Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2002 Isuzu Rodeo S 2WD L4-2.2LFACTORY OEM SERVICE PROCEDURE
Ignition Control Module: Description and Operation
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.
- The crankshaft position (CKP) sensor sends the PCM a 58X signal related to the exact position of the crankshaft.
- 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 voltage in the secondary ignition circuit which travels toward ground through the spark plug.
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.
- The crankshaft position (CKP) sensor sends the PCM a 58X signal related to the exact position of the crankshaft.
- 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 voltage in the secondary ignition circuit which travels toward ground through the spark plug.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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