Ignition Control Module (Icm); Ignition Control Pcm Output; Powertrain Control Module (Pcm) - Isuzu 1999 RODEO Workshop Manual

6E1–436 RODEO X22SE 2.2L ENGINE DRIVEABILITY AND EMISSION
f Engine coolant temperature (ECT) sensor.
f Throttle position (TP) sensor.
f Vehicle speed (vehicle speed sensor).
f PCM and ignition system supply voltage.

Ignition Control Module (ICM)

The powertrain control module (PCM) controls engine
ignition through a solid–state switching unit called the
ignition control module (ICM). The software in the PCM
uses input from several sensors to determine the timing,
duration, and strength of the spark.
f The crankshaft position (CKP) sensor sends the PCM
a 58X signal related to the exact position of the
crankshaft.
f The camshaft position (CMP) sensor sends a signal
related to the position of the camshaft.
Based on these sensor signals, as well as engine load
and engine coolant temperature information, the PCM
controls the switching function of the ICM by sending it a
5V signal. As long as the ICM receives the signal, it allows
battery voltage to the ignition coil. That voltage allows a
magnetic field to build in the coil.
When the PCM requires a spark plug to fire, it shuts off the
5V signal to the ICM grounding it internally. This triggers
the ICM to switch off the battery voltage to the ignition coil,
which causes the field to collapse. The lines of magnetic
force pass through the secondary portion of the coil as
they collapse. As they intersect the coil, they induce high
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voltage in the secondary ignition circuit which travels
toward ground through the spark plug.

Ignition Control PCM Output

The PCM provides a zero volt (actually about 100 mV to
200 mV) or a 5–volt output signal to the ignition control
(IC) module. When the ignition control (IC) module
receives the 5–volt signal from the PCM, it provides a
ground path for the B+ supply to the primary side of the
coil and creates a magnetic field in the coil. When the
PCM shuts off the 5–volt signal to the ignition control
module, the ground path for the primary coil is broken.
The magnetic field collapses and induces a high voltage
secondary impulse which fires the spark plug and ignites
the air/fuel mixture.

Powertrain Control Module (PCM)

The PCM is responsible for maintaining proper spark and
fuel injection timing for all driving conditions. To provide
optimum driveability and emissions, the PCM monitors
the input signals from the following components in order
to calculate spark timing:
f Engine coolant temperature (ECT) sensor.
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f Intake air temperature (IAT) sensor.
f Throttle position (TP) sensor.
f Vehicle speed sensor (VSS).
f Crankshaft position (CKP) sensor.
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