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Circuit/System Testing

WARNING: This page is about a different car, the 2012 Buick Verano. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, disconnect the X3 harness connector at X50A fuse block-underhood.
  2. Remove the control circuit terminal 34 using terminal release tool J-44020-4, connect the X3 harness connector to the X50 fuse block underhood.
  3. Connect a test lamp between the control circuit terminal 34 and B+, engine running.
  4. Verify the test lamp turns ON and OFF when commanding the Q2 A/C compressor clutch ON and OFF with a scan tool.
    • If the test lamp is always OFF 
    1. Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON.
    2. 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
    3. Ignition OFF
    4. 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, replace the K20 ECM.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the 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, replace the K20 Engine Control Module.
    • If the test lamp turns ON and OFF 
  5. Ignition OFF and all vehicle systems OFF, connect the harness connector at the X50A fuse block-underhood, disconnect the harness connector at the Q2 A/C compressor clutch. It may take up to 2 minutes for all vehicle systems to power down.
  6. Test for less than 10 Ω between the Q2 A/C compressor clutch ground terminal 1 and ground.
    • If 10 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.
    • If less than 10 Ω 
  7. Connect a test lamp between the control circuit terminal 2 and ground.
  8. Verify the test lamp turns ON and OFF when commanding the Q2 A/C compressor clutch ON and OFF with a scan tool.
    • If the test lamp is always OFF and the circuit fuse is good 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A fuse block-underhood.
    2. 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, replace the X50A fuse block-underhood.
    • If the test lamp is always OFF and the circuit fuse is open 
    1. Ignition OFF
    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, replace the Q2 A/C compressor clutch.
    • If the test lamp is always ON 
    1. Ignition OFF, disconnect the X1 harness connector at the X50A fuse block-underhood, Ignition ON.
    2. Test for less then 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 X50A fuse block-underhood.
    • If the test lamp turns ON and OFF 
  9. Replace the Q2 A/C compressor clutch.
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