Aztek V6-3.4L VIN E (2001)
Powertrain Control Module: Description and Operation
Powertrain Control (PCM) Module
Powertrain Control (PCM) Module
The PCM is responsible for maintaining proper spark and fuel injection timing for all driving conditions. Ignition Control (IC) spark timing is the
method the PCM uses to control spark advance and ignition dwell. To provide optimum driveability and emissions, the PCM monitors input signals from
the following components in calculating Ignition Control (IC) spark timing:
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The Ignition Control (IC) module
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The Engine Coolant Temperature (ECT) sensor
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The Intake Air Temperature (IAT) sensor
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The Mass Air Flow (MAF) sensor
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The internal mode or Park/Neutral Position (PNP) inputs from internal mode switch or Park/Neutral position switch
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The Throttle Position (TP) sensor
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The Vehicle Speed Sensor (VSS), or Transmission Output Speed Sensor (TOSS)
The following describes the PCM to IC module circuits:
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Low resolution engine speed - PCM input - From the ignition control module, the PCM uses this signal to calculate engine RPM and crankshaft
position. The PCM also uses the pulses on this circuit to initiate injector operation.
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Low reference - PCM input - This is a ground circuit for the digital RPM counter inside the PCM, but the wire is connected to engine ground only
through the IC module. This circuit assures there is no ground drop between the PCM and IC module.
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IC timing signal - PCM output - The IC module controls spark timing while the engine is cranking. This is called bypass mode. Once the PCM
receives low resolution engine speed signals from the IC module, the PCM applies 5 volts to the IC timing signal circuit allowing the IC module to
switch spark control to PCM control.
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IC timing control - PCM output - The IC output circuitry of the PCM sends out timing signals to the IC module on this circuit. When in the Bypass
Mode, the IC module grounds these signals. When in the IC Mode, the signals are sent to the IC module to control coil dwell and spark timing.
Proper sequencing of the ignition coils is always controlled by the IC module.
