Tracker 4WD V6-2.5L VIN 4 (2001)
Ignition Coil: Description and Operation
Operation
Ignition System
The PCM uses reference pulses from the Camshaft Position (CMP) sensor in order to determine engine speed. The PCM cannot operate the ignition
system- or the fuel injectors-without the engine speed signal from the CMP.
The six ignition coils supply spark to each engine cylinder, or spark plug, at precisely the right time. When the PCM sends a signal to the ignition
module that is built into the ignition coil, the module responds by interrupting the current flow in the primary coil windings. Interrupting the current flow
causes the electrical field around the primary coil to collapse, inducing a high voltage in the secondary coil. The secondary coil voltage travels
unhindered to the spark plug, through the high voltage output terminal and boot assembly.
The PCM also uses the CMP sensor signal as an input for control of the fuel injectors and ignition timing. The Crankshaft Position (CKP) sensor signal
is used by the PCM for engine misfire detection.
The PCM provides three modes of ignition timing control. Each ignition timing mode provides the most suitable spark advance for optimal engine
performance. The following are the 3 modes of ignition timing control:
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The initial timing control ignition advance provides better starting performance of the engine at start-up, when engine speed is less than 500 RPM.
The PCM sets initial ignition timing advance to 5 degrees Before Top Dead Center (BTDC).
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Basic timing control-After the engine is running, ignition timing advance is determined by combining basic timing control and compensating
timing control. Basic timing control ignition advance is based on engine coolant temperature, engine speed, and intake air volume. The ignition
timing advance value, calculated from the Engine Coolant Temperature (ECT) sensor, the CMP sensor, and the Mass Air Flow (MAF) sensor
input, is added to the 5 degrees initial advance, and modified by the compensating timing control value.
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The compensating timing control ignition advance is added to the basic timing control value. The following are the most important factors in
calculating the compensating ignition advance value:
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Engine coolant temperature
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Intake air temperature
