Oxygen Sensor

Air/Fuel Oxygen Exhaust
Ratio Sensor Voltage Gas Content

12.0:1 1.0 Volts [1] 5.0% CO [2]

13.0:1 0.85 Volts 3.8% CO [2]

14.0:1 0.65 Volts 1.3% CO [2]

14.7:1 0.45 Volts [5] 0.1% CO [2]

15.0:1 0.35 Volts 2.0% O2 [3]

16.0:1 0.25 Volts 3.0% O2 [3]

17.0:1 0.10 Volts [4] 4.0% O2 [3]




Remarks

[1] Full rich condition.
[2] CO: Carbon monoxide, is a sign of incomplete ignition, (not enough oxygen to burn all the hydrocarbons in cylinder).
[3] O2: Oxygen left over after all hydrocarbons have been burned.
[4] Full lean condition.
[5] Stoichiometric point: Output voltages below 0.45 volts indicate a lean condition, and output voltages over 0.45 volts indicate a rich condition.


NOTE: Both lean and rich conditions are usually accompanied by high Hydrocarbon (HC) readings. Due to not enough fuel, (lean misses), or too much fuel, (not enough oxygen to burn all hydrocarbons).