Knock Sensor
Description
The knock sensor is attached to the cylinder block. The knock sensor is designed to detect engine vibration that is
caused by detonation.
Operation
When the knock sensor detects a knock in one of the cylinders, it sends an input signal to the Engine Control Module
(ECM). In response, the ECM retards ignition timing for all cylinders by a specified amount.
Knock sensors contain a piezoelectric material which constantly vibrates and sends an input voltage (signal) to the
ECM while the engine operates. As the intensity of the crystal’s vibration increases, the knock sensor output voltage
also increases.
The ECM ignores knock sensor input during engine idle conditions. Once the engine speed exceeds a specified
value, knock retard is allowed.
Removal & Installation
1. Disconnect the negative battery cable.
2. Disconnect the knock sensor electrical connector.
3. Remove the knock sensor retaining bolt (1) and
remove the knock sensor.
(Tighten: Knock sensor retaining bolt to 20 N·m)
4. Installation is in the reverse order of removal.
Oxygen Sensor
Description
This vehicle is equipped with two oxygen sensors (upstream oxygen sensor & downstream oxygen sensor). The oxy-
gen sensors are located before and after the three way catalyst. The oxygen sensors continually monitor the oxygen
level in the exhaust gas. The sensor is made of ceramic zirconia. The zirconia generates voltage from approximately
1 volt in richer conditions to 0 volt in leaner conditions.
Operation
The O
2
sensors produce voltages from 0 to 1 volt, depending upon the oxygen content of the exhaust gas. When a
large amount of oxygen is present (caused by a lean air/fuel mixture, can be caused by misfire and exhaust leaks),
the sensors produces a low voltage. When there is a lesser amount of oxygen present (caused by a rich air/fuel
mixture, can be caused by internal engine problems) it produces a higher voltage. By monitoring the oxygen content
and converting it to electrical voltage, the sensors act as a rich-lean switch.
The oxygen sensors are equipped with a heating element that keeps the sensors at proper operating temperature
during all operating modes. Maintaining correct sensor temperature at all times allows the system to enter into closed
loop operation sooner. Also, it allows the system to remain in closed loop operation during periods of extended idle.
Upstream Oxygen Sensor
The input from the upstream heated oxygen sensor tells the Engine Control Module (ECM) the oxygen content of the
exhaust gas. Based on this input, the ECM fine tunes the air-fuel ratio by adjusting injector pulse width.
ON-VEHICLE SERVICE
BESM030018
03–170
Chery Automobile Co., Ltd.
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