Maintenance Manual for Chery·Windcloud M7.9.7 EFI System
5. Oxygen Sensor
Purpose: this sensor is designed to provide
the information that if there is surplus
oxygen after full combustion of fuel, which
is injected into engine cylinder in the intake
air. ECU, when applying this information,
can carry out fuel quantitative closed-loop
control so as to achieve utmost conversion
and purification of the three major toxic
elements (HC, CO and NO
X) in the engine
exhaust with the application of three-way
catalytic converter.
Composition and principle: the sensing
element of oxygen sensor is a porous
ceramic pipe, the outer side of pipe wall is
surrounded by engine exhaust, while inner
side vents to atmosphere. According to
inside and outside oxygen concentration
difference, sensor figures out indirectly fuel
injection pulse width, and then transfers the
information to ECU, and the ECU controls
the injection again.
The working voltage of oxygen sensor
fluctuates between 0.1-0.9V, 5-8 variations
in 10 seconds is required; if lower than such
frequency value, it shows that the sensor is
aged, and needs replacement. The said
sensor is unrepairable.
Failure diagnosis: ECU monitors on
various sensors, actuators, power
amplification circuits and sensing circuits. In
case any of the following situations occurs,
failure mark of the oxygen sensor is set.
Accumulator voltage is unreliable
Manifold absolute pressure signal is
unreliable
Engine coolant temperature signal is
unreliable.
Injector driver stage failure
After oxygen sensor failure mark is set, fuel
quantification closed-loop control is shut
down, and the primitive fuel injection time
stored in ECU is used to carry out fuel
quantification.
Installation hints: the tightening torque of
oxygen sensor is 50-60Nm, a layer of rust
preventive oil shall be applied on oxygen
sensor after replacing so as to prevent from
incapable removal in case of rust.
Troubleshooting: mainly check if the plug
connection of several wires on the sensor is
in good condition, and if there is short
circuit or open circuit.
Generally, sensor damage is caused by
plumbum and phosphorus poisoning, so
pay attention to fuel quality, meanwhile
excessive consumption of engine oil is
liable to result in sensor failure.
Oxygen sensor
Main relay
Oxygen
sensor
Circuit diagram of oxygen sensor
Oxygen sensor has a cable, the other end of
which is electric connection. The outside of
sensor is wrapped with asbestos fireproof
covering.
There are 4 pins on the joint:
1# connecting with heating control
(ECU1#);
2# connecting with heating power and main
relay;
3# connecting with sensor ground
(ECU36#);
4# connecting with signal (
+) (ECU18#).
Interior structure of oxygen sensor
5
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