Test NF-6A - Checking Oxygen (O2) Sensor Switching
- Allow engine to reach normal operating temperature. Using DRB-II, read O2 sensor state for one minute (at idle). If O2 sensor state is switching (rich to lean), system is functioning properly. Test is complete. If O2 sensor state is not switching, check if O2 sensor is locked on lean. If O2 sensor is locked on lean, perform TEST NF-6B. If O2 sensor is not locked on lean, go to next step.
- Turn engine off. Allow engine to "hot soak" for 5 minutes. Remove spark plugs, keeping them in order according to cylinder. Inspect spark plugs for wet tips or fuel fouling.
- If ANY spark plug is wet or fuel fouled, replace leaking injector(s) at corresponding cylinder(s). Perform VERIFICATION TEST VER-3 . If NO spark plug is wet or fuel fouled, inspect air cleaner filter and inlet ducts for restrictions. Clean or repair as necessary. Perform VERIFICATION TEST VER-3 . If no restrictions exist, perform TEST NF-11A .