How many o2 sensors are there on a 2003 Chevy silverado z71?

A 2003 Chevy Silverado Z71 typically has one upstream O2 sensor (before the catalytic converter) and one downstream O2 sensor (after the catalytic converter). Therefore, the total is two. However, it's always best to consult your vehicle's repair manual or a parts diagram specific to your truck's engine (4.3L, 4.8L, 5.3L, 6.0L, or 8.1L) to be absolutely certain. The number of sensors can vary slightly depending on the engine configuration and emissions standards.