Locate the oxygen sensor on the exhaust system
Inspect the sensor and wiring for damage, corrosion, or loose connections
Check for trouble codes with an OBD-II scanner
Review live data from the oxygen sensor
Start the engine and let it reach operating temperature
Observe sensor voltage or air-fuel ratio readings
Verify the sensor switches rapidly on a narrowband sensor
Check that a wideband sensor responds smoothly to changes
Create a rich condition and confirm the reading changes
Create a lean condition and confirm the reading changes
Test the heater circuit with a multimeter
Measure sensor resistance if specified by the manufacturer
Check for exhaust leaks before the sensor
Compare readings between upstream and downstream sensors
Confirm the sensor responds within the specified time
Replace the sensor if readings are slow, stuck, or out of range