GM Cadillac Deville_Fleetwood_ELD_Seville 1990-1998

Powertrain Control Module (PCM)

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The PCM constantly monitors the input information, processes this information from various sensors, and generates output commands to the various systems that affect vehicle performance.

The PCM monitors engine operations and environmental conditions (ambient temperature, barometric pressure, etc.) needed to calculate the fuel delivery time (pulse width/injector on-time) of the fuel injector. The fuel pulse may be modified by the PCM to account for special operating conditions, such as cranking, cold starting, altitude, acceleration, and deceleration.

The ability of the PCM to recognize and adjust for vehicle variations (engine transmission, vehicle weight, axle ratio, etc.) is provided by a removable calibration unit , referred to as a PROM (Programmable Read Only Memory) that is programmed to tailor the PCM for the particular vehicle. There is a specific PCM/PROM combination for each specific vehicle, and the combinations are not interchangeable with those of other vehicles.

The PCM also performs the diagnostic function of the system. It can recognize operational problems, alert the driver through the SERVICE ENGINE SOON light, and store a code or codes, which identify the problem areas to aid the technician in making repairs.

OPERATION



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.

Based on the information that is received and programmed into the PCM's memory, the PCM generates output signals to control relays, actuators and solenoids. The PCM also sends out a command to the fuel injectors that meters the appropriate quantity of fuel. The module automatically senses and compensates for any changes in altitude when driving your vehicle.

REMOVAL & INSTALLATION



Later Model Vehicles

This powertrain has very complex components with equally complex operating characteristics. Therefore, it is essential that the Powertrain diagnostic procedures given be used for diagnosis before any repairs are made. While the PCM may appear to be the source of a problem, it may be operating properly based on the incorrect inputs it receives.


NOTE
To prevent internal PCM damage, the ignition must be in the OFF (Lock) position when disconnecting or reconnecting power to the PCM, as when the battery cables, PCM connectors, or fuses are connected or disconnected. The ignition switch supplies power to the PCM in all key positions except LOCK. The key must be in the LOCK position for a minimum of 30 seconds prior to disconnecting power to the PCM. This is to allow the PCM to store the Transaxle fluid life, transaxle shift adapts and Throttle Position Learned value into the EEPROM.

Service of the PCM will consist of replacement of the PCM and flashing the EPROM. When flashing the EPROM, also refer to the latest service publications for updated programming procedures and information.

The service PCM will not contain data. The EPROM must be flashed after the service PCM is installed.

  1. Record the Transaxle Fluid and Engine Oil Life Indexes.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Detach the IAT sensor connector.
  6.  
  7. Remove the gusset (brace) from between the LH fender and t he radiator core support by removing the 5 attaching bolts.
  8.  
  9. Loosen the Intake Air duct clamp at the MAF sensor.
  10.  
  11. Remove the Intake Air duct/air cleaner assembly.
  12.  
  13. Remove the air cleaner assembly.
  14.  
  15. Lift the air inlet assembly onto the radiator core support area by pulling firmly straight up.
  16.  
  17. Open the air inlet housing to gain aces to the PCM.
  18.  
  19. Loosen the connector attaching bolts.
  20.  
  21. Detach both PCM connectors.
  22.  

To install:



If installing a replacement PCM the KS module will have to be transferred from the original PCM to the replacement PCM.
 
If installing a replacement, the PCM isolators will have to be transferred to the replacement PCM.
 

  1. Slide the PCM isolators on to the PCM.
  2.  
  3. Install the PCM connectors and tighten the screws to 71 inch lbs. (8 Nm).
  4.  
  5. Close and latch the air inlet housing.
  6.  
  7. Install the air inlet housing by inserting the outboard locating pin into the inside fender alignment hole.
  8.  
  9. Press the air inlet housing firmly down to engage the bottom locating pins.
  10.  
  11. Ensure that the locating pin grommets are present and properly positioned in the bottom of the air cleaner assembly.
  12.  
  13. Install the intake air duct/air cleaner assembly onto the air inlet housing.
  14.  
  15. Install the intake air duct to the MAF sensor and tighten the clamp.
  16.  
  17. Attach the IAT sensor connector.
  18.  
  19. Install the gusset (brace) between the LH fender and the radiator core support. Tighten the attaching bolts to 18 ft. lbs. (24 Nm).
  20.  
  21. Disconnect the negative battery cable.
  22.  

Early Model Vehicles
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the glove box assembly, if necessary. Remove the right lower dash panel and kick panel to gain access to the PCM.
  4.  
  5. Detach the connectors from the PCM.
  6.  
  7. Remove the PCM mounting hardware and remove the PCM from the passenger compartment.
  8.  
  9. Remove the PROM access cover from the old PCM. Using 2 fingers, push both retaining tabs back away from the PROM at the same time. Grasp the PROM at both ends and lift the up out of the PROM socket.
  10.  

To install:

  1. Install the old PROM into the socket of the PCM. The small notches in the PROM must align with the small notches in the socket on the PCM. Press on the ends of the PROM unit until the retaining clips snap into the ends of the PROM. Press the clips into the sides of the PROM until they snap into place. Do not press on the middle of the PROM; only on the ends.
  2.  
  3. Install the PROM accessories cover.
  4.  
  5. Install the PCM and mounting hardware into the passenger compartment of the vehicle. Secure the PCM in place.
  6.  
  7. Reattach the harness connectors at the PCM.
  8.  
  9. Install the kick panel and glove box, as required.
  10.  
  11. Reconnect the negative battery cable.
  12.  



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Fig. PCM location as seen on 1993 Eldorado and Seville



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Fig. Removing the PROM from the PCM



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Fig. Correct PROM alignment is required to complete installation into PCM

 
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