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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1977 (Engine Controls And Fuel - 3.6L (Ly7) - Troubleshooting & Diagnosis) >> Electronic Ignition System Diagnosis >> Circuit/System Testing

Circuit/System Testing

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.
  1. Turn OFF the ignition.
    2. IMPORTANT: This engine application uses 2 fuses, one for each bank, to supply ignition 1 voltage to the ignition module/coil assemblies and also to the fuel injectors. A good indication that a fuse is open is that all 4 misfire counters are incrementing on one side of the engine
  2. Inspect both fuse that supplies ignition voltage to the ignition module/coils.
    • If a fuse is open, test all ignition voltage circuits to the ignition module/coils or the fuel injectors on the engine bank, for a short to ground.
  3. Disconnect the ignition module/coil, and the fuel injector electrical connectors, for the engine bank that has the open fuse.
  4. Replace the open fuse with a new fuse.
  5. Ignition ON, engine OFF.
  6. Reconnect each ignition module/coil, and fuel injector electrical connectors, one at a time.
    • If the fuse opens when connecting an ignition module/coil or fuel injector electrical connector, then replace the component that caused the fuse to open.
  7. Ignition OFF, disconnect the appropriate ignition module/coil electrical connector.
  8. Ignition ON, verify that a test lamp illuminates between the ignition voltage circuit terminal D and ground.
    • If the test lamp does not illuminate test the ignition voltage circuit for an open/high resistance.
  9. Verify that a test lamp illuminates between the ignition module/coil ground circuit terminal A and B+.
    • If the test lamp does not illuminate, test the ignition module/coil ground circuit for an open/high resistance.
  10. Exchange the misfiring cylinder, ignition module/coil assembly with the ignition module/coil assembly from a non-misfiring cylinder.
    11. IMPORTANT: An open/high resistance on the low reference circuit to the IC module may cause a misfire.
  11. Start and idle the engine. Observe the misfire counters on the scan tool.
    • If the misfire transfers with the suspect ignition module/coil, then replace the ignition module/coil assembly.
    • If the misfire does not transfer with the suspect ignition module/coil, then measure the resistance of the IC circuit. The IC circuit should measure less than 5 ohms. If the circuit tests normal, replace the ECM.
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