Montana, Silhouette, Venture 2000-2005

Diagnosis & Testing

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There are 3 dual-tower ignition coils that are part of the ignition control module (ICM). The ICM contains coil driver circuits that command the coils to operate. The Powertrain Control Module (PCM) controls each dual-tower ignition coil by transmitting timing pulses on the ignition coil control circuit to the ICM for the proper coil to enable a spark event.

  1. Inspect the spark plug wires for proper orientation.
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  3. With the ignition OFF, remove the fuel pump relay.
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  5. Crank the engine and test for a strong spark on each cylinder spark plug wire using a suitable spark plug tester. Ground the companion cylinder spark plug wire of each cylinder when it is tested.

    If a strong bright blue spark is present on all of the cylinders, remove and inspect all of the spark plugs for proper torque, proper gap, wear, damage, and fouling. Replace the spark plugs if necessary.
     
    If there is no spark on any of the cylinders, test the ignition voltage circuit of the Ignition Coil Module (ICM) for an open/high resistance or short to ground, or test the ground circuit of the ICM for an open/high resistance, or a faulty ICM. The wire circuit resistance should measure less than 3 ohms.
     
    If there is no spark on any of the cylinders, or spark is weak or intermittent, test the IC circuit for an open/high resistance, or a faulty ICM. The wire circuit resistance should measure less than 3 ohms.
     
    If spark is present on one or more of the cylinders, inspect and test the spark plug wires for arching, cuts, rubbing on other components, and proper resistance.
     
    If all tests are normal, then the system is operating correctly.
     

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  7. Test for an intermittent and/or poor connection at the PCM and ICM. It is important to test terminal contact at the component and any inline connectors before replacing a suspect component. Mating terminals must be inspected to ensure good terminal contact.
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Flat Wire (Dock & Lock) Connectors



There are no serviceable parts for flat wire (dock and lock) connectors on the harness side or the component side.

  1. Follow the procedure below in order to test terminal contact:
    1. Remove the component in question.
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    3. Visually inspect each side of the connector for signs of contamination. Avoid touching either side of the connector as oil from your skin may be a source of contamination as well.
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    5. Visually inspect the terminal bearing surfaces of the flat wire circuits for splits, cracks, or other imperfections that could cause poor terminal contact. Visually inspect the component side connector to ensure that all of the terminals are uniform and free of damage or deformation.
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    7. Insert the appropriate adapter from the on the flat wire harness connector in order to test the circuit in question.
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Testing For Proper Terminal Contact In Bussed Electrical Centers (BEC)



It is very important to use the correct test adapter when testing for proper terminal contact of fuses and relays in a bussed electrical center (BEC). Use a GM approved Terminal Test Kit (such as J-35616-35) to test for proper terminal contact. Failure to use an approved test kit can result in improper diagnosis of the BEC.

  1. Follow the procedure below in order to test terminal contact:
    1. Separate the connector halves.
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    3. Visually inspect the connector halves for contamination. Contamination may result in a white or green build-up within the connector body or between terminals. This causes high terminal resistance, intermittent contact, or an open circuit. An underhood or underbody connector that shows signs of contamination should be replaced in its entirety: terminals, seals, and connector body.
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    5. Using an equivalent male terminal from a suitable terminal repair kit, test that the retention force is significantly different between a good terminal and a suspect terminal. Replace the female terminal in question.
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