For anyone who wants to get more details on actual O2 sensor operation I have come across several
Society of Automotive (SAE) articles that give the intimate details on their operation. This stuff
is great for those nights when you have trouble falling asleep. Your local Library should have the
articles on micro-fiche.
SAE article # 930352 "Static Characteristics of ZrO2 Exhaust Gas Oxygen Sensors"
Ford Motor Co.
SAE #930388 "A Feedback A/F Control System for Low Emission Vehicles"
M.J. Anderson. Ford Motor Co.
SAE # 830986 "An Engine Dynamometer Study of the A/F Compatibility between a Three-Way
Catalyst and an Exhaust Gas Oxygen Sensor"
I am not sure what John means with the idea that there is excess oxygen in the exhaust with a
"Rich" mixture and less oxygen with a "Lean" mixture. All the documentation I have shows less
O2 with Rich mixtures (higher O2 sensor voltage) and more O2 (less O2 sensor voltage) with Lean
If the Air/fuel ratio is increasing with lean mixtures are we not passing more air through the
exhaust? The lambda "excess-air" factor increases with lean mixtures.
The 4 gas exhaust analyzer I've tested uses the O2 reading (less than 1% = rich, greater than 2%
indicates too lean) to help diagnose emission and engine performance problems. Engine misfires will
actually raise the exhaust O2 level as the O2 is passing through the misfiring cylinder without
>No, the oxygen sensor uses a special ceramic material which generates
>a voltage up to one volt when oxygen is present. Contrary to what many
>believe, the amount of O2 in the exhaust increases as the mixture
>gets richer (lambda less than one), not as it gets leaner (lambda greater
>than one). Lambda represents the excess-air ratio and is equal to
>one when the mixture is stoichiometric.