2.12.2.2 Components Description
1. Engine Control Module (ECM)
Engine control module is a microprocessor with a single chip as the core. Its function is to process
data from various vehicle sensors to determine the engine's working condition, and controls each
engine actuator through various actuators.
ECM normal work voltage 9.0 V–16 V
Notes:
Although ECM has the over-voltage and reverse polarity voltage protection function, during the
repair process it is prohibited to connect the battery positive and negative wrong or apply voltage
higher than 15 V. Otherwise, it will cause damage to ECM and other electrical equipments.
2. Crankshaft Position Sensor
The crankshaft position sensor output can be used to determine crankshaft position and rotation
speed. The engine rotation speed and crankshaft position sensor are magnetic-electric sensors
installed near the crankshaft. When the crankshaft rotates, they work together with the 58X gear
on the crankshaft. The 58x tooth top and the alveolar pass through the sensor in different distances
when the crankshaft rotates. The sensor senses the reluctance change; the alternating reluctance
generates an alternating output signal. The 58x gear plate gap position aligns with engine top dead
center. When the cylinder No.1 reaches top dead center, the sensor aligns with the 20th tooth lower
edge. ECM uses this signal to determine crankshaft position and rotation speed.
Resistance Value of the sensor: 20-30℃(68-86℉)900-1100Ω.
Output Voltage: 400 mV at 60 rpm. The voltage increases as the speed increases.
3. Intake Air Pressure/Temperature Sensor:
This sensor detects intake manifold pressure change caused by engine load and speed changes.
These changes will be converted to the voltage output. When the engine decelerates, the throttle
body closes to result in a relatively low intake manifold absolute pressure output. Intake manifold
absolute pressure and vacuum degree is opposite. When the manifold pressure is high, the vacuum
degree is low. MAP sensor is also used to measure atmospheric pressure . This measurement is
completed as part of the MAP sensor calculation. When the ignition switch is turned on and the
engine is not running, the engine control module reads the intake manifold pressure as
atmospheric pressure, and adjusts the Air-Fuel ratio accordingly. With this kind of altitude
compensation, the system can maintain a low emission while maintaining maneuverability.
4. Camshaft Position Sensor (CMP)
Camshaft position sensor is a Hall-effect sensor which is installed in the vicinity of the intake
camshaft, and works together with camshaft signal wheel. The signal wheel is corresponding to
the specific engine position. ECM measures digital voltage signal through this sensor, therefore
determining the working cylinder of the engine and implementing one-to-one control. Engine
control module then calculates the actual sequence of fuel injection. If the engine is running when
the camshaft position sensor signal is lost, the fuel injection system will be converted to the
sequential fuel injection mode based on the final fuel injection pulse, while the engine continues to
run. If the engine starts after being shut down, the fuel injection sequence will be converted from
sequential injection to group injection. Even if the fault exists, the engine can be restarted.
5. Engine Coolant Temperature (ECT) Sensor
Engine coolant temperature (ECT) sensor is used to detect the engine operating temperature. ECM
provides the best control scheme depending on the temperature. The sensor uses a negative
temperature coefficient thermostat as the sensing element, when the coolant temperature rises, the
resistance decreases. At -30°C the resistance is 52,594 Ω; at 130 °C, the resistance is 77.5 Ω. The
sensors are installed in the main coolant path. The coolant temperature signal is important to the
ignition timing and fuel injection adjustment, while the signal is also transmitted to the instrument
panel (IP) and used to display the current engine working temperature.
6. Knock Sensor (KS)
Knock sensor is a frequency response sensor, installed at the engine block’s most sensitive part to
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