Fuel Pump Feedback
WARNING: This page is about a different car, the 2003 GMC Sierra and 2003 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The PCM monitors the voltage on the fuel pump relay control circuit. If control module detects an incorrect voltage on the fuel pump relay control circuit, a fuel pump relay control DTC sets. To diagnose, see SELF-DIAGNOSTICS - 4.3L SIERRA & SILVERADO article.