1996-2005 Suzuki DF40, DF50 Four Stroke Outboard Service Manual, Page 65Get this manual
ENGINE CONTROL SYSTEM 3-10 O2 SENSOR (Optional item) The O2 sensor is installed in the exhaust manifold only when the O2 feedback operation is performedThis sensor is zirconia element (platinum plated) the output voltage of which changes depending on the oxygen concentrationThe voltage change reflects the concentration of the oxygen in the exhaust gas and is used to perform the O2 feedback operationThe terminal voltage change (0 V) is dependent on the concentration of oxygen in the exhaust gasThis detected voltage value therefore represents the oxygen concentrationThe terminal voltage decreases when the oxygen concentration is high, and increases when it is low