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Home >> Chevrolet >> 2017 >> City Express LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls And Fuel - 2.0L >> Diagnostic Information And Procedures >> Electronic Ignition System Diagnosis >> Circuit/System Testing

Circuit/System Testing

  1. Engine Running, perform the Cylinder Power Balance Test with a scan tool to isolate the misfiring cylinder.
  2. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate T8 Ignition Coil. It may take up to 2 min for all vehicle systems to power down.
  3. Test for less than 5 Ω between the ground circuit terminal 2 and ground.
    • If 5 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • Go to next step: If less than 5 Ω 
  4. Ignition ON.
  5. Verify a test lamp illuminates between the ignition circuit terminal 3 and ground.
    • If the test lamp does not illuminate and the circuit fuse is good 
    1. Ignition OFF.
    2. Disconnect the X50A Fuse Block Underhood harness connector.
    3. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • If the test lamp does not illuminate and the circuit fuse is open 
      NOTE:

      The ignition circuit may supply voltage to other components. Make sure to test all circuits and components for a short to ground that share the ignition circuit.

    1. Ignition OFF, remove the test lamp, and disconnect all components on the circuit.
    2. Test for infinite resistance between the ignition circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Replace the fuse, ignition ON.
    4. Verify the fuse is good after connecting each of the components one at a time.
      • If the fuse opens, replace the component that opens the fuse when connected.
      • If the fuse is good, all OK.
    • Go to next step: If the test lamp illuminates 
  6. Remove the fuel pump fuse.
  7. Connect a DMM between the T8 Ignition Coil control circuit terminal 1 and ground. Set the DMM to the DC 40 Hz scale and utilize the Min-Max function:
  8. Verify the DMM displays greater than 4 Hz while cranking the engine.
    • If less than 4 Hz 
    1. Ignition OFF, disconnect the F10 harness connector at the K20 Engine Control Module.
    2. Test for infinite resistance between the control circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
    3. Test for less than 2 Ω in the control circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω
    4. Ignition ON.
    5. Test for less than 1 V between the control circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
    • Go to next step: If greater than 4 Hz 
  9. Ignition OFF.
  10. Disconnect the harness connector at the C9 Ignition Coil Capacitor.
  11. Test for less than 5 Ω between the ground circuit terminal 2 and ground.
    • If 5 Ω or greater 
    1. Ignition OFF.
    2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
    • Go to next step: If less than 5 Ω 
  12. Ignition ON.
  13. Verify a test lamp illuminates between the ignition circuit terminal 1 and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF.
    2. Disconnect the X50A Fuse Block Underhood harness connector.
    3. Test for less than 2 Ω in the ignition circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
    • Go to next step: If the test lamp illuminates 
  14. Test for infinite resistance from ignition terminal 1 and ground terminal 2.
    • If not infinite resistance 
    • Replace the condenser.
    • Go to next step: If infinite resistance 
  15. Ignition OFF, exchange the suspect T8 Ignition Coil with the T8 Ignition Coil of a known functioning cylinder, engine Running.
  16. Verify the same cylinder that the suspect T8 Ignition Coil was removed from is functioning normally.
    • If not functioning normally 

      Replace the K20 Engine Control Module.

    • Go to next step: If functioning normally 
  17. Test or replace the suspect T8 Ignition Coil.
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