S&T Series Blazer, Bravada, Envoy, Jimmy, Rainier, Trailblazer, Xtreme

Ignition Control Module (ICM)

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Description & Operation



Each ignition control module (ICM) has the following circuits:



An ignition 1 voltage circuit
 
A chassis ground
 
An ignition control circuit for each cylinder
 
A low reference circuit
 

The PCM controls spark by pulsing the ignition control circuits to the ICM to trigger the coils and fire the spark plugs. The PCM and ICM are internally protected against shorts to power and ground on the ignition control circuits.

The spark plugs are connected to each coil by a short boot. The boot contains a spring that conducts the spark energy from the coil to the spark plug. The spark plugs are tipped with platinum for long wear and higher efficiency.

Removal & Installation



2.2L (L61) Engine
  1. Turn OFF the ignition.
  2.  
  3. Remove the accelerator cable from the bracket.
  4.  
  5. Remove the accelerator cable bracket bolt.
  6.  
  7. Remove the accelerator cable bracket.
  8.  
  9. Disconnect the ignition control module (ICM) harness connector.
  10.  
  11. Remove the ICM retaining screws.
  12.  
  13. Remove the ICM from the ignition coil housing.
  14.  

To install:

  1. Install the ignition control module in the ignition coil housing.
  2.  
  3. Install the ICM retaining screws. Tighten the retaining screws.
  4.  
  5. Connect the ICM harness connector.
  6.  
  7. Install the accelerator cable bracket.
  8.  
  9. Install the accelerator cable bracket bolt. Tighten the retaining screws.
  10.  
  11. Install the accelerator cable to the bracket.
  12.  

2.2L (Ln2) Engine
  1. Remove the air cleaner outlet from the air cleaner.
  2.  
  3. Remove the ICM electrical connectors (1) and spark plug wires (2).
  4.  
  5. Remove the ignition coils bolts (3).
  6.  
  7. Remove the ignition coils and ICM assembly.
  8.  
  9. Installation is the reverse of the removal procedure.
  10.  

2.4L Engine
  1. Disconnect the negative battery cable.
  2.  
  3. Remove the accelerator cable from the hold down clip.
  4.  
  5. Remove the cruise control cable, if applicable.
  6.  
  7. Remove the bolt from the fuel line retaining clip.
  8.  
  9. Disconnect the 11-pin harness connector for the ignition control module (ICM).
  10.  
  11. Remove the bolts from the ignition coil and the ICM assembly-to-camshaft housing.
  12.  
  13. Remove the ignition coil and ICM assembly from the engine.
  14.  
  15. Remove the screws that retain the housing to the cover.
  16.  
  17. Disconnect the coil harness connector from the ICM.
    CAUTION
     When removing the housing from the cover, make sure the ground strap stays in place.

  18.  
  19. Remove the housing from the cover.
  20.  
  21. Remove the screws that retain the ICM to the cover.
  22.  
  23. Remove the ICM from the cover.

    Click image to see an enlarged view

    Fig. Removing the ICM from the camshaft cover

  24.  

To install:


CAUTION
DO NOT wipe grease from the module or coil if the same module is to be replaced. If a new module is to be installed, a package of silicone grease will be included with the module. Spread the grease on the metal face of the module and on the cover where the module seats. This grease is necessary for module cooling.

  1. Install the ICM to the cover.
  2.  
  3. Install the screws that retain the ICM to the cover.
  4.  
  5. Install the ground strap, if necessary.
  6.  
  7. Connect the ignition coils connector to the ICM.
    CAUTION
     When installing the housing to the cover, make sure the ground strap stays in place.

  8.  
  9. Install the housing to the cover.
  10.  
  11. Install the screws that retain the housing to the cover.
  12.  
  13. Install the spark plug boots and the retainers to the housing, if necessary.
  14.  
  15. Install the ICM assembly to the engine while carefully aligning the spark boots to the spark plug terminals.
    CAUTION
     The ICM cover bolts must be installed using isolator washers with the rubber side facing down.

  16.  
  17. Install the bolts that retain the ICM assembly to the camshaft housing after coating the bolt threads with LOCTITE, or equivalent. Tighten the bolts to 16 ft. lbs. (22 Nm).
  18.  
  19. Connect the ICM 11 pin harness connector.
  20.  
  21. Install the bolt to the fuel line retainer clip.
  22.  
  23. Install the accelerator cable into the hold down clip.
  24.  
  25. Install the cruise control cable, if applicable. Connect the negative battery cable.
  26.  

 
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