Ascender 4WD V8-5.3L (2004)
Engine Control Module: Description and Operation
Powertrain Control Module (PCM)
The PCM controls all ignition system functions, and constantly corrects the basic spark timing. The PCM monitors information from various sensor
inputs that include the following:
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The throttle position (TP) sensor
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The engine coolant temperature (ECT) sensor
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The mass airflow (MAF) sensor
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The intake air temperature (IAT) sensor
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The vehicle speed sensor (VSS)
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The transmission gear position or range information sensors
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The engine knock sensors (KS)
Modes of Operation
There is one normal mode of operation, with the spark under PCM control. If the CKP pulses are lost the engine will not run. The loss of a CMP signal
may result in a longer crank time since the PCM cannot determine which stroke the pistons are on. Diagnostic trouble codes are available to accurately
diagnose the ignition system with a scan tool.