating time...

[Dewhittier]

Both bulbs are good and the light doesn't turn on when I turn the headlights on it just has a light that turns on saying that the high beams are on.
Thanks for your suggestions

[joatmon]

I attached a wiring diagram for a 2003 Matrix headlight circuit, its the same as a Vibe except the matrix seems to have separate left and right headlight fuses

Assuming your high beams work, then that means that headlight relay and fuses are probably ok. I assume that the low beams don't work when you rotate the headlight switch to on (not just relying on the auto headlights)

The green indicator in the cluster to say the headlights are on full is actually an indicator to say that tail lights are on. (they don't come on when in DRL mode). This is controlled by the DRL module, sends a ground to the coil of the TAIL relay. The fact that the green indicator doesn't come on likely means that the tail lights aren't working, you'd want to verify that before driving at night, even with high beams.

The low beam filaments get 12V from the fuse/relays, but get their ground through the DRL module. When the low beams are on full bright, the DRL module gives them a good ground. When in DRL mode, the DRL module gives them some voltage above ground, so there isn't a full 12V across the filament, and they glow only half bright. I'd be inclined to suspect the DRL module, but I'm not sure what to offer as a way to verify other than just replace it.

One thing to check is the ECU-B fuse in the under dash fuse block