Geely EC718 2009 Workshop Manual page 672

2-590 Control System JL4G15-D
7. Oxygen Sensor (HO2S)
Oxygen sensor is an important sensor in a close-loop fuel
control system, which adjusts and maintains the ideal Air-Fuel
ratio, so that three-way catalytic converter achieves the best
conversion efficiency. When the mixture Air-Fuel ratio
becomes lean, the oxygen content in the exhaust increases,
and oxygen sensor output voltage is reduced. On the contrary,
the output voltage increase feedback to ECM indicates the air-
fuel ratio.
Oxygen sensor sensing material is zirconia, hollow with an
external sensing part. When Zirconia components are heated,
they are activated, reference air enters the hollow parts of
zirconium oxide from the wire. Exhaust passes through the
outer electrode, oxygen ions move from the center of zirconia
to the outer electrode, thus consisting a simple atomic battery
with a voltage between two electrodes. According to the
oxygen concentration in the exhaust, Zirconium oxide changes
the output voltage, and thus determining the oxygen content in
the exhaust. Usually the exhaust oxygen sensor design
generates a voltage amplitude jump in the vicinity of the Air-
Fuel ratio (14.6:1) to help ECM to determine the exact Air-Fuel
ratio. Pre-Catalytic oxygen sensor is installed in the exhaust
manifold, the three-way catalytic converter front end. Post-
Catalytic oxygen sensor is installed in the three-way catalytic
converter rear end. When the mixture is rich, the output voltage
is 750 mV. When the mixture is lean, the output voltage is less
than 200 mV. When the mixture becomes rich from lean, the
responding time is less than 75 ms. When the mixture becomes
lean from rich, the responding time is less than 150 ms.
EC718/EC718RV EC715/EC715RV 10/2009
8. Fuel Injectors
FE02-5129b
The injector structure is an electromagnetic switch valve
device. The coil form poles leads to the engine wiring harness
and ECM and is connected to power supply. When the coil is
controlled by ECM to connect to the system ground, the
resulting magnetic force overcomes the spring force, fuel
pressure and manifold vacuum suction, and draws the valve
core. The fuel sprays through the valve seat hole to the guide
hole as a mist type spraying into the intake valve. When the
power supply is cut off, the magnetic force disappears, with the
spring force and fuel pressure, the injector closes.
The top of the fuel injector rubber seal and the fuel rail form a
reliable fuel pressure seal; the lower part of the same rubber
seal and the engine air intake manifold form an air seal. Fuel
injector resistance is 11.6-12.4 Ω.
Note
When the fuel injector is blocked or not closed tight, the
engine malfunction lamp may be lit, but the detection of
DTC code is: oxygen sensor distortion, erratic signal,
such as Air-Fuel ratio is not normal fault. At this time
component malfunction should be carefully judged.
Because when the fuel injector is blocked or leaking, the
amount of fuel injected is not controlled by the ECM pulse
width control. The oxygen sensor feedback to ECM will
be very different from the ECM control target. When ECM
detects this signal, it will determine the oxygen sensor is
not working properly. But the system can not determine
whether the fault is the oxygen sensor itself or other
associated parts. Therefore when diagnose such a
malfunction, the malfunction component must be
carefully identified.
Engine
FE02-5131b