01 duramax light issue

[Austin7e]

I got a 2001 Chevy 2500hd an the passenger bulb went out I replaced it an when i plugged it in all 4 headlights came on but the highs were as dim as the daytime running lights if I unplugged it the driver side was fine but when I plugged it back in it still did it. I tried different bulbs the problem still occurs any ideas what it could be. I think it's something on the passenger side but not sure

[Doug_Scott]

Dim headlights are almost always a bad ground issue. To verify, check the voltage at the headlight with the wire connected to headlight. If you are seeing battery voltage at the headlight on the power side of connector, then the ground side is likely loose or dirty. You must test this with the headlights connected to get a proper diagnostic reading. If you get a voltage reading on the ground side of the plug at the headlight, with it connected and turned on, then you know for sure there is a bad ground connection.