Century, Grand Prix, Impala, Intrigue, Lumina, Monte Carlo, Regal 2001-2005

Powertrain Control Module

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Operation



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 lamp (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 control module supplies a buffered voltage to various sensors and switches. Review the components and wiring diagrams in order to determine which systems are controlled by the PCM.

The following are some of the functions that the PCM monitors and controls:



The engine fueling
 
The ignition control (IC)
 
The Knock Sensor (KS) System
 
The Evaporative Emissions (EVAP) System
 
The Secondary Air Injection (AIR) System, if equipped
 
The Exhaust Gas Recirculation (EGR) System, if equipped
 
The automatic transmission functions
 
The generator
 
The A/C clutch control
 
The cooling fan control
 

Removal & Installation



Service of the Powertrain Control Module (PCM) should normally consist of either replacement of the PCM or electrically erasable programmable read only memory (EEPROM) programming. If the diagnostic procedures call for PCM replacement, inspect the PCM first to see if the replacement is the correct part. If the PCM is faulty, remove the PCM and install the new service PCM.

The new service PCM will not be programmed. You must program the new PCM. DTC P0602 indicates the EEPROM is not programmed or has malfunctioned.


NOTE
Do not touch the connector pins or soldered components on the circuit board in order to prevent possible electrostatic discharge (ESD) damage to the PCM.


NOTE
Turn the ignition OFF when installing or removing the PCM connectors and disconnecting or reconnecting the power to the PCM (battery cable, PCM pigtail, PCM fuse, jumper cables, etc.) in order to prevent internal PCM damage.


CAUTION
It is necessary to record the remaining engine oil life. If the replacement module is not programed with the remaining engine oil life, the engine oil life will default to 100%. If the replacement module is not programmed with the remaining engine oil life, the engine oil will need to be changed at 5000 km (3,000 mi) from the last engine oil change.

3.1L And 3.4L Engine
  1. Using a scan tool, retrieve the percentage of remaining engine oil. Record the remaining engine oil life.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the air cleaner housing cover assembly.
  6.  
  7. Without disconnecting the PCM connectors, remove the PCM and the harness from the air cleaner housing.
  8.  
  9. Disconnect the PCM connectors and remove the PCM from the connectors.
  10.  
  11. To install, reverse removal procedure.
  12.  
  13. The new PCM must be programmed.
  14.  

3.5L, 3.8L, 3.9L And 5.3L Engines
  1. Using a scan tool, retrieve the percentage of remaining engine oil. Record the remaining engine oil life.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Remove the air cleaner housing cover assembly.
  6.  
  7. Remove the left front inner fender brace.
  8.  
  9. Remove the air cleaner assembly.
  10.  
  11. Disconnect the ECM electrical connectors.
  12.  
  13. Remove the ECM from the air cleaner lower housing.
  14.  
  15. To install, reverse removal procedure and program the new PCM. Removing and installing PCM-3.5L and 3.9L Engines

    Click image to see an enlarged view

    Fig.



    Click image to see an enlarged view

    Fig.

  16.  

Testing



Many intermittent open or shorted circuits come and go with harness and connector movement caused by vibration, engine torque, bumps and rough pavement, etc.

  1. Test the wiring harness and connectors by performing the following:

    Move the related connectors and wiring while monitoring the appropriate scan tool data.
     
    Move the related connectors and wiring with the component commanded ON and OFF, with the scan tool. Observe the components operation.
     
    With the engine running, move the related connectors and wiring while monitoring engine operation
     
    If harness or connector movement affects the data displayed, the component and system operation, or the engine operation, inspect and repair the harness or connections as necessary
     

  2.  
  3. Test the electrical connections and/or wiring by performing the following:

    Inspect for incorrect mating of the connector halves, or terminals not fully seated in the connector body, backed-out.
     
    Inspect for improperly formed or damaged terminals. Test for incorrect terminal tension.
     
    Inspect for poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body.
     
    Inspect for corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation with little visible evidence. Look for swollen and stiff sections of wire in the suspect circuits.
     
    Inspect for wires that are broken inside the insulation.
     

  4.  

 
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