Powertrain Control Module

On Century and Grand Prix, PCM is located left side of engine compartment, inside air cleaner assembly. On Malibu, PCM is located under Instrument Panel (I/P), next to Data Link Connector (DLC). See Fig 1 and Fig 2 .

The powertrain has electronic controls to reduce exhaust emissions while maintaining excellent driveability and fuel economy. The Powertrain Control Module (PCM) is the control center of this system. The PCM monitors numerous engine and vehicle functions. The PCM constantly looks at the information from various sensors and other inputs, and controls the systems that affect vehicle performance and emissions. The PCM also performs the diagnostic tests on various parts of the system. The PCM can recognize operational problems and alert the driver via the Malfunction Indicator Light (MIL). When the PCM detects a malfunction, the PCM stores a Diagnostic Trouble Code (DTC). The problem area is identified by the particular DTC that is set. The PCM supplies a buffered voltage to various sensors and switches. Review the components and wiring diagrams to determine which systems are controlled by the PCM. The following are some of the functions that the PCM controls:

• The engine fueling.
• The Ignition Control (IC).
• Transmission shifting.
• The Knock Sensor (KS) system.
• The Evaporative Emissions (EVAP) system.
• The Secondary Air Injection (AIR) system (if equipped).
• The Exhaust Gas Recirculation (EGR) system.
• The automatic transmission functions.
• The generator.
• The A/C clutch control.
• The cooling fan control.

The PCM constantly looks at the information from various sensors and other inputs and controls systems that affect 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 MIL. When the PCM detects a malfunction, the PCM stores a DTC. The problem area is identified by the particular DTC that is set. The PCM supplies a buffered voltage to various sensors and switches. The input and output devices in the PCM include analog-to-digital converters, signal buffers, counters, and output drivers. The output drivers are electronic switches that complete a ground or voltage 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.

Fig 1: Locating PCM (Century & Grand Prix)

Courtesy of GENERAL MOTORS CORP.