Aurora V6-214 3.5L VIN H SFI (2001)
Powertrain Control Module: Description and Operation
Preliminary Information
The PCM is responsible for maintaining the 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 to calculate Ignition Control (IC) spark timing:
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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 inputs from transaxle range switch
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The Throttle Position (TP) sensor
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The Vehicle Speed Sensor (VSS)
Powertrain
The powertrain used in this vehicle consists of a twin cam V6 engine mated to a 4T65-E electronically controlled transaxle. The powertrain has
electronic controls to reduce exhaust emissions while maintaining excellent driveability and fuel economy. The Powertrain Control Module (PCM) is the
heart of this control system.
The powertrain control module is designed to maintain exhaust emission levels to Federal or California standards while providing excellent driveability
and fuel efficiency. Review the components and the wiring diagrams in order to determine which systems are controlled by the PCM. The PCM monitors
numerous engine and vehicle functions. The following are some of the functions that the PCM controls:
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The engine fueling
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The Ignition Control (IC)
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The Knock Sensor (KS) system
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The Evaporative Emissions (EVAP) system
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The Secondary Air Injection (AIR) system, if equipped
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The Exhaust Gas Recirculation (EGR) system
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The automatic transmission functions
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The generator
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The A/C clutch control
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The cooling fan control
Powertrain Control Module Function
The PCM constantly looks at the information from various sensors and other inputs, and controls systems that affect the vehicle performance and
emissions. The PCM also performs diagnostic tests on various parts of the system. The PCM can recognize operational problems and alert the driver via
the Malfunction Indicator Lamp (MIL). When the PCM detects a malfunction, the module stores a Diagnostic Trouble Code (DTC). The problem area
is identified by the particular DTC that is set. The module supplies a buffered voltage to various sensors and switches. The input and output devices in
the control module include analog to digital converters, signal buffers, counters, and output drivers. The output drivers are electronic switches which
complete a ground circuit when turned on. Most PCM controlled components are operated via output drivers. The PCM monitors these driver circuits for
proper operation, and in most cases can set a DTC corresponding to the controlled device if a problem is detected.
Torque Management
The torque management is a function of the PCM that reduces engine power under certain conditions.
Torque management is performed for 3 reasons:
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To prevent any overstress of the powertrain components
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To limit the engine power when the brakes are applied
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To prevent any damage to the vehicle during certain abusive maneuvers.
The PCM uses the following data to calculate engine output torque:
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The manifold vacuum
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The intake air temperature
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The spark retard
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The engine speed
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The engine coolant temperature
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The A/C clutch status
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The EGR valve position
The PCM then looks at the torque converter status, the transaxle gear ratio, and the brake switch inputs and determines if any torque reduction is
required. If a torque reduction is required, the PCM retards the spark as appropriate to reduce the engine torque output. In the case of abusive maneuvers,
the PCM may also shut off the fuel to certain cylinders to reduce the engine power.
The following are 4 instances when engine power reduction is likely to be experienced
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During transaxle upshifts and downshifts