Oxygen Sensor (O2S)
WARNING: This page is about a different car, the 1995 GMC Sonoma and 1995 Chevrolet S10 Pickup. However, it is still accessible from the selected car via links, so may be relevant.
See ENGINE SENSORS & SWITCHES .
NOTE:
If injectors are dirty, they should be cleaned using approved injector cleaning procedure before performing port fuel INJECTOR BALANCE TEST.