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Home >> Chevrolet >> 2018 >> Suburban 3500 HD LT >> Repair and Diagnosis >> External Pages >> Different car >> Section 9 (Engine Controls And Fuel - 5.3L (L83) Or 6.2L (L86) - DTC P0443 To DTC P3452 And Diagnostic Information And Procedures) >> Diagnostic Information And Procedures >> Electronic Ignition System Diagnosis >> Circuit/System Testing

Circuit/System Testing

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2018 GMC Yukon XL, 2018 GMC Yukon, 2018 Chevrolet Tahoe, 2018 Chevrolet Suburban, and 2018 Cadillac Escalade ESV. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: Do not perform this diagnostic procedure unless you were sent here from a misfire DTC or the Engine Cranks But Does Not Run diagnostic.
  1. 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.
  2. Test for less than 5 Ω between the ground circuit terminal 1 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 
  3. Test for less than 5 Ω between the low reference circuit terminal 2 and ground.
    • If 5 Ω or greater 
    1. Ignition OFF, disconnect the X3 harness connector at the K20 Engine Control Module.
    2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K20 Engine Control Module.
    • Go to next step: If less than 5 Ω 
  4. Ignition ON.
  5. Verify a test lamp illuminates between the ignition circuit terminal 4 and ground.
    • If the test lamp does not illuminate 
    1. Ignition OFF.
    2. 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 
  6. Ignition OFF, exchange the suspect T8 Ignition Coil with the T8 Ignition Coil of a known functioning cylinder.
  7. Engine Running.
  8. Verify the scan tool Cylinder 1 - 8 Current Misfire Counter does not increment for the same cylinder that the suspect T8 Ignition Coil was removed from.
    • If increments 

      Replace the K20 Engine Control Module.

    • Go to next step: If does not increment 
  9. Test or replace the T8 Ignition Coil.
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