Sym HD2 125 - Page 73

5. Fuel Injection System
5-10
O2 Sensor
Function
O
2
Sensor measures the proportion of oxygen in the exhaust gas, sending signals to ECU which adjusts
the air-fuel ratio by changing the fuel injection time. If the proportion of oxygen is too low, it means the rich
air-fuel mixture with higher HC & CO concentration in the exhaust gas. If the proportion of oxygen is too
high, it means the lean air-fuel mixture with higher temperature and higher NOx concentration.
1. O
2
Sensor outputs feedback signal to ECU which keeps the air-fuel mixture near the stoichometric ratio
approximately 14.6 and forms the closed loop control system.
2. When the air-fuel mixture is near the stoichometic ratio, CO / HC / NOx are converted most efficiently.
3. O
2
Sensor heater resistance: 6.7 ~ 10.5 Ω
4. O
2
Sensor amendment in the voltage value: between 100 ~ 900 mV
O2 Senso
r
Output voltage
Rich ← 14.7 → Lean
1. Ceramics tube
2. Electrode
3. Emissions
4. Atmosphere
3
1
2
4
ECU
Battery
Power relay
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O
2 Senso
r