GM Malibu/Cutlass 1997-2000

Powertrain Control Module (PCM)

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OPERATION





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Fig. The PCM is the control center of the fuel injection and electronic ignition systems

The Powertrain Control Module (PCM) performs many functions on your vehicle. The module accepts information from various engine sensors and computes the required fuel flow rate necessary to maintain the correct amount of air/fuel ratio throughout the entire engine operational range.

The PCM controls the following items:



Fuel metering system
 
Transaxle shifting
 
Ignition timing
 
On Board Diagnostics for powertrain functions
 

The PCM constantly looks at the information from various sensors, and controls the systems that affect vehicle performance. The PCM also performs the diagnostic function of the system. It can recognize operational problems, alert the driver through the Malfunction Indicator Light (MIL) or SERVICE ENGINE SOON light, and store diagnostic trouble codes which identify the problem areas to aid in making repairs.

The PCM supplies either 5.0 or 12.0 volts to power various sensors or switches. This is done through resistances in the PCM which are so high in value that even a test light will not light when connected to the circuit. In some cases, even an ordinary DMM will not give an accurate reading because it's resistance is too low. A DMM with at least 10 megaohms input impedance is required to ensure accurate voltage readings.

The PCM controls output circuit devices such as fuel injectors, idle air control, cooling fan relays, etc. by controlling the ground or power feed circuit through transistors or a device called a "Driver".

REMOVAL & INSTALLATION




WARNING
In order to prevent internal damage to the PCM, the ignition must be OFF and the battery DISCONNECTED when disconnecting or connecting power to the PCM or it's circuits. The ignition switch should be OFF for at least 10 seconds before disconnecting power to the PCM so that the IAC valve has time to move to the ENGINE OFF position.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the left sound insulator below the steering wheel.
  4.  



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Fig. The insulator below the steering column covers the PCM

  1. Loosen the 2 PCM electrical connector's screws.
  2.  



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Fig. Loosen the screws that secure the PCM electrical connectors



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Fig. View of the PCM connectors (1) and the Data Link Connector (2)


WARNING
Do not touch the PCM connector pins or soldered components on the circuit board in order to prevent possible Electrostatic Discharge (ESD) damage. Do not remove the integrated circuit boards from the carrier.

  1. Detach the PCM electrical connectors and move them out of the way.
  2.  
  3. Open the PCM bracket latch.
  4.  



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Fig. Move the PCM electrical connectors out of the way, open the PCM bracket latches and firmly pull down the PCM

  1. Remove the PCM from the bracket.
  2.  

To install:


NOTE
If installing a new PCM, make sure to match the service coding information on the label.



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Fig. When installing a new PCM, always make sure to match the service coding information on the label

  1. Slide the PCM into the PCM bracket until retainer locks the PCM into position.
  2.  



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Fig. View of the PCM bracket latch

  1. Close the PCM bracket latch.
  2.  
  3. Attach the PCM electrical connectors.
  4.  
  5. Tighten the connector screws to 71 inch lbs. (8 Nm).
  6.  
  7. Install the sound insulator.
  8.  
  9. Connect the negative battery cable.
  10.  

 
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