1999 Chevy Suburban

Voltage and ground, use a noid lite and check injector pulse, engine cranking. Check for voltage at injector key on. The computer controls injector ground circuit, on and off. If the computer doesn't see an rpm signal, no injector ground/pulse.

Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.