2001 Chev Cavalier LS sedan. Low beam on right works, high beam does not, also high beam on left works, low beam does not. These problems both exist simultaneously. Therefore only one headlamp is on whether in hi or lo mode. Fuses, relays, wiring, bulbs have been repeatedly checked and appear to be intact and functioning. Flash to pass feature does work. Could there be a problem w/ the turn signal/hi/lo stalk switch?

did you replace the bulbs themselves

Someone will need to check for voltage at the dimmer switch and then trace back to the fuse box as needed.

The bulbs are grounded to the body, so if one ground wire is dead I would expect to find a break in the wire or at the connector. You should be able to splice into the wire and run a new one to a grounding bolt.

I would focus on the connections going to that head light for the low beam. I agree, it is not the switch, otherwise other side low beam would not be working. It is most likely bad bulb inlet( if it i separated bulbs for high and low) or it is the connection going to the low beam that operates it. Hope this helps. Don't waste your time on switch, it is not that.

First, be sure that the headlights are actually coming on. These cars have daytime running lights that use the headlight bulbs at a lower voltage. If the car is only using the daytime running lights, the tail lights will not be on with the headlights. The multifunction lever always turns on the high beams when you pull on it (it's called 'flash to pass'). Make sure the headlight switch is working, and also check the headlight circuit breaker.

probably best to work backwards:
the fuse itself will be fine if the lights come on at all, so at least at that point it should be fine.
first you'll want to check with a known good bulb (or put bulbs in another car [if available] to verify they are fine) to make sure you don't just have 2 burnt out low beams (high and low beams are separate filaments)

if the known good bulb still doesn't work (but normal high beams and DRL do) check the contact points where the bulb gets plugged in for any corrosion, then onto the wiring itself, feel the wires for any signs of damage; extra stiffness, very darkened areas, or very sharp bends/kinks (as much as you can reach)

the hi/low switch probly needs replacin-ur gonna need a svc manual-purchase one from parts place or fixya

faulty light switch or light control module

Fuse/Relay
Location
Fuse Amp
Rating
Passenger Compartment
Fuse Panel Description
9 10A Right Front Low Beam
10 5A Left Front Turn, Left Front Repeater, Left
Front Sidemarker, Left Front Park Lamps
11 10A Left Front High Beam
12 — Not Used
13 5A Cluster
14 10A RCM, DATC
15 5A Not Used (Spare)
16 5A E/C Mirror, Heated Seat Controls, RSM
(Rain Sensor Module)
17 5A RCM, Alternator Warning Lamp
18 20A Radio, CIA
19 15A Tilt/Tele Motors
20 10A FEM, DATC, Cluster, Brake Shift Interlock,
REM
21 10A Power Folding Mirrors
22 10A DDM
23 10A Right Front High Beam
24 5A PATS
25 10A Left Front Low Beam
26 10A Wiper Relay, Windshield Washer
27 10A Radio, Cellphone
28 5A Security Horn
29 5A Trailer Tow Ignition Sense, VEMS, FEM
30 5A FEM
31 — Not Used
32 20A Cigar Lighter
33 10A Switch Backlighting
34 10A Not Used (Spare)
35 5A Stop Lamp Signal