Changed the bulbs, checked the fuses, and replaced the switch in the 2004 suzuki forenza. Low beams still out. Need the wiring harness location to check it out.

If you have the HID bulbs check with an Autoparts store like Autozone. I believe the right and left headlights have separate Relays in the Powerbox. It is possible that there are 2 low beam and 2 high beam relays total. They pull too much power for both sides to be wired together and may wire the high beams separate too!

Suzuki has a recall on head light wiring harness mine had same problem

The Module for the DRL is most likely bad, the DRL Module is squarish in shape and Black in color and would be located in the fuse area or in the engine compartment. Just pull it straight out and purchase another one and re-install. Buying new low-beam lights will not solve the problem, because if your low-beams work when you turn on your headlights than it is not your bulbs. The DRL Module uses your low beam lights, but at a lower intensity than when it is normally on, so if your low beams work when you turn on the headlight switch than your DRL Module is bad.

I would suspect its more likely a fuse or the hi - low switch than the wiring harness, or perhaps the bulbs went out simultaneously. I would check or have these checked before I go as far as replacing a wiring harness.

You should check the dimmer switch.It is the switch that is totally in charge of high and low headlight functions.

replace the switch

still could be just two headlight bulbs you need to check that you are getting power to the bulbs

fuse #38 on the inside inside fuse panel was blown on mine, replaced and lights work fine.

I have a 2006 Suzuki Forenza with the same exact error, I had to replace fuse box. Now it is working, but it costed me almost $ 500.

I would look at the relay contact and connector for signs of corrosion or poor conduction. The relay may be okay but the terminals often get enough corrosion to interfere with electrical conduction.