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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 >> DTC P0643 >> Circuit/System Testing
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Circuit/System Testing

    NOTE:

    Additional DTCs may set when disconnecting the components.

  1. Ignition OFF, disconnect the harness connector at all appropriate sensors for DTC P0643. Refer to Diagnostic Aids.
  2. Ignition ON, test for 4.5 - 5.5 V between the 5 V reference circuit and ground.
    • If less than 4.5 V 
    1. Ignition OFF.
    2. Test for infinitive resistance between the 5 V reference circuit and ground.
      • If less than infinitive resistance, repair the short to ground in the circuit.
      • If infinitive resistance, replace the K20 Engine Control Module.
    • If greater than 5.5 V 
    1. Ignition OFF.
    2. Disconnect the harness connector at the K20 Engine Control Module.
    3. Ignition ON, test for less then 1 V between the 5 V reference and ground
      • If 1 V or greater, repair the short to voltage in the circuit.
      • If less than 1 V, replace the K20 Engine Control Module.
    • Go to next step: If between 4.5 - 5.5 V 
    3. NOTE:

    A short to voltage on the signal circuit of certain components may cause this DTC to set.

  3. Verify with a scan tool that DTC P0643 is not set while connecting each component associated with the 5 V reference circuit one at a time.
    • If DTC P0643 resets 

      Replace the component that sets the DTC

    • Go to next step: If DTC P0643 does not reset 
  4. All OK.
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