Generic TR 125 Service Manual page 147

16.2.7 Oxygen sensor
16.2.7.1 Working principle of oxygen sensor:
The sensor can be used to detect the amount of oxygen in the exhaust gas in the engine exhaust pipe for the
ECU internal fuel closed-loop control, so that the combustion of engine has always been maintained at the
most reasonable proportion of air and petrol.
16.2.7.2 Appearance of oxygen sensor:
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