GM Storm/Spectrum 1985-1993 Repair Guide

Engine Control Module

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REMOVAL & INSTALLATION




CAUTION
To prevent the possibility of permanent ECM damage, the ignition switch must always be OFF when disconnecting power from or reconnecting power to the ECM. This includes unplugging the ECM connector, disconnecting the negative battery cable, removing the ECM fuse or even attempting to jump your dead battery using jumper cables.

Spectrum

See Figures 1 and 2

The ECM is located in the passenger compartment, above the passenger kick pad. The ECM used in the Spectrum contains a Programmable Read Only Memory (PROM) chip which contains data relevant to the specific vehicle model. If the ECM is replaced, the PROM must be switched to the new ECM.

  1. Make sure the ignition is OFF , then disconnect the negative battery cable.
  2.  
  3. Unplug the wiring harness connectors from the ECM.
  4.  
  5. Remove the ECM mounting hardware, then remove the ECM from the passenger compartment.
  6.  
  7. If the ECM is being replaced, remove the PROM access cover, then use a PROM extraction tool to carefully remove the PROM chip from the old ECM:
    1. Starting at the opposite end from the reference mark, gently work the extraction tool tan under the PROM using a slight rocking motion.
    2.  
    3. Go to the reference end of the PROM and push the tang under the PROM with your thumb pressing on the tool as close to the tang end as possible.
    4.  
    5. Make sure the tang end is completely under the PROM, but above the mating socket, then grasp the PROM firmly between your thumb and forefinger while pulling upward and remove the PROM from the mating socket.
    6.  
    7. Position the PROM on a clean flat surface with the leads pointing downward, then carefully press the PROM inserting tool firmly over the PROM. Make sure the reference end can be seen at the tool cut out end.
    8.  
    9. Compare the service number on the new ECM to the old ECM to double check it is the correct model, then remove the PROM access cover.
    10.  

  8.  


WARNING
Any time the PROM is installed backwards and the ignition switch is turned ON, the PROM is destroyed.

    1. Using the insertion tool, mate the PROM to the circuit board. Make sure the reference ends of both the RPOM and socket are aligned in the same direction. The PROM chip will not be fully seated at this point.
    2.  
    3. Turn the insertion tool over and using the blunt end, press the PROM down until fully seated. Check that the PROM pins are properly seated in the socket and that the PROM and socket ends are properly aligned.
    4.  
    5. Install the access cover.
    6.  


  1. To install, reverse Steps 1-3.
  2.  
  3. Turn the ignition ON and activate the self-diagnostics to check for proper ECM operation. Refer to the procedure later in this section.
  4.  



Click image to see an enlarged view

Fig. Fig. 1: Remove the access cover from the ECM in order to remove the PROM chip - Spectrum



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Fig. Fig. 2: The proper installation and removal tools are essential when servicing the ECM PROM - Spectrum

Storm

See Figure 3

The ECM is located under the instrument panel, left of the steering column. Unlike the model used in the Spectrum, the Geo Storm's ECM does not have any serviceable components. Data relevant to the vehicle model (which is necessary for proper ECM operation) is programmed into the ECM's Electronically Erasable Programmable Read Only Memory (EEPROM). If the ECM is replaced, the TECH1® or an equivalent scan tool must be used to program the EEPROM in the new ECM. If a proper tool is not available, the vehicle should be taken to a reputable repair shop that has the proper equipment.

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the lower trim panel or sound insulator, as necessary for access.
  4.  
  5. Remove the two 10mm nuts securing the ECM.
  6.  
  7. Unplug the wiring harness connectors from the ECM.
  8.  


WARNING
To prevent the possibility of electrostatic discharge damage to the ECM, DO NOT touch the connector pins or soldered components on the circuit board.

  1. Reverse the removal procedure to install.
  2.  
  3. If installing a new ECM, use the TECH1® or an equivalent scan tool to program the EEPROM. Be sure to follow all of the tool manufacturer's instructions.
  4.  



Click image to see an enlarged view

Fig. Fig. 3: ECM location - Storm

 
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