Where is the oil sending unit on a 1991 Chevy Silverado 4x4?

The oil pressure sending unit on a 1991 Chevy Silverado 4x4 is located on the passenger side of the engine block, near the oil filter. It's a relatively small unit with one or two wires connected to it. However, the exact position might vary slightly depending on the specific engine (e.g., a 5.7L, 6.2L, or 4.3L).

To be certain, it's best to consult a repair manual specific to your truck's engine. A Haynes or Chilton manual will have diagrams and detailed instructions. You can also find diagrams online by searching for "[Your Engine Size] 1991 Chevy Silverado Oil Pressure Sending Unit Location". Always be careful when working near hot engine components.