Test NTC-7A - Checking Oxygen Sensor (O2S) Switching

NOTE: Perform TEST NTC-1A before proceeding with this test. For connector terminal identification, see CONNECTOR IDENTIFICATION at beginning of article. For wiring diagrams, see WIRING DIAGRAMS at the end of this article. Perform TEST VER-2A after each repair.

Start engine and allow it to reach normal operating temperature. Using scan tool, read O2S state. If O2S state is switching, system is functioning properly. Test is complete. If O2S state is not switching, check if O2S is locked on lean (low voltage output). If O2S is locked on lean, go to TEST NTC-7B . If O2S is not locked on lean, go to next step.
WARNING: High fuel pressure may be present in fuel lines. Open fuel system with caution. See FUEL PRESSURE RELEASE procedure in this article.
Turn engine off. Connect fuel pressure gauge to fuel rail test port. Turn ignition on. Using scan tool, actuate fuel system. Allow fuel pressure gauge to stabilize to normal fuel pressure of 34-44 psi (2.3-3.1 kg/cm² ). Using scan tool, stop fuel system actuation. Monitor fuel pressure gauge for one minute. Go to next step.
If gauge pressure decreased more than 10 psi (.7 kg/cm² ), replace leaking fuel injector(s) or "O" rings as necessary. If gauge pressure decreased less than 10 psi (.7 kg/cm² ), inspect air cleaner and inlet ducts for restrictions. Repair as necessary. If no restrictions are observed, go to TEST NTC-13A .