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Home › Chevrolet › 2017 › Sonic Premier, 4D Hatchback, Automatic Trans › Repair and Diagnosis › Body & Frame › Windows › Fixed And MOVEABLE Window System › Diagnostic Information and Procedures › Rear Window Defogger Malfunction › Circuit/System Testing

Circuit/System Testing

    NOTE:

    It may take up to 2 min for all vehicle systems to power down before an accurate ground or low reference circuit continuity test can be performed.

  1. Ignition/Vehicle & All vehicle systems - Off
  2. Remove the component: KR5 Rear Defogger Relay
  3. Test for less than 10 ohms between the test points: Ground circuit terminal 85 and Ground
    • If 10 ohms or greater 
    1. Ground Connection - Disconnect
    2. Test for less than 2 ohms between the test points: Ground circuit terminal 85 and Ground Connection
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Repair the open/high resistance in the ground connection.
    • If less than 10 ohms  : Go to next step.
  4. Connect a test lamp between the test points: Control circuit terminal 86 and Ground circuit terminal 85.
  5. Ignition - On / Vehicle - In Service Mode
  6. Operate the component: Rear Defogger Switch - Pressed

    Verify the test lamp turns On and Off.

    • If the test lamp is always Off 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K33 HVAC Control Module
    3. Test for infinite resistance between the test points: Control circuit terminal 86 at Relay Socket and Ground
      • If less than infinite resistance - Repair the short to ground on the circuit.
      • If infinite resistance
    4. Test for less than 2 ohms between the test points: Control circuit terminal 86 at Relay Socket & Control circuit terminal 16 X2 at Control module harness
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Replace the component: K33 HVAC Control Module
    • If the test lamp is always On 
    1. Ignition/Vehicle - Off & Remove - Test lamp
    2. Disconnect the electrical connector: K33 HVAC Control Module
    3. Ignition - On / Vehicle - In Service Mode
    4. Test for less than 1V between the test points: Control circuit terminal 86 at Relay Socket and Ground
      • If 1V or greater - Repair the short to voltage on the circuit.
      • If less than 1V - Replace the component: K33 HVAC Control Module
    • If the test lamp turns On and Off  : Go to next step.
  7. Momentarily connect a 30A fused jumper wire between the test points: B+ circuit terminal 30 and Control circuit terminal 87

    Verify the component does not turn On and Off when connecting and disconnecting the jumper wire: E18 Rear Defogger Grid

    • If the component turns On and Off 

      Test or replace the component: KR5 Rear Defogger Relay

    • If the component does not turn On and Off  : Go to next step.
  8. Ignition/Vehicle & All vehicle systems - Off
  9. Install the component: KR5 Rear Defogger Relay
  10. Disconnect the electrical connector: X1 & X2 at E18 Rear Defogger Grid.
  11. Test for less than 10 ohms between the test points: Ground circuit terminal 1 X2 and Ground.
    • If 10 ohms or greater 
    1. Ground Connection - Disconnect
    2. Test for less than 2 ohms between the test points: Ground circuit terminal 1 X2 at Component harness and Ground Connection
      • If 2 ohms or greater - Repair the open/high resistance in the circuit.
      • If less than 2 ohms - Repair the open/high resistance in the ground connection.
    • If less than 10 ohms  : Go to next step.
  12. Connect a test lamp between the test points: Control circuit terminal 1 X1 and Ground circuit terminal 1 X2
  13. Ignition - On / Vehicle - In Service Mode
  14. Operate the component: Rear Defogger Switch - Pressed

    Verify the test lamp turns On and Off.

    • If the test lamp is always Off 

      Repair the open/high resistance in the circuit: Control Circuit

    • If the test lamp is always On 

      Repair the short to voltage on the circuit: Control Circuit

    • If the test lamp turns On and Off  : Go to next step.
  15. Test or replace the component: E18 Rear Defogger Grid
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