Ignition System; Map And Tmap Sensors - Kohler KG2204 Service

1.11. Ignition System

Figure 1-13 Ignition Coil
The ignition system is a wasted spark system. In a
wasted spark system, spark is provided to two
cylinders simultaneously. One spark plug fires during
the compression stroke of a cylinder and creates
combustion; while the other spark plug fires during the
exhaust stroke and is wasted.
After receiving the crank signal, the ECM sends the
ignition control module a triggering signal that tells the
ignition module exactly when to make the ignition coil
spark. The ignition coil then sends a spark to each
engine cylinder through a high tension lead and the
spark plugs.
TP-6903 5/16a

1.12. MAP and TMAP Sensors

1.12.1. Manifold Air Temperature and
Manifold Absolute Pressure
(TMAP) Sensor
1. TMAP sensor
2. Wire harness connector
Figure 1-14 TMAP Sensor
The TMAP sensor is a combination of two sensors: the
manifold absolute pressure (MAP) sensor and the
manifold air temperature (MAT) or intake air
temperature (IAT) sensor. The MAP Sensor measures
the intake manifold pressure and the MAT or IAT
sensor measures the air temperature in the intake
manifold. The ECM uses the pressure and temperature
readings in conjunction with other inputs to estimate
the airflow requirement of the engine.
The MAT sensor uses a variable resistance thermistor
to measure the air temperature and then sends a
voltage signal to the ECM. The ECM interprets the
signal voltage to indicate the temperature. If a cold start
is indicated, the ECM enriches the fuel mixture.
The MAP (Manifold Absolute Pressure) sensor portion
of the TMAP sensor is a pressure transducer
connected to the intake manifold. The MAP Sensor
uses a variable resistor to measure the absolute
pressure in the intake manifold. The ECM uses the
signal from the MAP sensor to determine the engine
load and then adjusts the fuel mixture to improve
performance and emissions.
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Fuel System Overview 17