I have a 2001 Chevy S10 4x4 truck and the passenger headlight is dim. It is about 1/2 the illumination of the driver side headlight. Is this a relay or another problem?

The usual cause is a bad ground.
Check the ground with a test lamp.

bad connection or bad earth check all connection or bulb

I would check for the groundwire continuity

Driver side - dim low beams and no hi beam - Subaru Outback ...

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Oct 11, 2014 - Hi everyone, My drivers side headlights are dim on low, (car has separate bulbs ... When the headlight switch is turned ON, but for low beams, ...

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The high beam continues to work on both sides...I pulled the Driverside headlamp fuse and then both left and right beams lit up but very dim.

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Jan 23, 2014 - My driver's side lights are working fine - high and low beams. ... But it definitely looks like the big lamp on the driver's side gets brighter when ..... Drivers side headlight is very dim on low beam and goes out when on high beam ...

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Dec 11, 2002 - 6 posts - ‎4 authors

This sounds like there may be a short on the passenger side causing the circuit to draw more amperage than it should, thus dimming the headlights. try using an amp clamp on the blinker wire at different spots to see if the amperage jumps up.

It sure sounds like a bad ground Doug.

pinched/cut wire farther from the headlight socket.

May have also blown a fuse or damaged a relay.

dimmer switch bad

TEST
remove both bulbs from the lamps but leave them on their wires switch on and see if the bulbs are still different brightness if not they the passenger side lamp housing has damaged mirror is dirty or missalined and needs adjustment. if they are different brightness then this may be a earthing problem.

Sounds like your ground wire is broken (which could be broken, overheated, loose or corroded) If the color of the copper has changed(looks gray) or is corroded then you must replace the plug.

first i would want to know that all the headlamps are in good working order. it kind of sounds like these are also bad bulbs. you will also need to look for good ground wires just behind the headlamp assemblies. to answere your question, YES. if things were not repaired properly and without attention to detail then you could have wiring issues. on the plus side it doesnt sound too difficult. try these items first.