OPERATION
18 Operation TP-6901 3/16a
Engine Control Module (ECM)
Figure4-9
The ECM is a digital controller that oversees the
various operating parameters of the engine. The ECM
receives input data from sensors mounted to the
engine and fuel system, and then outputs various
signals to adjust engine operation.
The ECM also performs diagnostic functions on the
fuel system. If a malfunction occurs, the ECM sends a
fault signal to alert the operator to the problem. A
corresponding Diagnostic Trouble Code (DTC) is
generated and stored in memory within the ECM. A
technician can then use a computerized diagnostic
scan tool to retrieve the stored DTC number(s) and
identify the problem.
Sensors
Heated Exhaust Gas Oxygen (HEGO) Sensor
The Heated Exhaust Gas Oxygen (HEGO) sensor
measures the amount of oxygen present in the exhaust
stream to determine whether the air-fuel ratio is too rich
or too lean.
Air Temperature / Manifold Absolute Pressure
(TMAP) Sensor
The Air Temperature / Manifold Absolute Pressure
(TMAP) sensor monitors the absolute pressure in the
intake manifold. This sensor also measures the
temperature of the incoming air. Data returned by the
TMAP sensor prompts the ECM to adjust the air-fuel
mixture as needed.
Crankshaft Position Sensor
Crankshaft Position Sensor (CPS) measures the rotary
speed and crankshaft turning angle. The ECM ensures
the ignition timing for each cylinder depending on the
turning signal. The sensor, which consists of a
permanent magnet and coil, is installed on the timing
gear cover next to the crankshaft pulley. When the
crankshaft is turning, the gear ring passes the sensor
at different speeds and causes a change of magnet
resistance at the sensor to produce a changeable
signal.
Throttle Position Sensor (TPS)
The electronic throttle control device incorporates an
internal Throttle Position Sensor (TPS), which provides
output signals to the ECM as to the location of the
throttle shaft and blade. The ECM will use the signal to
monitor and adjust the engine speed.
Engine Coolant Temperature Sensor
The engine coolant temperature sensor provides
engine coolant temperature data to the ECM. The ECM
uses this data to adjust for cold starting conditions, and
regulates various fuel and emission control functions.
Engine Oil Pressure Sender
The engine oil pressure sender ensures sufficient
lubrication throughout the engine. The sender is a
pressure valve that is monitored by the ECM. A drop in
pressure will trigger a fault code.
Figure4-10
Up-Stream Throttle Manifold Air Pressure (MAP)
Sensor (KG2204T)
The Up-stream Thr ottle Manifold Air Pressure sensor
monitors the absolute pressure in the air induction
system up-stream of the throttle. Data returned by the
MAP sensor prompts the ECM to adjust the air-fuel
mixture as needed.
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