Checking HO2S Sensor Signal

Oxygen Sensor Connectors 20v:

- Fold back rubber boot at oxygen sensor lead 1, do not separate connectors.
- Connect Digital Volt Ohm Multimeter (DVOM) between exposed sensor lead and ground.
^ DVOM should oscillate between 0.1 and 0.9 Volts
- If reading is fixed at 0.4 - 0.6 Volts, check for open circuit between sensor and ECM.
- If reading is too low, check for grounded signal wire, intake leak, or heater element operation.
- If reading is too high, check for signal lead short to other wiring.
- If wiring is OK, replace sensor and recheck.